Reproductive ecology and distribution of deep-sea crabs (family geryonidae) : from southeast Florida and the eastern gulf of Mexico

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Reproductive ecology and distribution of deep-sea crabs (family geryonidae) : from southeast Florida and the eastern gulf of Mexico

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Title:
Reproductive ecology and distribution of deep-sea crabs (family geryonidae) : from southeast Florida and the eastern gulf of Mexico
Creator:
Erdman, Robert Bruce
Place of Publication:
Tampa, Florida
Publisher:
University of South Florida
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English
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xi, 147 leaves : ; 29 cm.

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Subjects / Keywords:
Crabs -- Reproduction ( lcsh )
Crabs -- Florida ( lcsh )
Crabs -- Mexico, Gulf of ( lcsh )
Dissertations, Academic -- Marine science -- Doctoral -- USF ( FTS )

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General Note:
Thesis (Ph. D.)--University of South Florida, 1990. Includes bibliographical references (leaves 125-137).

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University of South Florida
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Universtity of South Florida
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All applicable rights reserved by the source institution and holding location.
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027207021 ( ALEPH )
25835596 ( OCLC )
F51-00028 ( USFLDC DOI )
f51.28 ( USFLDC Handle )

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Graduate Council University of South Florida Tampa, Florida CERTIFICATE OF APPROVAL Ph.D. Dissertation This is to certify that the Ph.D. Dissertation of Robert Bruce Erdman with a major in Marine Science has been approved by the Examining Committee on March 6, 1990 as satisfactory for the dissertation requirement for the Ph.D. degree. Examining Committee: Major Professor: Norman J. Blake, Ph.D. Member: Peter R. Betzer, Ph.D. Member: John c. Briggs, Ph.D. Member: Joseph J Torres, Ph.D. Member: Gabriel A. Vargo, Ph.D.

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Robert Bruce Erdman All Rights Reserved 1990

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REPRODUCTIVE ECOLOGY AND DISTRIBUTION OF DEEP-SEA CRABS (FAMILY GERYONIDAE) FROM SOUTHEAST FLORIDA AND THE EASTERN GULF OF MEXICO by Robert Bruce Erdman A dissertation submitted for partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Marine Science in the University of South Florida April 1990 Major Professor: Norman J. Blake, Ph.D.

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ACKNOWLEDGEMENTS I would like to thank my major professor Dr. N.J. Blake for his patience, guidance and support throughout the course of my graduate studies. I would also like to acknowledge the members of my committee; Drs. P.R. Betzer, J.C. Briggs, J.J. Torres and G.A. Vargo for the their comments and advice. Special thanks are due Dick and Richard Nielsen for their invaluable assistance in collecting the material examined from southeast Florida. I am also indebted to the captains and crews of the R/V Tommy Munro, R/V Bellows and R/V suncoaster for their cooperation in collecting the material examined from the Gulf of Mexico. David Camp and Phil Steele of the Florida Department of Natural Resources, Marine Research Institute provided many hours of conversation on "the meaning of crusties", for which I am especially grateful. My sincere appreciation also goes to the many others that contributed in various ways to the success of this research; Don Hesselman, Mike Moyer, Frank Lockhart, Dr. W.J. Lindberg, Dr. R.B. Manning, Steve Snyder, Harriet Perry, Dick Waller and Joe Donnelly. ii

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TABLE OF CONTENTS LIST OF TABLES v LIST OF FIGURES vi ABSTRACT ix CHAPTER 1. INTRODUCTION 1 CHAPTER 2. LITERATURE REVIEW 6 Bathyal Zonation 6 Study Organisms 7 Historical Deep-sea Crab Fisheries 13 CHAPTER 3. OBSERVATIONS ON THE SOUTHEAST FLORIDA FISHERY: CATCH CHARACTERISTICS, MORPHOMETRieS AND MOLTING 15 Introduction Materials and Methods Results Discussion CHAPTER 4. REPRODUCTIVE BIOLOGY OF CHACEON FENNER! FROM 15 1 7 24 36 SOUTHEAST FLORIDA 43 Introduction Materials and Methods Results Discussion CHAPTER 5. COMPARATIVE REPRODUCTION OF CHACEON FENNER! 43 45 47 63 AND Q. QUINOUEDENS FROM THE EASTERN GULF OF MEXICO 67 Introduction Materials and Methods Results Discussion iii 67 68 70 86

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CHAPTER 6. BATHYMETRIC AND GEOGRAPHIC DISTRIBUTION OF CHACEON FENNER! AND OUINQUEDENS IN THE EASTERN GULF OF MEXICO 97 Introduction Materials and Methods Results Discussion CHAPTER 7. OXYGEN CONSUMPTION OF CHACEON FENNER! AND 97 98 99 104 QUINQUEDENS 110 Introduction 110 Materials and Methods 111 Results 114 Discussion 116 CHAPTER 8. SUMMARY 122 LIST OF REFERENCES 125 APPENDIX 1. MATING BEHAVIOR OF CHACEON FENNER! IN CAPTIVITY 138 iv

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LIST OF TABLES Table 1. Molt stages of Chaceon fenneri based on external carapace condition. Adapted from Beyers and Wilke (1980) as presented for Q. maritae. 25 Table 2. Catch summary of male Chaceon fenneri harvested from commercial crabbing trips made during the period February through December, 1986. 26 Table 3. Linear and geometric mean (GM) functional regression equations of carapace length (CL) and weight (WT) on carapace width (CW) for male and female Chaceon fenneri. 32 Table 4. Developmental stages of ovaries of Chaceon fenneri including color variation and mean oocyte diameter by stage. 48 Table 5. summary of regression analysis of fecundity for Chaceon fenneri and Q. guinguedens. 83 Table 6. Bottom water temperature ("C) by area, season and depth including; annual mean temperature by area and depth, and seasonal mean temperature by month and depth. 100 Table 7. Results of statistical analyses on effects of area, season and depth on mean carapace width of female Chaceon fenneri. 103 Table 8. Routine respiration rates (V02 ) and Q10s of Chaceon fenneri and Q. guinguedens acclimated and measured at 6.0 and 12.0 c. 115 Table 9. Comparative routine respiration rates for large cold temperate shallow water crustaceans. 119 v

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LIST OF FIGURES Figure 1. Typical long line trapping gear used in deep-sea crab fisheries showing surface retrieval floats and ground line with attached traps. 18 Figure 2. Nielsen trap used in the Chaceon fenneri fishery. given in feet except for in inches. southeast Florida All dimensions are mesh size which is Figure 3. Map of Florida showing location of sample sites; SE represents the commercial fishing area off southeast Florida sampled monthly 20 from February, 1986 through January, 1987. 23 Figure 4. cumulative size frequency distribution of male and female Chaceon fenneri collected during the period of February, 1986 through January, 1987 from southeast Florida. 28 Figure 5. Monthly size frequency distributions of male Chaceon fenneri from southeast Florida. 30 Figure 6. Cumulative weight frequency distribution of male and female Chaceon fenneri collected during the period of February, 1986 through January, 1987 from southeast Florida. 33 Figure 7. Monthly size frequency distributions of female Chaceon fenneri showing molt stages. 35 Figure 8. Early stage ovary of Chaceon fenneri with germ strand (GS), oogonia (OG), and early stage oocytes (OC) radiating out from germ strand (X 25). 50 Figure 9. Intermediate stage ovary of Chaceon fenneri with accumulating yolk globules (Y) within developing oocyte and accessory cells (AC) surrounding oocytes entering early vitellogenesis (X 160). 51 vi

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Figure 10. Mature ovary of Chaceon fenneri with prominent nucleus (N), yolk globules (Y), and chorionic membrane (M) of mature ovum (X 160). 53 Figure 11. Redeveloping ovary of Chaceon fenneri with developing oocytes (0) radiating from the germ strand and numerous phagocytic cells (P) surrounding unspawned ova undergoing resorption (RO) (X 63). 54 Figure 12. Monthly size frequency distributions of female Chaceon fenneri collected from southeast Florida, including number of individuals (N) and mean carapace width (CW) 56 Figure 13. Monthly ovarian stages of Chaceon fenneri collected from southeast Florida. Key to ovarian stages is shown in the figure. 57 Figure 14. Mean oocyte diameter of Chaceon fenneri by month of sample including standard deviation and oocyte diameter range. Triangles represent size of extruded eggs. 58 Figure 15. Relationship in Chaceon fenneri of brood size on carapace width as described by: number of eggs= 4,465.7CW-346,105. 60 Figure 16. Cumulative size frequency distribution of 347 female Chaceon fenneri collected from southeast Florida. Solid areas indicate ovigerous females. 62 Figure 17. Quarterly ovarian stages of Chaceon fenneri by depth of sample. Key to stages is shown in the figure. All depths are in meters. 72 Figure 18. Quarterly size frequency distributions of female Chaceon fenneri by depth of sample. 74 Figure 19. Quarterly mean oocyte diameter of Chaceon fenneri by depth of sample, including standard deviation and oocyte diameter range. 76 Figure 20. Quarterly ovarian stages of Chaceon guinguedens collected from 677 meters. Key to stages is shown in the figure. 78 vii

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Figure 21. Quarterly size frequency distributions of female Chaceon guinguedens collected from 677 meters in Areas 1 and 2. 81 Figure 22. Quarterly mean oocyte diameter of Chaceon guinguedens collected from 677 meters, including standard deviation and oocyte diameter range. 82 Figure 23. Biennial reproduction model proposed for Chaceon fenneri and guinguedens. 93 viii

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REPRODUCTIVE ECOLOGY AND DISTRIBUTION OF DEEP-SEA CRABS (FAMILY GERYONIDAE) FROM SOUTHEAST FLORIDA AND THE EASTERN GULF OF MEXICO by ROBERT BRUCE ERDMAN An Abstract Of a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Marine Science in the University of South Florida April 1990 Major Professor: Norman J. Blake, Ph.D. ix

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ABSTRACT Monthly samples of Chaceon fenneri collected from southeast Florida indicate an annual reproduction cycle with a single batch of eggs produced each year. Oviposition begins in late August and continues through October with eggs retained for approximately six months until hatching during late February and March. Fecundity estimates range from 131,000 to 347,000 eggs with brood size correlated to carapace width. Changes in gonopore margins associated with molting and the onset of ovarian activity indicate that size at sexual maturity is between 85 and 100 mm carapace width. Quarterly samples of fenneri and quinquedens collected from 311 to 494 m at five geographic areas in the eastern Gulf of Mexico indicate that each species is bathymetrically segregated on the continental slope. Chaceon fenneri predominates between depths of 311 and 494 m while quinquedens is restricted to depths of 677 m or greater. Water temperatures recorded at each depth suggest that the bathymetric distribution of each species may be temperature dependent. However, the presence of fenneri on coarse substrate and quinquedens on soft substrate also indicates that substrate requirements may differ between species. X

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Analysis of the reproductive cycle of each species indicates that both species show a pronounced annual cycle. oviposition in quinquedens occurs between May and August, three months earlier than in fenneri. Larvae of both species hatch during February and March. Differences in the duration of reproductive events may relate to the segregated bathymetric distribution of each species. The incidence of molting females and non-ovigerous females observed during the breeding season suggests that although both species reproduce annually on the population level, individuals may reproduce biennially. Although the bathymetric distribution of each species appears temperature related, measurements of routine respiration rates at 6 and 12 c showed no interspecific differences in oxygen consumption. Routine respiration rates of both species are comparable to shallow water cold temperate crustaceans of equivalent sizes. Abstract approved: xi Norman J. Blake, Ph.D. Professor Department of Marine Science Date of Approval

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CHAPTER 1. INTRODUCTION The continental slope along with the continental rise comprise the bathyal zone of the marine benthos. This zone is considered the major transitional zone between the physically variable continental shelf environment and the physically stable deep sea (Menzies et al, 1973). Generally accepted bathymetry places the upper limit of this zone at 200 m extending to a lower limit between 2000 and 3000 m. Major changes in physical characteristics include decreases in light, temperature and food availability, and an increase in hydrostatic pressure, all of which have a major influence on the biology of organisms that inhabit this region (Somero, 1982; Somero et al, 1983). In the absence of sufficient light for photoautotrophs, the inhabitants of the slope region are dependent upon various forms of particulate organic matter that are primarily allochthonous in nature. These include: planktonic material such as exuviae and fecal matter, deadfalls of large nekton, macrophyte debris, and terrigenous material. Autochthonous production is limited to chemoautotrophs; however their contribution is small compared to allochthonous sources (Rowe and Staresinic, 1979)

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As a consequence of the dependence upon externally derived energy sources, biomass declines exponentially with increased depth (Rowe and Menzel, 1971; Rowe et al, 1982; Rowe, 1983). Although regional variations have been noted in both overall biomass and the rate of decline with increased depth (Rowe et al, 1974), these differences have been correlated with surface production, the width of the adjacent continental shelf and latitude (Rowe, 1983). Nevertheless, organisms that inhabit greater depths have adapted to survive where low food availability is a potential limiting factor. 2 The physiological rates of deep living organisms also show a decline with increased depth (Childress, 1975; Smith and Teal, 1978; Torres et al, 1979; Donnelly and Torres, 1988). This has been attributed both to the reduced temperatures and the paucity of food characteristic of greater depths. these factors have major ramifications in the "design" of deep-living organisms (Somero, 1982; Somero et al, 1983). In particular, growth rates and activity levels associated with feeding strategies are greatly reduced when compared to shallow-living species (Somero et al, 1983; Rowe, 1983). An important component of continental slope fauna are organisms operationally referred to as megafauna [organisms readily visible in photographs (Grassle et al, 1975)]. Although this definition permits the inclusion of a wide variety of organisms, three groups are generally recognized

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3 as dominant based on abundance and biomass: demersal fishes, decapod crustaceans and echinoderms (Haedrich et al, 1975, 1980). In general, megafauna display opportunistic scavenger/predator feeding strategies. Thus, where mobility may aid in the location of unpredictable food items, large size may be selected for (Haedrich and Rowe, 1977; Polloni et al, 1979). Current data also suggests that megafauna biomass is greater than that expected in a typical Eltonian pyramid (Haedrich and Rowe, 1977; Rex, 1983). This is presumably the result of megafauna utilizing additional sources of food besides smaller benthic organisms. Crabs of the family Geryonidae are important members of the continental slope megafauna (Polloni et al, 1979; Haedrich et al, 1975, 1980). These large brachyurans are distributed throughout the Atlantic, Indian and Pacific Oceans and inhabit a wide range of depths between 200 and 2000 m (Rathbun, 1937; Manning and Holthuis, 1989). Of the three dominant groups of slope megafauna, geryonid crabs are often among the top ten numerically dominant species and may comprise greater than fifty percent of megafaunal biomass (Polloni et al, 1979; Haedrich et al, 1975, 1980). Thus, they play an important role in the trophic structure of benthic communities on the continental slope (Rex, 1976, 1981) The biology of megafauna such as Geryon spp. and Chaceon spp. has not been investigated quantitatively due to their patchy and widespread distribution on the continental

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slope (Rowe and Haedrich, 1979). Previous studies have often been limited by sampling constraints, although the recent combined use of trawls, traps, photography and submersibles has led to a significant increase in our knowledge of continental slope fauna, especially megafauna. Nevertheless, specific information on the biology of many 4 slope inhabitants is meager. In light of recent interest in the potential exploitation of mineral and fishery resources at the limits of continental margins, it has become crucial to increase our knowledge of life histories, reproduction patterns, trophic relationships and population structures of continental slope fauna (Rowe and Haedrich, 1979). The object of this research was to examine aspects of the reproductive biology of the newly recognized deep-sea golden crab, Chaceon fenneri. Cooperative efforts with the commercial fishery off southeast Florida permitted time series data collection on molting and reproduction patterns. This sampling program also provided data on morphometries and ongoing fishing trends. A comparative study was also conducted on the reproductive biology, and geographic and bathymetric distribution of fenneri and its congener guinguedens from the eastern Gulf of Mexico. oxygen consumption rates were also determined for each species over their normal habitat temperature ranges to determine routine metabolic rates and to examine the potential effect of temperature on the bathymetric

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5 distribution of these large slope dwelling brachyuran crabs.

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CHAPTER 2. LITERATURE REVIEW Bathyal Zonation The benthic fauna of the continental slope has been considered transitional in nature with a gradual replacement in species with increased depth (Sanders and Hessler, 1969). There is a pronounced change in invertebrate feeding types from suspension feeders characteristic of sublittoral environments to deposit feeders which utilize the accumulated organic material present in the sediments (Blake and Doyle, 1983). Large mobile megafauna are usually opportunistic scavenger/predators and may exhibit extensive bathymetric distributions (Rex, 1976, 1981). 6 Recent studies suggest the presence of discrete faunal zones that are strongly correlated with depth such that characteristic dominant species and diversity gradients may be easily recognized (Rowe and Haedrich, 1979). These zones may extend horizontally along isobaths for great distances and are separated vertically by areas of rapid faunal change (Rowe and Menzies, 1969; Menzies et al, 1973; Haedrich et al, 1975, 1980). This zonation may be especially pronounced among dominant slope megafauna such as decapod crustaceans

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7 and demersal fishes (Menzies et al, 1973; Rowe and Haedrich, 1979) The basis for zonation on the slope remains unclear. Gray (1974) noted greater diversity associated with increased sediment heterogeneity. Thus, strong boundary currents which may influence slope sediment structure may also affect faunal zonation (Doyle et al, 1979; Mullins et al, 1988). Currents have also been suggested to affect egg and larval distribution patterns and the distribution of organic material along isobaths (Rowe and Menzies, 1969). The variation in the dispersal of organic material has also been proposed to affect zonation based on different feeding strategies which suggest greater trophic complexity and associated biological interactions (Rex, 1981, 1983). Finally, the presence of pressure sensitive enzymes that show greater activity at specific depths have been identified as potential physiological mechanisms that limit vertical zonation (Somera et al, 1983). Interestingly, the gradual decrease in temperature with depth has not been considered a major factor in the zonation of continental slope fauna (Rowe and Haedrich, 1979). Study Organisms The taxonomic placement of the genus Geryon has been subject to many different interpretations by carcinologists. Prior to the establishment of the monotypic family

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8 Geryonidae by Colosi in 1923, members of this genus had been included in the families Cancridae, Ocypodidae, Goneplacidae and Xanthidae (Manning and Holthuis, 1989). In recent years, it has been accepted that the Geryonidae show greater affinity with the family Portunidae (Leone, 1951; Manning and Holthuis, 1981) and the family has been placed with the Portunidae in the superfamily Portunoidea (Bowman and Abele, 1982). The status of the individual species of the genus Geryon has also been subject to great taxonomic confusion. Prior to 1980, only five species had been described and due to the absence of sufficient reference material, newly collected specimens were often misidentified with those species. For example, Geryon affinis, a large gold colored species from the northeast Atlantic Ocean was the commonly cited identity for all similar color forms regardless of the source of collection. A similar situation also existed for red colored forms which were identified as guinguedens (Manning and Holthuis, 1981). The resulting confusion suggested that the few species recognized had extensive geographical ranges and were often present on the continental slope on both sides of major oceans basins. By 1981, it was recognized that this family was more speciose than previously believed and a major effort to gather new material and re-examine old collections was initiated (Manning and Holthuis, 1981, 1984, 1986, 1987, 1988, 1989). During this fenneri was recognized

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as a new species distinct from the similar gold colored Q. affinis (Manning and Holthuis, 1984) and the identity of Q. maritae, a red colored form, was established as separate from Q. guinguedens (Manning and Holthuis, 1981). Other newly described species included: Q. chuni, Q. erytheiae, Q. gordonae, Q. granulatus and g. macphersoni (see Manning and Holthuis, 1989 for review). 9 A complete revision of the family Geryonidae was recently completed by Manning and Holthuis (1989) which restricts the family to three genera and 24 species. The genus Geryon Kryer, 1837 contains two species and is now limited to forms bearing three anterolateral teeth on each side of the carapace. The new genus Chaceon Manning and Holthuis, 1989 is restricted to species with five anterolateral teeth on the carapace margin and at present contains 21 species. The third genus Zariquieyon Manning and Holthuis, 1989 is at present monospecific. Thus, Geryon quinquedens and Q. fenneri have now become Chaceon quinguedens and fenneri respectively. In addition, eight new species of Chaceon were described: atopus, bicolor, crosnieri, eldorado, inglei, mediterraneus, notilis and sancthaehelenae (Manning and Holthuis, 1989). Two additional species have since been recognized; ramosae and chilensis (R.B. Manning, Smithsonian Institution, pers. comm.). Although the geographic range of many species remains unknown, members of the genus Chaceon are the most

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widespread and have been recorded from every major ocean with exception of the northeast Pacific. The genus Zariguieyon is at present restricted to the Mediterranean Sea while the two species of Geryon are limited to the northeast Atlantic Ocean. Four species of Chaceon are present in the northwest Atlantic Ocean; eldorado, inghami, fenneri and guinguedens, the latter two species endemic to the continental slope off the eastern coast of North America. Chaceon fenneri Manning and Holthuis, 1984 10 The golden crab, Chaceon fenneri, is a large gold or buff colored species inhabiting the continental slope of Bermuda (Luckhurst, 1986; Manning and Holthuis, 1986) and the southeastern United States from off Chesapeake Bay (Schroeder, 1959), south through the Straits of Florida and into the eastern Gulf of Mexico (Manning and Holthuis, 1984, 1986; otwell et al, 1984; Wenner et al, 1987). Prior to its description, previous records referred to this species as either the red crab guinguedens or the similar gold colored affinis, which is endemic to the northeast Atlantic Ocean (National Marine Fisheries Service, 1986; Manning and Holthuis, 1984). Its recognition as a new species was a direct result of exploratory fishing in the eastern Gulf of Mexico in hopes of establishing a new deepsea crab fishery in this area (Otwell et al, 1984).

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11 Reported depth distributions of fenneri range from 205 m off the Dry Tortugas (Manning and Holthuis, 1984) to 1007 m off Bermuda (Manning and Holthuis, 1986). Size of males examined range from 34 to 139 carapace length (CL) and females range from 39 to 118 mrn CL. ovigerous females have been reported during September, October and November, and range in size from 91 to 118 mm CL (Manning and Holthuis, 1984, 1986). Chaceon guinguedens Smith, 1894 The red crab Chaceon guinguedens has been the object of limited commercial fishing off the Canadian maritime provinces and the New England states since the late 1960's (Gerrior, 1981). This species has an extensive geographic range inhabiting the continental slope from Nova Scotia (McElman and Elner, 1982) south along the continental United States, including the Gulf of Mexico (National Marine Fisheries Service, 1986; Pequegnat, 1970). Reports of this species from Uruguay (Juanico, 1973), Argentina (Scelezo and Valenti, 1985), and Chile (Retamal, 1977; Chirino-Galvez, 1985) are in error and have proven to be new species (Manning and Holthuis, 1989). Depth distribution of guinguedens ranges from 135 m to 2130 m. Segregation by sex and depth is well documented. Females are common at depths that range from 300 to 600 m while males predominate at depths in excess of 500 m (Gray,

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12 1969; Haefner and Musick, 1974; Haefner, 1978; Wigley et al, 1975). Size also varies with depth, with larger individuals reported from shallower depths (Haefner and Musick, 1974; Haefner, 1978; Wigley et al, 1975). The depth distribution of guinguedens changes dramatically south of Cape Hatteras, including the Gulf of Mexico. The upper bathymetric limit decreases from 135 to 677 m (Soto, 1985; Lockhart, 1988), which indicates a pattern of isothermal submergence. The restricted depth range is proposed to be dependent on the 10 c isotherm, which is present at shallower depths in the cold temperate region of the northeast United States (Soto, 1985). Reproduction of guinguedens is reported to be continuous, with ovigerous females present year round (Gray, 1969; Haefner, 1977, 1978). A peak spawning season is suggested in the winter months. However, evidence is based only on color changes of developing eggs and changes in gross ovarian condition. Ovigerous females are concentrated at the upper limits of their depth distribution, presumably utilizing the somewhat warmer waters to enhance egg development (Haefner, 1977). size at sexual maturity of female crabs is between 80 and 91 mm carapace width (Haefner, 1977). Planktotrophic larvae have been described by Perkins (1973) and mating, which occurs after female molting, has been reported by Elner et al (1987). Other aspects of the biology of guinguedens have been examined including nutritional flexibility of larvae

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(Sulkin and van Heukelem, 1980), juvenile growth (van Heukelem et al, 1983), larval dispersal as affected by temperature and current patterns (Roskowski, 1979), the effect of fishing on stocks (Gerrior, 1981) and commercial processing techniques (Holmeson and McAllister, 1974). Historical Deep-Sea Crab Fisheries 13 Initial interest in the potential of a deep-sea crab fishery was a result of traditional New England trawlers moving farther offshore during the early 1950's in search of additional stocks of groundfish (Schroeder, 1959). Although the red crab, guinguedens, was often reported as incidental catch from these trawls, it was not until the early 1960's with the development of the deep-water lobster (Homarus americanus) fishery that interest was sufficient to justify research on the potential development of a deep-sea crab fishery off New England and the middle Atlantic states (Schroeder, 1959; McRae, 1961). Early fisheries-oriented research on guinguedens centered on broad scale geographic and bathymetric surveys, stock morphometries (Schroeder, 1959; McRae, 1961; Haefner and Musick, 1974; Wigley et al, 1975), onboard handling procedures (Meade and Gray, 1973) and product processing (Holmeson and McAllister, 1974). The species was initially harvested from Homarus americanus traps, with an exclusive crab fishery developing off Massachusetts during the early

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14 1970's. Male crabs greater than 114 mm carapace width were butchered at sea and further processed at shore-side plants into cocktail claws and picked meat. However, due to supply, processing and marketing problems, effort declined to only two vessels by 1981 (Gerrior, 1981). At present, only one vessel fishes exclusively for guinguedens off New England (P. Fulham, National Marine Fisheries Service, pers. comm.). Concurrent with the development of the New England fishery for guinguedens, studies on maritae began off western Africa (Dias and Machado, 1973; Le Loueff et al, 1974; Intes and Le Loueff, 1976). Commercial fishing rapidly followed, with a peak of 17 vessels in operation off western Africa by 1977 (Beyers and Wilke, 1980). Only male crabs greater than 110 mm carapace width were kept. However, as with the New England guinguedens fishery, product and marketing problems led to a decline in effort to only five vessels by 1982 (Melville-Smith, 1988). At present, the fishery for maritae is centered off South West AfricajNamibia and consists of five Japanese vessels. Current fishery practices are unregulated, consequently all crabs caught are utilized regardless of sex or size. The catch is initially processed at sea with the ex-vessel product of clusters and flake meat shipped to Japan for further processing (R. Melville-Smith, South African Sea Fisherie s Research Institute pers. comm.).

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15 CHAPTER 3. OBSERVATIONS ON THE SOUTHEAST FLORIDA FISHERY: CATCH CHARACTERISTICS, MORPHOMETRieS AND MOLTING Introduction The successful development and management of any commercial fishery requires that the target species life history is understood. Data of this nature are necessary so that responsible fishing practices and management decisions may be made to insure successful harvest without over-exploitation of the resource (Gulland, 1976). In view of recent interest in the commercial potential of deep-sea species, the acquisition of such life history data is even more critical, given our lack of knowledge of many such species. Important biological parameters include geographic and bathymetric distribution, size and weight relationships, reproductive biology especially as related to age and growth, minimum harvestable size and potential recruitment (Haefner, 1985). Equally important is monitoring ongoing fishery practices such that the effect of fishing may also be examined (Gulland, 1976; Melville-Smith, 1988). The recognition of fenneri as a new species (Manning and Holthuis, 1984) was a direct result of exploratory trapping efforts in the eastern Gulf of Mexico (Otwell et

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16 al, 1984). Interest in commercial exploitation developed rapidly with three vessels (two from New England and one from Alaska) initiating a trap fishery along the Florida west coast by late 1984. Male crabs were butchered, cooked and blast frozen at sea, with the final product of clusters, cocktail claws and picked meat prepared at shore side plants for marketing. However, due to marketing problems, compounded by distances greater than 100 miles to the fishing grounds, vessel and gear loss, and the absence of biological data, operations in the eastern Gulf of Mexico ceased by mid-1985. During late 1985, continued interest in the commercial potential of fenneri led to the initiation of exploratory fishing and research off Bermuda (Luckhurst, 1986), South Carolina (Wenner et al, 1987) and Georgia (D. Harrington, Georgia Sea Grant, pers. comm.). Additionally, in late 1985, a small fishery began off the southeast coast of Florida. Due to the close proximity of deep water, the catch from this fishery is delivered live to local markets rather than processed at sea. This nearshore fishery also permits fisherman to pursue additional commercial ventures rather than fish crab exclusively. Although two additional vessels have made recent attempts at establishing a fishery in the eastern Gulf of Mexico, the operations off southeast Florida remain the only successful fishery for fenneri in the southeast United States.

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17 Materials and Methods Trawl nets, characteristic of finfish and shrimp fisheries are unsatisfactory for crab fisheries due to the relative inefficiency of the net in capturing crabs and the adverse effect this method has on the catch (Gray, 1969; Haefner and Musick, 1974). Nets are also indiscriminate as to sex, size and molt stage of animals caught which may eventually contribute to overfishing (Haefner, 1985). Thus successful crab fisheries employ baited traps which are often adapted specifically for the target species. Trap use also permits selective culling of the catch so that undersize, molting or ovigerous animals may be returned to the water. Gear utilized by the deep-sea crab fisheries consists of deep-water long lines with more than 50 traps attached to a ground line which is weighted at each end (Figure 1). The ground line is connected by a float line (3:1 scope) to large floats and radar reflectors on the surface. This method requires the capability of retrieving and storing upwards of one mile of line from depths in excess of 300 meters (Otwell et al, 1984). A variety of trap designs have been utilized: New England lobster pots, Florida stone crab pots, Fathoms plus traps (Otwell et al, 1984; Wenner et al, 1987), Dungeness crab pots (R. Erdman, pers. cbs.) and beehive traps (Beyers and Wilke, 1980). I n general, three or four trap lines are fished in rotation with soak times

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Figure 1. DEPTH 200-500"' Typical long line trapping gear used in deepsea crab fisheries showing surface retrieval floats and optional grapnel. Trap types shown include: A. Dungeness, B. Beehive, C. stone crab, D. Nielsen, and E. Fathoms Plus. 18

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averaging 20-24 hours (Otwell et al, 1984; Melville-Smith, 1988). All past and present deep-water crab fisheries utilize deep-water long lines modified to suit local conditions and vessel capabilities. 19 Although the fishery for Q. fenneri off southeast Florida is also a traditional trap fishery, the close proximity of the continental slope (less than 10 miles) has led to the development of a different harvesting strategy which provides live rather than frozen product to local markets. Four to six large traps are attached approximately 140 to 180 meters apart to a ground line fitted with weights at each end. The large "Nielsen" traps measure 1. 8 m x 1. 2 m x 0.9 m and are made of steel round stock covered with 4 x 4 em stretch mesh (Figure 2). Traps are fitted with 12.7 em diameter escape rings and a large side door which provides easy access to the bait well and rapid removal of the catch. As the present nearshore fishing grounds are within commercial shipping lanes, and gear recovery is affected by the strength and variability of the Florida current, trap lines are deployed without the surface float system. Loran coordinates are recorded during deployment along with bottom profiles and relative position using shoreline landmarks. Trap recovery involves grappling for the ground line, with the vessel moving from offshore to onshore and the grapnel dragged perpendicular to the ground line (Figure 1). Recovery time for all deployed strings is variable depending on the strength and direction of prevailing nearshore

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FLOAT + BAIT WELL 3' 6' Figure 2. Nielsen trap used in the southeast Florida Chaceon fenneri fishery. All dimensions are in feet except for mesh size which is in inches. N 0

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21 currents. Four to six strings of traps may be fished with each string reset immediately after it is pulled. Male crabs greater than 130 mm carapace width are sorted from the catch and packed in crushed ice for delivery to market. All females and males less than 130 mm CW are immediately returned to the water. Soak times range between two and six days depending on market demand. Specimens of Chaceon fenneri were collected monthly from February, 1986 through January, 1987 via commercial trapping operations at approximately 26 10' N, 82 05' W, due east of Ft. Lauderdale, Florida (Figure 3). All sample depths were between 215 and 235 meters. Total number of crabs caught along with the number of traps pulled were recorded for each trip. Catch per unit effort (CPUE) in kilograms/trap was calculated for each trip based upon the total number of male crabs greater than 130 mm carapace width harvested. For morphometric data, crabs were randomly selected from the catch, packed in crushed ice and returned to the laboratory for analysis. For each crab, carapace width (CW, distance between the fifth lateral carapace spines) and carapace length (CL, midline distance from the diastema between the rostral teeth to the posterior edge of the carapace) were recorded to the nearest millimeter. Weight was measured to the nearest gram and missing appendages noted. Molt stages were estimated on a modification of stages presented by Beyers and Wilke (1980) for Q. guinguedens (probably Q. maritae, see Manning

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figure 3. of Florida and the eastern Gulf of Mexico location of sample sites. SE represents the coiTmercial fishing area off southeast Florida sampled from February, 1986 through January 1987. Numbers represent geographic areas quarterly from May, 1987 through February, 1988.

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. t I ' t ,. )' .: ....... ' I ... .. : '\ooom 0 (.) -X w u. 0 u. ..J :::) (!) 23

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24 and Holthuis, 1981) as shown in Table 1. Length-width (CL vs CW) and weight-width (WT vs CW) relationships were examined for each sex using linear and geometric mean (GM) functional regressions (Ricker, 1973). ANCOVA was utilized to test for differences in slopes and elevations of CL vs CW regressions between each sex (Sakal and Rolf, 1984). Only individuals missing no appendages and in the intermolt stage were used in morphometric analysis. ovigerous females were included in CL vs cw analysis but were not considered in WT vs cw relationships. Results Catch Characteristics Variation in local nearshore current patterns often prevented the recovery of all trap lines deployed. Consequently, soak times for each string of traps recovered were quite variable and ranged between 2 and 11 days. Thus, the catch data was insufficient for statistical analysis o f monthly trends in CPUE. However, the data collected did show a gradual decrease in CPUE, especially during the latter portion of the study period (Table 2). Concurrent with the decline in CPUE, there was also a noticeable decrease in the number of large male crabs greater than 150 m m CW. This decline in both overall numb ers of crabs and number of large males continued for three months after the

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25 Table 1. Molt stages of Chaceon fenneri based on external carapace condition. Adapted from Beyers and Wilke (1980) as presented for maritae. Hard (H) : Hard Old (HO) : Soft Old (SO) : Soft New ( SN) : Hard New (HN) : Intermolt stage; carapace hard and often heavily fouled with barnacles; blackened portions of carapace common due to abrasion and damage; color variable from bright gold to dirty light brown. Late intermolt stage; approaching molt; edges of carapace and appendages dark brown; distal margins of antennae and antennules pink or red. Immediate premolt stage; carapace and appendages dark brown or dark purple-brown; antennae, antennules and margins of mouthparts red or pink; epimeral suture along margin of carapace distinctly white or pink and soft to the touch; limb buds pronounced when present. Immediate post-molt stage; carapace soft and jelly-like; color ranges from bright gold to off-white. Approaching intermolt stage; carapace rigid yet brittle; may yield and crack easily under pressure; some fouling and blackened areas on carapace and appendages due to abrasion and damage during calcification; color bright gold or off-white.

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26 Table 2. Catch summary of male Chaceon fenneri harvested from commercial crabbing trips made during the period February through December, 1986. N represents the number of male crabs greater than 130 mm carapace width. Weight units are in kilograms and catch per unit effort (CPUE) units are in kilograms/trap. Month N Weight CPUE February 225 256 42.6 March 335 380 42.3 April 325 369 36.9 May 409 464 42.2 June 297 337 48.2 July 337 383 35.7 August 430 488 31.5 October 287 326 29.6 November 291 331 22.1 December 474 538 26.1

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27 present study was completed. At that time, all gear was retrieved and moved to equivalent depths farther south from the original fishing grounds (R. Nielsen, commercial fisherman, pers. comm.). Size and Weight Relationships Throughout the sampling period, the catch of male crabs greatly outnumbered that of females. Cumulative size frequency distributions of 508 male and 347 female fenneri examined (Figure 4) indicate a unimodal distribution for each sex with no suggestion of distinct year classes. Males are considerably larger than females, with overlap between the largest females and smallest males. Carapace widths of male crabs ranged from 111 to 190 mm with a mean CW of 158 mm, while females ranged from 89 to 156 mm CW with a mean cw of 123 mm. Animals smaller than 89 mm cw were not collected, possibly due to bias associated with trap design and the presence of escape rings. Fishing depths also precluded analysis of segregation by size with sex and depth as has been reported for other Chaceon species (see Beyers and Wilke, 1980; Gerrior, 1981; Intes and Le Loueff, 1976; Haefner, 1978 and Wenner et al, 1987) Monthly size frequency distributions of male fenneri are shown in Figure 5. Monthly mean carapace widths ranged between 152 and 162 mm; however, the incidence of smaller males decreased beginning in July 1986, coincidental with

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w 25 (.) z w 20 a: a: :::> 15 (.) (.) 0 10 m 5 (.) a: w a.. --D (j' N=508 D 9 N=347 ..-r. I--.-.--r-:-t--,....-f--f--f--. .-f.-,__ --rr ..:__ 1--I I I I T T I 90 100 110 120 130 140 150 160 170 180 190 CARAPACE WIDTH (mm) 28 Figure 4. Cumulative size frequency distribution of male and female Chaceon fenneri collected during the period of February, 1986 through January, 1987 from southeast Florida. N represents the number of individuals examined.

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29

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Figure 5 Monthly s ize frequency distributions on male Chaceon fenneri from southeast Florida, including number of individuals (N) and mean carapace width (CW).

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w (.) z w a: 2S 25 25 25 a: 25 ::::::> (.) (.) 0 25 w (.) a: w a. 25 2S 2S 25 r-___.:__!..---L..LLJ.....Ll..l__l_lj_L_ FEB 1986 N=30 CW=160 MAR N=40 CW=152 APR N=45 CW=155 !! u..:...L I r-n. I c_r-; 110120 130 1!50 180170 180 1&0 CARAPACE WIDTH (mm) MAY N=94 CW= 155 JUN N=47 CW= 152 JUL N=49 CW=159 AUG N=49 CW= 160 OCT N=53 CW= 162 NOV N=52 CW=160 DEC N=49 CW=158 30

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31 the fitting of escape rings in all traps. Although the present data set precludes statistical analysis of the effect of escape rings, the absence of smaller males and females in the overall catch was apparent following installation of escape rings in all traps. This suggests that smaller individuals may exit the trap once all bait is consumed. Morphometric relationships of CL vs cw were based on 262 males and 193 females. Linear and GM functional regression equations for each sex are shown in Table 3. ANCOVA indicated no significant differences between male and female CL vs CW equations (p<0.05), therefore linear and GM functional regression equations of CL vs CW were calculated for both sexes combined (Table 3). The weight frequency distribution of 262 males and 136 non-ovigerous females is shown in Figure 6. Weight of male crabs greatly exceeded that of females, ranging from 280 to 1930 g, with a mean weight of 1116 g. Mean weight of females was 449 g, ranging from 207 to 800 g. Although weights of both sexes show a unimodal distribution, the greater incidence of females in a narrower range of weight classes is due to the variation in body weight associated with the various phases of oogenesis. Because of obvious size differences between sexes, WT vs CW relationships were calculated separately for each sex and are shown in Table 3.

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32 Table 3. Linear and geometric mean (GM) functional regression equations of carapace length (CL) and weight (WT) on carapace width (CW) for male and female Chaceon fenneri. size units are in mm and weight units are in gm. All linear regression equations are significant at p<0.05. Linear eguation N GM equation Males CL = -5.99 + 0.81CW 262 0.89 CL = -14.30 + 0.92CW WT = -2132.45 + 20.64CW 262 0.87 WT = -2369.34 + 22.15CW Females CL = -4.28 + 0.86CW 193 0.88 CL = -13.19 0.93CW WT = -790.63 + 9.92CW 136 0.87 WT = -877.09 -10.62CW Combined sexes CL = -5.19 + 0.86CW 455 0.95 CL = -8.61 + 0.88CW

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w (.) z w a: a: = (.) (.) 0 1z w (.) a: w c.. -OcyN=262 BEJ 9 N=136 I I I I I I I I 200 400 600 800 1000 1200 1400 1600 1800 2000 WEIGHT (g) Figure 6. Cumulative weight frequency distribution of male and female Chaceon fenneri collected during the period of February 1986 through January, 1987 from southeast Florida. N represents the number of individuals examined. 33

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34 Molting No discernible molting pattern was observed for male fenneri. Fewer than 3% of the 508 crabs examined were observed in the immediate premolt stage (SO), while less than 10% showed the clean bright gold carapace indicative of recent molting. Although asynchronous molting is possible, meat of butchered males shows a watery texture during March and April that suggests physiological changes occurring prior to the onset of molting (R. Nielsen, commercial fisherman, pers. comm.). No changes in external carapace condition were noted during this period. Conversely, female crabs showed two periods of molting activity. During August and October, 1986, 33% of females examined were in the immediate premolt stage (SO) (Figure 7). Premolt females ranged in size from 89 to 118 mm CW. Females in the immediate post-molt stage (SN) and early intermolt stage (HN) were collected during October through December. Size ranges of recently molted females was between 110 and 139 mm. Additional molting activity was also observed during January 1987, when 17% of females observed were in the premolt stage. carapace widths of premolt females was between 103 and 123 mm cw. This molt period was not as pronounced as that observed during late summer and early fall. However, recently molted females (stage HN) were present in the catch during the period of March through May

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w (.) z w a: a: :J (.) (.) 0 .... z w (.) a: w c.. FEB 1986 N=28 MAR N=30 APR N=32 MAY N=25 JUNE N=32 AUG N=34 NOV N=28 SOFT OLD DEC N=34 SOFT NEW JAN 1987 N=29 NEW IIII1 HARD OLD D HARD 35 80 90 100 110 120 130 140 50 160 Figure 7.. CARAPACE WIDTH (mm) Monthly size frequency distributions of female Chaceon fenneri showing molt stages. Key to each stage is given in the figure. N represents the number of individuals examined.

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1986, suggesting that these animals may have molted during the previous late winter or early spring. Discussion Size and Weight Relationships Morphometric relationships have been previously reported for three species of Geryonidae; Chaceon guinguedens, maritae and Geryon trispinosus (formerly 36 tridens, see Manning and Holthuis, 1987, 1989). All members of this family show pronounced sexual dimorphism with males considerably larger than females (Manning and Holthuis, 1981, 1989). Length-width and length-weight relationships of guinguedens have been noted by Gray (1969) and Haefne r ( 1978), respectively. Males of that species attain a maximum size of 165 mm CW and may weigh up to 1200 g. Maximum size of females is approximately 142 mm CW; individuals of this size may weigh up to 510 g. Le Loueff et al (1974) and Beyers and Wilke (1980) reported on morphometries of maritae off western Africa. That species is similar to guinguedens in both size and weight. Males may reach a maximum of 165 mm CW (Dias and Machado, 1973) and weigh up to 1650 g, while large females of 115 mm cw may weigh 375 g. Size and weight relationships have also b een reported for trispinosus (Hepper, 1971). Maximum size of males is

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less than 100 mm cw, which may account for the absence of commercial interest in that species. 37 Chaceon fenneri is considerably larger than the previously discussed species and may be the largest member of the Geryonidae (Manning and Holthuis, 1984, 1989). Males may reach a maximum size of 195 mm CW and weigh up to 1900 g. Although smaller, females may measure up to 165 mm cw with a weight of 760 g. Molting and Growth Although the data collected during this study was insufficient for the analysis of growth patterns of fenneri, a discussion of growth in deep-sea crustaceans is warranted due to the important biologica l and fishery implications. Growth is generally expressed as an increase with time in length, volume or weight (von Bertalanffy, 1938) In crustaceans, growth is discontinuous and involves a series o f molts ( ecdyses) during which the rigi d exoskeleton is shed and replaced by a new and larger one. However, this loss of integument results in the loss of all calcified structure s thereby pre v enting the analysis of annual rings in persistent structures such as the shells of mollusks and the otoliths of fish. A second complication is that many types o f tags are lost during molting, thus t a g and recapture studies mus t be planne d and e xecute d accordingly (Hartnell, 1982).

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38 The examination of growth in crustaceans encompasses the analysis of two major components; the molt increment or increase in size at each molt, and the intermolt period or time between successive molts. With increased size, the molt increment usually decreases and the intermolt period commonly increases (Kurata, 1962; Hartnell, 1982). However, between sexes, females generally show a more drastic change in the growth format at the onset of sexual maturity. This is usually attributed to the energetic cost of and the accompanying period of egg brooding (Hartnell, 1985). Besides changes associated with size, sex and maturity, environmental factors such as temperature, light and food supply have also been shown to affect the growth format of crustaceans (Hartnell, 1982). The majority of growth studies have been conducted under laboratory conditions where these determinants have been selectively controlled which further complicates analysis of actual growth in natural populations (Kurata, 1962). Studies of the latter type are few in number and are limited to tag and recapture studies of species where commercial fisheries provide significant returns (Haefner, 1985). Growth in deep-sea crustaceans is generally quite slow t 1 1985) Thls is not (Childress and Price, 1978; Roer e a surprising when one considers the low metabolic rates of deep-sea organisms as compared to those of species living elsewhere (Smith and Teal, 1973; Torres et al, 1979) The

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39 low rates of metabolic processes have been proposed as an adaptive response to the decrease in biomass and food supply that are characteristic of increased depth (Rowe, 1983}. In particular, slow growth in deep-sea crustaceans may be attributed to a decrease in the molt increment, an increase in the intermolt period, or a combination of both (Roer et al, 1985). Melville-Smith (1989) has developed a growth model for male maritae which indicates that growth in that species is extremely slow. The model is based on growth data from juvenile guinguedens (Van Heukelem et al, 1983}, and tag and recapture data of adult maritae greater than 50 mm CW collected from the commercial fishery off South West AfricajNamibia. In general, smaller males (50-100 mm CW} showed an intermolt period of between 0.5-2.0 years, while larger males (100-150 mm CW) exhibited interrnolt periods of between 3-5 years. The model also predicts age from the growth data and suggests that male maritae of 165 mm CW may be over 25 years old. The low numbers of premolt and post-molt fenneri observed in this study also suggests that growth in this species is quite slow. Females showed a greater incidence of molting activity than males, but total numbers of both sexes in the so, SN and HN stages comprised less than 12 percent of all individuals examined. Although fenneri reaches a greater maximum size than the majority of Geryonidae, the growth model developed for maritae may be

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40 applied in general terms. As the present minimum size of male Q. fenneri harvested by the commercial fishery is 130 mm CW, the model suggests that animals of this size enter the fishery in their sixteenth year. Larger males exceeding 170 mm CW may well be over 30 years of age. Fishery Implications The impact of unrestricted fishing of deep-sea crabs can best be seen in data from the maritae fishery off South West AfricajNamibia. Although the initial fishery expanded rapidly, by 1980 effort had declined to only five vessels (Beyers and Wilke, 1980). since unrestricted fishing began in 1980, CPUE has decreased from 11.46 kgjtrap to 9.29 kgjtrap by 1986. However, of greater significance is the drastic change in the composition of the catch observed during the same period. Whole sections, which are from crabs greater than 110 mm cw, have declined from 39 percent o f the total catch to only seven percent. Conversely, flake meat produced from crabs less than 110 mm CW, has increased from 61 percent to 93 percent of the total catch during the same period (Melville-smith, 1988). This change in catch composition illustrates that the unrestricted fishing practices currently utilized have significantly reduced the number of large maritae in the present fishing grounds. Of greater importance is the unknown effect on future recruitment that may result from

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41 the harvest of female crabs. Although CPUE data (kg/trap) is also available from the guinguedens fishery, differences in trap designs, soak times and effort preclude any comparison of the present fenneri fishery data with that previously discussed. However, the gradual decline in CPUE observed during the present study i s a reflection of the impact that a small scale fishery may have on stocks in a localized area. As present fishing depths are restricted to depths between 215 and 230 m, the data suggests that the present fishery may deplete the stock of large male crabs within a relatively short period of time. As the data presented herein is from a 3 to 5 mile long, north-south running corridor, the decline in catch is not surprising. Within three months after the completion of this study, fisherman noted the continued decline in catch and moved the gear to a new corridor farther south of the present fishing area. This pattern of trapping in one area and moving all gear when catch rates decline is still in effect (R. Nielsen, commercial fisherman, pers. comm.). Because fenneri attains a greater maximum size and w eight than other G eryonidae, interest in the further development of a fishery is warranted. However, the slow growth characteristic of many deep-sea crustaceans (Childress and Price, 1978) and maritae in particular (Melville-Smith, 1989) must b e conside r e d by bot h f i s heries management and commercial interests. Unrestricted fishing

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may lead to rapid depletion of the reproductively active stock, similar to that present in the maritae fishery. Thus, the current voluntary fishing practice of harvesting only male crabs greater than 130 mm CW may provide sufficient numbers of smaller sexually mature males to permit continued reproductive success. This is further enhanced by the release of all females from the catch. Escape rings may permit undersize crabs to exit traps, however, the impact of their use in the present fishery remains unknown. Although the small southeast Florida fishery for fenneri has been relatively successful, the longevity of this fishery at increased levels of effort remains unknown. 42

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CHAPTER 4. REPRODUCTIVE BIOLOGY OF CHACEON FENNERI FROM SOUTHEAST FLORIDA Introduction 43 Reproductive cycles of marine invertebrates may be classified as rhythmic or continuous. Rhythmic patterns, which may be weekly, monthly, annual or biennial, involve a distinct gametogenic cycle. This includes the production and release of gametes followed by a period of inactivity during which energy reserves accumulate and gonad tissue regenerates prior to the onset of the next successive cycle. Thus, most reproductively active individuals of a population will reproduce synchronously when environmental conditions are correct (Giese, 1959; Giese and Pearse, 1974). Precise timing requires that initiation and regulation of gonad development is in synchrony with changes in the external environment, leading to the production of new individuals during conditions which are most optimal for their survival (Sastry, 1975). Continuous reproduction implies a successive series of gametogenic cycles by each individual. As there is no synchrony between individuals, the population appears to be reproducing continuously with the regulation of gonad

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44 development varying among each individual (Giese and Pearse, 197 4) The reproductive cycle is affected by exogenous factors such as temperature, photoperiod, salinity, and food supply. Temporal changes in these factors act as "zeitgebers" (triggers) that synchronize gametogenesis such that reproduction occurs under favorable conditions (Giese and Pearse, 1974). Considering the environmental consistency of the deep sea, continuous reproduction patterns are expected (Thorson, 1950; Scheltema, 1972). This pattern had been reported in a variety of deep-sea invertebrates: brachiopods (Rokop, 1974), bivalve mollusks (Sanders and Hessler, 1969; Rokop, 1974), isopods (Sanders and Hessler, 1969; Rokop, 1977), amphipods (Rokop, 1977), decapods (Haefner, 1977; Tyler et al, 1985; Melville-Smith, 1987c), and ophiuroids (Rokop, 1974; Grant, 1985). In virtually all of these studies, the absence of seasonality has been proposed to be responsible for the continuous patterns observed. Annual reproductive patterns in the deep sea have only been reported for a few species of bivalve mollusks (Lightfoot et al, 1979), isopods (George and Menzies, 1967, 1968), decapods (Hartnell and Rice, 1985) and ophiuroids (Schoener, 1968; Lightfoot et al, 1979). However, the data presented have often been questionable (presence/absence of ovigerous females; George and Menzies, 1967, 1968) and the recognition of specific "zeitgebers" has proven to be quite difficult if not impossible.

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45 Although continuous reproduction may predominate in the deep sea, comprehensive data on many deep-sea invertebrates remains scarce. Certain species may show annual patterns, yet it is obvious that the mode of development, evolutionary history, phylogenetic status and trophic dynamics of the species in question must be examined to ascertain the significance of this type of reproduction pattern in the deep sea. Materials and Methods Samples of female fenneri were collected monthly from the southeast Florida commercial fishery during the period of February 1986 through January 1987. The sample site and collection methods have been previously outlined in Chapter 3. For analysis of the reproduction cycle, female crabs were randomly selected from the catch, packed in crushed ice and returned live to the laboratory. Morphometric measurements and estimates of molt stages were recorded as described in Chapter 3. Additional characteristics such as the degree of carapace fouling by the barnacle Poecolasma sp. (R. Williams, University College of Swansea, pers. comm.), and gonopore size and shape were also recorded for each individual. The presence and color of extruded eggs were recorded along with the incidence of egg remnants on the pleopods. E h removed from each of 5 females and ac month, 25 eggs were

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46 the diameters measured with an ocular micrometer. Evidence of copulation was determined by examination of gonopore margins and spermatheca contents. Twelve females with stage C eggs (eye pigment visible; see Meredith, 1952) were examined for fecundity following methods adapted from Hines (1982). Pleopods with attached eggs were removed and fixed in 10% buffered Formalin. After drying to constant weight at 60 c, the eggs were removed from the pleopods, carefully stripped of any connective tissue, and weighed to the nearest 0.1 mg. Fecundity was estimated by extrapolation using the mean weight of 5 subsamples of 1,500 eggs and the dry weight of the total egg mass. The relationship between fecundity and carapace width was examined by linear regression (Zar, 1974). All females were dissected to examine gross ovarian condition with representative samples prepared for histological examination as described by Yevich and Barszcz (1977). ovarian tissues were fixed for 20-24 hours in ZenkerjHelly's solution, placed in cassettes and washed in a self-siphoning water bath for 24 hours. Tissues were then processed in an Autotechnicon Duo tissue processor through six changes of S-29 dehydrant, three changes of UC-670 clearing agent and two changes of liquid Paraplast. Following embedding in Paraplast, representative sections were cut at 6-8 on a Spencer rotary microtome. The resulting slides were stained with hematoxylin and eosin (Luna, 1960) and examined with a Zeiss Photomicroscope III.

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47 Developing oocytes were measured to the nearest micron on an image analysis system, consisting of a zeiss compound microscope equipped with a video camera, a Houston Instruments digitizing tablet, and an IBM microcomputer with analytical software. Monthly mean oocyte diameters were calculated from the measurements of 50 oocytes per individual using 14-22 animals per month. Results Ovarian Development The ovary is similar in location to that of most brachyurans. H-shaped in form, it lies dorsal to the hepatopancreas and extends posteriorly along each side of the hind-gut. Spermethecae, which arise from the midlateral portion, extend ventrally to gonopores that open on the sixth thoracic segment. Anterior to the heart, the ovaries join at a commissure just posterior to the stomach, with lobes that extend anterolaterally around the gastric region. The entire ovary is bound by fibrous connective tissue which serves to separate the organ from the surrounding hemocoel. Stages of ovarian development are presented in Table 4. The immature ovary is white or transparent, less than 2 mm in diameter, tubular, and w ithout pronounced lobation. Histologically, the m edial germ strand is surrounde d by abundant fibrous connective tissue and open spaces in the

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48 Table 4. Developmental stages of ovaries of Chaceon fenneri including color variation and mean oocyte diameter by stage. Mean diameters for each developmental stage were calculated from the measurement of 250 oocytes. ovarian stage Immature Early Intermediate Advanced Mature Redeveloping/ spent Color white transparent ivory yellow yellow-orange yellow-orange brown-orange brown-tan red-orange brown-tan purple-gray purple purple-gray dark purple ivory tan yellow-orange Oocyte diameters Cgm) Mean Range 83.9 30.6 -89 154.8 30.6 -352 243.3 96.3 -354 387.8 110 -535 89.4 22.1 -188

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49 lumen. When visible, oogonia are in close proximity to the germ strand. The early stage ovary is characterized by an ivory, yellow or yellow orange color. Oocytes in various stages of early development are present, often bound by fibrous connective tissue to form small internal lobes. The germ strand is well defined, with oogonia and early stage oocytes that radiate outwards and gradually fill the open spaces in the lumen (Figure 8). Mean oocyte diameter at this early stage is 83.9 with a range of 30.6 to 224 The intermediate stage ovary is a yellow-orange, brownorange or brown-tan color. Advanced oocytes, many which are entering the early stages of vitellogenesis, predominate at this stage. Numerous accessory cells are present and surround oocytes that are accumulating yolk globules (Figure 9). Mean oocyte diameter at this stage is 154.8 and developing oocytes range from 30.6 to 352 The advanced ovary is swollen with pronounced lobation, often obscuring the anterolateral portions of the hepatopancreas. Color varies from red-orange to brown-tan, gradually becoming purple-gray and purple in the latter portion of this stage. The majority of oocytes are in the late phases of vitellogenesis and exhibit a granular texture arising from the accumulation of yolk globules. Accessory cells peripheral to oocytes are still present in the early vitellogenic stage. The oocytes have a mean diameter of 243.3 and range from 110 to 354

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Figure 8. Early stage ovary of Chaceon fenneri with germ strand (GS), oogonia (OG), and early stage oocytes (OC) radiating out from germ strand (X 160). 50

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Figure 9. Intermediate stage ovary of Chaceon fenneri with accumulating yolk globules (Y) within developing oocyte and accessory cells (AC) surrounding oocytes entering early vitellogenesis (X 160). 51

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52 Mature ovaries are gray-purple or dark purple and the greatly swollen anterior lobes completely obscure the underlying hepatopancreas, The enclosing fibrous connective tissue is tightly stretched, often to the point of bursting during dissection. Mature ova are easily visible through this outer tissue layer. Histologically, the ovary is dominated by mature ova which are granular in appearance due to the high concentration of yolk globules (Figure 10). Vitellogenesis is essentially complete at this stage and the chorionic membrane surrounding each ova is conspicuous. The germ strand is usually obscured by the tightly packed mature ova, and accessory cells are present only proximal to the few oocytes still undergoing vitellogenesis. Mean diameter of ova is 387.8 with the maximum size of 545 overlapping the sizes of initially extruded eggs (500-560 The spawned or redeveloping ovary is very flaccid and ivory, tan, or yellow-orange. Unspawned ova may be visible through the outer fibrous connective tissue. The germ strand is well defined and oogonia and developing oocytes radiate outwards from this region (Figure 11). The greater part of the ovary consists of fibrous connective tissue and hemal spaces containing blood cells and phagocytes. Mature unspawned ova undergoing resorption are often present surrounded by phagocytes.

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figure 10. Mature ovary of Chaceon fenneri with prominent nucleus (N), yolk globules (Y) and chorionic membrane (M) of mature ovum (X 160). 53

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Figure 11. Redeveloping ovary of Chaceon fenneri with developing oocytes (0) rad1at1ng from germ strand and numerous phagocytic cells (P) surrounding unspawned ova undergoing resorption ( RO) (X 6 3) 54

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55 Reproductive Cycle The monthly incidence of ovigerous females examined indicates an annual reproductive cycle with a single batch of eggs produced each year (Figure 12). oviposition begins in mid-August and continues through early October. Thirtythree percent of females collected in August were ovigerous and had spent/redeveloping ovaries, while 17% had mature ovaries prior to oviposition. In october, 29% were ovigerous with ovaries in either spent/redeveloping or early developmental stages, while 8% had mature ovaries (Figure 13) Eggs are light purple or burgundy after oviposition, gradually becoming dark purple and purple-brown prior to hatching. They are carried for approximately six months after which larvae hatch during late February and March. Seven percent of females examined in February and 57% from March had egg remnants on the pleopods. Larvae were hatched from two ovigerous females held in the laboratory during early March, but larval culture was not successful. Analysis of mean monthly oocyte diameter further illustrates the annual reproductive cycle of fenneri (Figure 14). The minimum oocyte diameter recorded in October coincided with the greatest incidence of ovigerous females with redeveloping and early stage ovaries. Mean monthly oocyte diameter gradually increased each month and reached a maximum during July, prior to the initiation of

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w (.) z w a: a: :::) (.) 8 1z a: 80 90100110120130140150160 CARAPACE WIDTH (mm) FEB 1986 N:o28 CW=12s.2s MAR N=30 CW=124.25 APR N=32 CW=1 26.oo MAY N=25 CW=1 25.70 JUNE N=32 CW=126.80 JULY N = 29 CW=128.40 AUG N=34 CW=114.ao OCT N= 46 CW=116. 0 NOV N=28 cw = 125.20 DEC N=34 cw = 124.50 JAN 1987 N=29 Cw = 119.50 OVIGEROUS 56 D EGG REMNANTS Figure 12. Monthly size frequency distributions o f female Chaceon fenneri collected from southeast Florida, 1ncluding number of individuals (N) and mean carapace width (CW)

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z w a: 80 a: 0 60 0 0 1-40 z w 0 20 a: w Q. J JASON OJ 1987 0 SPENT MATURE (]ADVANCED 57 INTERMEDIATE DEARLY Figure 13. Honthly ovarian stages of Chaceon fenneri collected from southeast Florida. Key to ovarian stages is given in the figure.

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58 a: UJ .,_ .--... UJ .. 500 I 0 I I CCI) 400 I s UJZ .,_o A >-a: 300 v M v p o200 v rz E .... < 100 UJ F M A M J J A s 0 N D J 1986 1987 MONTH OF SAMPLE Figure 14. Mean oocyte diameter o f Chaceon fenneri by month o f s ample including standard deviatio n and oocyte diameter size range. Triangles represent size o f extruded eggs.

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oviposition in August. Mean oocyte diameter of 188 2 recorded in August included both mature and spent/redeveloping ovaries. Fecundity 59 Mean egg diameter for fenneri is 540 at the time of oviposition. This increases with development to between 580 and 600 prior to hatching (Figure 14). Regression analysis of egg number on carapace width is shown in Figure 15. The number of eggs per female increased with increasing carapace width as described by: Number of Eggs = 4,465.7 CW 346,105 r2 = 0.64 Thus, the number of eggs extruded is directly correlated with the size of the female. Egg number for the twelve females examined ranged from 131,000 through 347,000. Size at Sexual Maturity In addition to the onset of ovarian development and the presence of extruded eggs, other characteristics must also be considered in the assessment of size at sexual maturity in brachyurans. Following the pubertal molt, the abdomen and gonopores show changes that are generally accepted as external morphological indications of sexual maturity and subsequent mating (Hartnell, 1969). Chaceon fenneri exhibits the simple pattern of

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60 r=O.BO 0 ('t) 0 )( en (!) (!) w u.. 225 0 200 c: w 175 CD 150 ::::> z 125 0 100 90 100 110 120 130 140 150 160 CARAPACE WIDTH (mm) Figure 15. Relationship in Chaceon fenneri of brood size on carapace width as described b y : number of eggs= 4,465.7CW-346,105.

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61 gonopores described by Hartnell (1967), with three distinct types recognized. Type A gonopores which are narrow and slit-like are present on sexually immature animals. Type B gonopores which follow the pubertal molt are elongate and ovoid in shape, while type C is a modification of type B differing only in that the gonopore is more elongate and gaping as a result of mating during the immediate post-molt period. In addition, type C gonopores often exhibit a blackened margin due to abrasion by the male pleopods during mating. Carapace width of the 347 females examined ranged from 89 to 156 mm. Eighty-five females were ovigerous (25%) and ranged in size from 97 to 147 mm CW (Figure 16). All ovigerous females examined exhibited type C gonopores (elongate and gaping) with 74% having blackened margins. Type C gonopores were also observed on non-ovigerous females ranging in size from 103 to 156 mm cw, with 60% of the females examined having sperm in the spermetheca. Thus type C gonopores appear indicative of sexual maturity and previous mating. However, non-ovigerous females with type C gonopores and empty spermetheca may have previously undergone mating and oviposition but have yet to molt and mate again. Twenty-six females ranging in size from 89 to 118 mm CW were observed in the immediate pre-molt stages during August and October. All individuals examined had ovaries in the immature or early developmental stage and had type A

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20 w N=3 4 7 ( 8 5) (.) 15 .OVIGEROUS tz z w w a: 10 (.) a: a: ::J (.) 5 (.) 0 90 100 110 120 130 140 150160 170 CARAPACE WIDTH (mm) Figure 16. Cumulative size frequency distribution of 347 female Chaceon fenneri collected from southeast Florida. Solid areas indicate ovigerous females. 62

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63 gonopores. Recently molted females collected during the period of October through December exhibited signs of recent mating. Seventy-one percent of females ranging in size from 105 to 120 mm CW had type C gonopores. Seven females were examined for spermetheca contents and five had sperm present. The remaining 29% of recently molted females had type B gonopores and empty spermetheca. Ovaries from all recently molted crabs were either in the early or intermediate stage of development. Considering the size ranges of ovigerous females, the stages of ovarian development, and changes in gonopore structure associated with the pubertal molt, size at sexual maturity of fenneri is between 85 and 100 mm CW. Discussion The annual reproductive cycle shown by fenneri is in sharp contrast to the continuous cycles reported for other species o f Chaceon. Chaceon maritae collecte d off South West AfricajNamibia, exhibited no reproductive seasonality based on visual and histological examination of the ovaries (Melville-Smith, 1987c). Ovigerous females were observed throughout the year; however they comprised less than 0.1% of the more than 9000 individuals examined. Although that specie s has a smaller maximum size than f enneri, the size t o cw) (Le Loueff e t al, 1974; a s exual matur1ty (80-10 mm Melville-Smith, 1987c) is comparable. Fecundity estimates

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64 maritae range between 107,000-350,000 eggs per brood, which is similar to fenneri over the size range of females examined (Melville-Smith, 1987c) Continuous reproduction has also been reported for guinguedens collected off the mid-Atlantic states (Haefner, 1977, 1978). Ovigerous females of that species have been collected throughout the year, but based on ovarian stages and seasonal differences in the developmental stages of brooded eggs, a peak spawning season was suggested during the fall months. However, Ganz and Hermann (1975) suggested that oviposition occurs in late July and August with eggs incubated for nine months until larvae hatch during May. Size at sexual maturity of Q. guinguedens is between 80-91 mm CW, which is similar to Q. fenneri and maritae. However, fecundity estimates of between 35,000210,000 eggs per brood are less than in the latter two species (Hines, 1982). The pronounced annual reproduction cycle observed in fenneri indicates the presence of subtle environmental changes which serve to synchronize the initiation of gametogenesis, onset of spawning and duration of larval development. current deep-sea reproduction studies indicate that annual cycles may be more common than previously supposed (Tyler et al, 1982; Tyler, 1988) It has been proposed that this type of pattern may be a response to increased food supplies correlated with seasonal pulses in surface productivity (Schoener, 1968; Tyler et al, 1 982 ;

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65 Hartnell and Rice, 1985). This may be especially true for deposit feeding organisms dependent upon the accumulation of organic material in the sediments. In particular, long term measurements of currents, particle flux and physical variation in the deep sea suggest a distinct and predictable annual periodicity in relatively restricted areas (Tyler, 1988). Tyler et al (1982) support this view but also suggest the non-adaptive retention of shallow water breeding patterns in species that have only recently extended their range to greater depths. The temporal incidence of ovigerous, non-ovigerous and molting females observed in this study suggest that although the population may reproduce annually, individuals may be on a biennial cycle. The incidence of non-reproducing females, and premolt and post-molt females during late summer and early fall was concurrent with the presence of spent/redeveloping ovaries and recently oviposited eggs in reproductively active members of the population. As mating follows molting in this species (see Appendix 1), females that molt and mate during late summer and early fall would not undergo oviposition until the following year. The early and intermediate stages of ovarian development observed in recently molted females supports this hypothesis. Delayed oviposition following mating may also apply to females that lt d 1 Although ovarian stages did not mo ur1ng ear y spr1ng. entirely support this, females that molt during that period may undergo oviposition during october rather than August.

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66 The biennial reproductive cycle suggested for g. fenneri conforms to the low frequency of reproduction (LFR) model proposed by Bull and Shine (1979). Iteroparous species that conform to this model reproduce annually on the population level but biennially on the individual level. Alternate years of the cycle involve reproduction related accessory activities such as migration (Bull and Shine, 1979} or molting (Somerton and Macintosh, 1985). Molting is risky and subjects the individual to increases in physiological stress and vulnerability to predation. As molting and reproduction are competing processes under neuro-endocrine control, energy reserves must be cycled accordingly (Adiyodi, 1985; Hartnell, 1985). Therefore, by utilizing the LFR pattern, the risk and energetic cost of molting is incurred half as often and the energy needed for reproduction may be accumulated for twice as long (Somerton and Macintosh, 1985}. When one considers the limited energy resources characteristic of the deep sea (Rowe, 1983} and the slow growth characteristic of the Geryonidae (MelvilleSmith, 1989}, the evolution of the LFR strategy may reflect successful adaptation for survival in this environment.

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67 CHAPTER 5. COMPARATIVE REPRODUCTION OF CHACEON FENNER! AND Q. QUINQUEDENS FROM THE EASTERN GULF OF MEXICO Introduction Both Chaceon fenneri and guinguedens are present on the continental slope of the eastern Gulf of Mexico. Each species is segregated by depth with little overlap in bathymetric distribution; fenneri is present at upper slope depths between 348 and 787 m, while guinguedens is restricted to depths in excess of 677 m (Lockhart, 1988). This species normally inhabits depths between 150 and 900 m off New England and the Canadian Maritime provinces (Haefner and Musick, 1974; Wigley et al, 1975; McElman and Elner, 1982) The intermediate slope distribution shown by Q. guinguedens in the eastern Gulf of Mexico is consistent with the pattern of isothermal submergence shown by this species throughout its range south of Cape Hatteras (Soto, 1985). Isothermal submergence is also shown by other cold temperate shelf and slope species that have extended their range to more warm temperate regions (Briggs, 1974; Nations, 1979). As cold temperature isobaths are found at greater depths at low this distribution pattern appears

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68 strongly temperature dependent. The presence of two congeneric species in a bathymetrically segregated distribution implies that subtle environmental triggers would have a greater impact on the reproductive cycle of the species with the upper slope distribution. Therefore, Gulf of Mexico populations of fenneri would be expected to show an annual reproductive cycle similar to that observed off southeastern Florida. Although the previous study (Chapter 4) confirmed an annual cycle in this species, samples were limited in depth and geographic area. The lower slope distribution of guinguedens in the eastern Gulf of Mexico would infer that environmental signals would be greatly dampened and that this species would retain the continuous reproductive cycle reported by Haefner (1977, 1978). If the protracted annual cycle suggested by Ganz and Hermann (1975) is indeed present, that cycle combined with expected slow growth would suggest that the low frequency of reproduction pattern proposed for fenneri may also apply to guinguedens. Materials and Methods Quarterly sampling was conducted from May 1987 through February 1988 at five geographic areas in the northeastern Gulf of Mexico (Figure 3). Depth zones o f 311, 494 and 677 m were sampled at each location. Sampling procedures

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69 utilized deep water trap lines adapted from gear illustrated by Otwell et al (1984). Six Nielsen traps (see Chapter 3) were deployed on each trapline with soak times ranging from 17 to 24 hours. Approximately 10 kg of mullet (Mugil cephalus) was used as bait in each trap. To determine the upper distributional limit of g. fenneri, traps were set at depths of 147 and 210 m in Areas 4 and 5 during August. Additional trap sets were also made during May (Area 4, 311 m) and August (Area 5, 494 m) to collect animals for tagging purposes. Although no tagged animals were recaptured, data from female crabs collected from these sets were included in analysis of reproductive patterns. Data analysis for each crab included morphometric measurements, estimation of molt stages, degree of carapace fouling, presence of eggs or egg remnants and examination of gonopore size and shape. Procedures for these analyses have been discussed in Chapters 3 and 4. When sample size permitted, at least 20 females of each species from each area and depth zone were dissected to examine gross ovarian condition. Representative samples were prepared for histological examination as outlined in Chapter 4. For each species, mean oocyte diameters by season, area and depth were calculated following procedures outlined in the previous chapter. Fecundity estimates were based on egg counts from 22 g. fenneri and 11 g. guinguedens following methods adapted h t 4 Eggs examined from Hines (1982) as presented 1n C ap er

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70 from fenneri were in developmental stage c (eye pigment visible) while those of guinguedens were in developmental stage B (body segmentation visible) (see Meredith, 1952). The relationship between fecundity and carapace width was examined by linear regression analysis for each species (Zar, 1974). ANCOVA was utilized for comparisons of fecundity between species with egg number as the covariate (Sokol and Rolf, 1981). Results A total of 1438 female fenneri and 765 female guinguedens were collected throughout the study period, with each species showing distinct bathymetric and geographic distribution patterns. Chaceon guinguedens was collected at all five geographic areas sampled but was restricted to depths of 677 m. Conversely, fenneri was present only at the southernmost stations (Areas 4 and 5), but was recorded at all depths between 311 and 677 m. No fenneri were recorded from depths of 147 m and only one individual was collected from 210 m. Numerical abundance of this species was greatest at depths of 311 and 494 m; only 37 individuals were collected from 677 m. Additional data on the bathymetric and geographic distribution of each species will be discussed in Chapter 6.

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71 Reproductive Biology Chaceon fenneri Examination of 353 fenneri ovaries indicates an annual reproductive cycle (Figure 17). Mature ovaries were observed in 44% of females examined in May and increased to 65% during August. Additionally, the percentage of advanced stage ovaries decreased from 34% in May to 8% in August concurrent with the increase in mature stages. Incidence of spent/redeveloping ovaries, first observed in August, coincided with the initial appearance of ovigerous females. Early and intermediate ovarian stages recorded during December comprised 35 and 36% respectively of the animals examined, while intermediate (15%) and advanced (30%) stage ovaries increased in abundance during February. Stages of ovarian development from animals collected at depths of 311 and 494 m were comparable throughout the sample period. Females from 677 m exhibited greater variation in ovarian stages than those from shallower depths. Variation in ovarian stages was also visible in females that did not undergo oviposition during the breeding period when reproductively active females brooded eggs. Oviposition of fenneri began in August with nine percent of all females collected bearing eggs (Figure 18) Ovigerous females were only collected from depths of 494 m during this period. However, as previously mentioned,

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72 310M w (.) D SPENT z w 491M a: a: MATURE ::l (.) I2J ADVANCED (.) 50 0 125 INTERMEDIATE z w (.) 0 EARLY a: w 100 ll. 673M 75 50 25 MAY AUG DEC FEB Figure 17. Quarterly ovarian stages of Chaceon fenneri by depth of sample. Key to ovarian stages is shown in the figure. All depths are in meters.

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Figure 18. Quarterly size frequency distributions of female Chaceon fenneri by depth of sample. N represents the number o f individuals and CW represents mean carapace width. All depths are in meters.

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73

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w 0 30 20 10 30 15 20 a: a: :> 10 0 0 0 .... z 30 a: w D.. 20 10 30 20 10 311 m MAY 1987 N= 227 cw = 126 AUG N = 253 cw = 127 DEC N = 95 cw = 126 FEB 1988 N = 141 cw = 127 110 110 100 110 120 130 140 150 1110 30 20 10 30 20 10 30 20 10 30 20 10 494 m MAY 1987 N= 269 cw = 121 AUG N = 204 cw = 122 DEC N= 94 cw = 121 FEB 1988 N= 118 CW=120 80 110 100 110 120 130 140 150 1110 CARAPACE WIDTH (mm) 40 30 20 10 40 30 20 10 40 30 20 10 40 30 20 10 677 m MAY 1887 N=7 cw = 112 AUG N=7 CW=116 DEC N= 20 CW=11a FEB 1988 N=3 CW=138 80 110 100 110 120 130 140 150 1110 OVIGEROUS 0 EGG REMNANTS

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75 ovaries from the majority of females examined were in the mature stage subsequent to the onset of oviposition. sixtyseven percent of females examined in December were ovigerous, the majority at 311 and 494 m. Only one percent of all ovigerous females were collected at 677 m. Eggs examined during this period were in developmental stage B (early segmentation of body) through C+ (eye visible, body segmentation pronounced) (see Meredith, 1952). Size range of ovigerous females examined was between 96 and 142 mm cw. Larval hatching of g. fenneri began in February. Twenty-six percent of females collected had egg remnants on the pleopods while 31% were ovigerous (Figure 18). Fully developed larvae were present in eggs examined during this period. Larvae were also observed hatching from egg bearing females held onboard ship in a refrigerated seawater system (T = 9. 5 C) Analysis of mean oocyte diameters provides further evidence of the annual reproductive cycle exhibited by this species. seasonal mean oocyte diameters of g. fenneri by sample depth are shown in Figure 19. Beginning in May, mean oocyte diameter increased through the summer months and reached a maximum in August prior to the onset of oviposition. Mean diameters from December and February showed a gradual increase in size as ovarian development proceeded toward the onset of the next period of oviposition. t d' meters from depths Seasonal changes mean oocy e 1a

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eo 3 10M (fJ z 0 a: (...) 491 M -a: LU 1-LU 300 < Cl 200 LU 1-100 >-(...) 0 0 673M z 500 < LU 300 200 100 MAY AUG DEC FEB 1987 1988 MONTH OF SAMP L E Figure 19 Quarterly mean oocyte diameter of Chaceon fenneri by depth of sample including standard deviation and oocyte diameter range. Depths are meters. 76

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77 of 311 and 494 m were similar except for samples from 494 m during August. However, samples from this depth included spent ovaries from a small percentage of females that had undergone oviposition somewhat earlier than those from 311 m. Mean oocyte diameters from females collected from 677 m showed less seasonality than those collected at shallower depths. Non-brooding females out of synchrony with the reproductively active members of the population showed greatest variation in mean oocyte diameters. Chaceon guinquedens Ovaries examined in 91 guinguedens also suggest an annual reproductive cycle. However, the cycle appears more protracted than that of fenneri. Mature ovaries were observed in 25% of females examined in May and in 30% of those examined in August. Spent/redeveloping ovaries comprised 35 and 30% respectively of females examined during those periods (Figure 20). Although the D ecember sample size was small, the majority of ovaries were in the intermediate or advanced stage. similarly, during February, intermediate and advanced ovaries predominated, with 15% entering the mature stage. As with fenneri, the presence of spent/redeveloping ovaries in guinquedens co-occurred with the first recorded incidence of ovigerous females. Ovigerous guinguedens wit h early stage eggs w ere first recorded during May (Figure 21), an indication that

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w (.) 100 z w a: 75 a: (.) (.) 50 0 25 w (.) a: MAY AUG DEC FEB lli] SPENT -MATURE 78 f2l ADVANCED INTERMEDIATE 0 EARLY Figur e 20. Quarterly ovarian stages of Chaceon quinquedens collected from 677 meters. Key to ovarian stages is shown in the figure.

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oviposition occurs temporally earlier in this species than in Q. fenneri. Twenty-six percent of females collected during May were ovigerous as were 26% of those examined in August. 79 Larval hatching of Q. quinquedens also occurred during February with 32% of females collected having egg remnants on the pleopods (Figure 21). No ovigerous females were collected during this period. Overall, carapace widths of ovigerous females were between 103 and 141 mm. Seasonal changes in mean oocyte diameters of Q. guinquedens (Figure 22) were less pronounced that those of Q. fenneri. Mean diameters and ranges quinquedens were greatest in May coinciding with the observed period of oviposition. Mean diameters from August were slightly less than May, although the size range of oocytes were comparable. During December and February, mean oocyte diameters began to increase as ovarian redevelopment proceeded; however, the increase in mean size during February was less pronounced than that of fenneri. Nonbrooding females showed greatest variation in mean oocyte diameters throughout the breeding period. Fecundity d't n carapace width for Regress1on analys1s of fecun 1 Y o 22 Q. fenneri and For each species, 11 Q. quinquedens is shown in Table 5. the number of eggs per brood was found to

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80

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Figure 21. Quarterly size frequency distributions of female Chaceon quinquedens collected from 677 meters in Areas 1 and 2.

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30 20 10 30 UJ 20 0 z UJ 10 J 0 0 0 t-30 z UJ 0 20 UJ A. 10 30 20 10 80 UAY 1987 N = 192 CW= 119 AUG 1987 N =153 CW=121 DEC 1967 N= 20 CW=125 FEB 1966 N=92 CW=125 30 20 10 30 20 10 60 30 20 10 30 20 10 60 ao CARAPACE WIDTH (mm) UAY 1987 N=77 CW= 114 AUG 1987 N =88 CW=116 DEC 1987 N=3 CW= 126 FEB 1988 N= 98 CW=118 100 110 120 130 140 150 180 OVIGEROUS 0 EGG REMNANTS (X) ......

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a: 600 w tw 500 4oo Oz 300 >-5 200 0'-' 0 100 --1-1-T r-1-...... t-,-I-f-1 I I I z < w MAY AUG DEC FEB 1987 1988 MONTH OF SAMPLE Figure 22. Quarterly mean oocyte diameters of Chaceon quinquedens collected from 677 meters, includ1ng standard deviation and oocyte diameter range. 82

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83 Table 5. Summary of regression analysis of fecundity for Chaceon fenneri and Q. quinguedens. N equals the number of individuals examined and cw equals carapace width in mm. Both linear regression equations are significant at P<0.05. N Mean CW (mm) CW range Mean egg number Range Fecundity = b{CW)+c AN OVA Q. fenneri 22 121 (104-140) 250622 (114000-435000) Y = 6741(CW)-561039 0.66 F(1,20) = 38.15 Q. quinguedens 11 124 (113-136) 227160 (156000-289000) Y = 4271(CW)-303216 0.68 F{1,9) = 19.05

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increase significantly with increasing carapace width. Comparison of fecundity between species showed no significant differences in the numbers of eggs per brood over the size range of females examined (ANCOVA F = 1.535; P
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85 individuals that showed signs of molting activity, 30% of all intermolt females did not carry eggs during December. This may be considered the height of the brooding season, as 70% of all intermolt females carried late stage eggs during this period. A similar trend was visible during February when brooding females either had late stage eggs prior to larval hatching or egg remnants in the pleopods. During this period, 42% of all intermolt females showed no signs of recent reproductive activity. The portion of the population that is either molting or not producing eggs during the breeding period are out of synchrony with egg bearing females and cannot be considered part of the reproductively active population. Molting of guinguedens was even less pronounced than that of fenneri. Fewer than two percent of all female guinguedens were found to show signs of recent molting (CW range 105-133 mm). The majority of crabs examined were in the intermolt stage and showed varying degrees of carapace discoloration and fouling by the pedunculate barnacle Poecilasma sp. As with fenneri, this species also undergoes molting prior to mating (Elner et al, 1987) A similar trend of intermolt females not carrying eggs during the observed brooding season was also visible in guinguedens. Although molting females were not as frequent, fewer than 30% of all intermolt females were observed to carry eggs during the nine month brooding season. brooding intermolt females As with fenner1, non-

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86 appear to be out of synchrony with the reproductively active portion of the population. Discussion Comparative Reproduction The annual reproductive cycle of fenneri from the eastern Gulf of Mexico corresponds to that observed in females collected from southeast Florida (Chapter 4). Incidence of ovigerous females, seasonal changes in the visual condition of the ovaries and in mean oocyte diameters, and the incidence of egg remnants are similar between females from each geographic area. Wenner et al (1987) suggested a restricted spawning season for this species from the South Atlantic Bight, but the low abundance of females collected during that study prohibited a thorough analysis of the reproduction cycle; no comparison is possible with the present data. No depth-related differences were noted in the temporal sequence of reproductive events (ie oviposition, egg development rates and larval hatching) of fenneri. The few females collected from 677 m showed greater variation in ovarian stages and mean oocyte diameters than animals from shallower depths. only one ovigerous female was collected from 677 m. This suggests that these individuals were not in synchrony with females from shallow depths and that

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87 environmental cues that synchronize the reproductive cycle may be dampened with depth. However, the small sample size of 37 individuals does not allow firm conclusions to be drawn. Wigley et al (1975) reported depth related differences in the developmental stages of guinguedens eggs and suggested that reproductive events are of shorter duration at upper slope depths. Oviposition would occur earlier at greater depths and egg maturation would be prolonged due to lower temperatures. Haefner (1978) observed seasonal differences in egg developmental stages of guinguedens; no differences were noted with depth. Seasonal differences would be expected in a continuously reproducing species as oviposition would show temporal variation (Giese, 1959). However, if environmental triggers are indeed dampened with depth, temporal differences in reproductive events as shown by female Q. fenneri collected from 677 m would be expected. Although sample depths were limited, the reproductive cycle of Q. guinguedens observed in the present study approximates the protracted annual cycle proposed by Ganz and Hermann (1975). These authors suggest that oviposition occurs in July and August with eggs carried for nine months until hatching in May. In contrast, Haefner (1977, 1978} reported the presence of ovigerous females year round and suggested a continuous reproductive cycle. Seasonal differences in ovarian development and egg developmental stages indicated a prolonged period of oviposition between

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88 June and November. Eggs were presumed to hatch between January and June with egg maturation complete in approximately seven months. Unfortunately, the latter study encompassed seasonal data collected asynchronously over a period of four years; assessment of a continuous reproductive cycle may have been complicated by this sampling pattern. The major difference between the reproductive cycles of Q. fenneri and Q. guinguedens noted in the present study was in the timing of oviposition and duration of egg development. Oviposition in Q. guinguedens was observed between May and August, approximately three months earlier than Q. fenneri. Both species' larvae hatched in February, thus egg maturation was complete in approximately six months in Q. fenneri and nine months in Q. guinguedens. Variation in egg development times probably reflects the different bathymetric and geographic distributions of the two species. The upper slope distribution of Q. fenneri throughout the southeastern United States subjects brooding adults to warm temperatures that would enhance egg maturation rates (Wear, 1974). Conversely, the colder temperatures characteristic of the upper slope off the New England states and canadian Maritime provinces may be responsible for the protracted development of eggs of Q. guinguedens. This probably applies as well to Q. quinquedens which have undergone isothermal submergence to inhabit deep slope depths in the southern portion of its

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89 extensive geographic range. Fecundity Fecundity estimates for fenneri from the eastern Gulf of Mexico are comparable with those of females from southeast Florida (Chapter 4). over the size range examined, larger females had a significantly greater brood size than smaller crabs. A similar relationship is observed in brood sizes of quinquedens (this study; Hines, 1982) and has also been reported for maritae (Melville-Smith, 1987c) A trend of size-dependent fecundity is common among brachyurans and is directly related to the volume of the cephalothorax available for yolk accumulation (Hines, 1982). Egg diameters for fenneri range between 580-610 those of guinguedens are slightly larger and measure between 630-850 (this study; Gray, 1969; Hines, 1982, 1988). These egg sizes are among the largest known for brachyurans with planktotrophic development. Body size is a major determinant of brachyuran reproductive output, but egg size is the factor that accounts for variation in fecundity between equivalent size crabs (Hines, 1982). Although not apparent in this study, inter-specific comparison of brood size between similar sized animals indicates that fenneri produces a greater number of smaller eggs, while quinquedens produces fewer, larger eggs (Hines, 1988). This suggests that although fenneri reaches a greater

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90 maximum size than quinquedens, s 1'ze --__ spec1fic fecundity may be equal between each species. The large eggs of fenneri and quinquedens may provide nutritional flexibility to larvae that migrate from depths greater than 300 m to the surface to complete development (Roskowski, 1979; Sulkin and van Heukelem, 1981). Chaceon fenneri shows a subtropical and tropical distribution; overlying waters may provide a more stable, low level source of food than temperate regions. Thus, the smaller egg size of fenneri may reflect a reduced parental investment per egg that is offset by a larger brood size. Conversely, the larger eggs and reduced brood size of quinguedens may reflect the distribution of this species in less stable temperate and boreal waters. This larger egg size may also provide some selective advantage for quinquedens larvae that would migrate a greater vertical distance than those of fenneri in the bathymetrically segregated populations of the eastern Gulf of Mexico. Differences in adult habitat temperatures may also be responsible for different egg maturation rates shown by each species. Wear (1974) has shown that over a normal range of habitat temperatures, reduced temperatures increase egg development time in shallow water temperate d ecapods. This is particularly apparent in species that produce multiple broods during one breeding season. Therefore, the distinct bathymetric and geographic distribution patterns of fenneri and guinguedens may subject brooding females

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91 to different suites of environmental temperatures that may affect egg maturation rates. However, among closely related species, larger eggs show a longer maturation period at equivalent temperatures (Wear, 1974: Steele and steele, 1975). Thus, the longer development time for eggs of Q. quinguedens may also reflect the larger eggs of this species. Although differences in egg sizes and adult habitat temperatures may affect egg maturation rates, Clark (1982) has suggested that the large eggs and slow development times characteristic of cold water invertebrates are K-strategy tactics adapted to patterns of seasonal food availability. Peak periods of larval hatching coincide with the onset of optimum conditions for survival. The spring hatch of Q. fenneri and Q. guinguedens larvae would coincide with the increases in temperature and productivity in overlying waters which would enhance larval survival. During early spring, larvae migrating to surface waters encounter warm temperatures that increase rates of development. Larvae of Q. guinguedens reared at a characteristic spring surface water temperature of 22 c showed rapid metamorphosis to megalopa within 22-30 days. Conversely, larvae reared at adult habitat temperatures of less than 12 c averaged 120 days to metamorphosis (Roskowski, 1979). Differences in survival and growth rates t 1 temperatures also over the range of Roskowsk11S exper1men a . t s as development suggested a shift 1n opt1mal tempera ure

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proceeded. Early stage larvae tolerate cool temperatures, but the zone of thermal tolerance decreases in range and shifts to warmer temperatures as development proceeds. Regardless of the mechanisms involved, this can be considered an adaptation in deep-sea species with planktotrophic larvae that show extensive vertical migration. In addition to effects of surface temperatures, the onset of increased productivity in the upper 200 m would presumably provide a greater variety of potential food items. Sulkin and van Heukelem (1981) have shown that guinguedens larvae exhibit greater dietary flexibility 92 than shallow water brachyuran larvae. This has been suggested as an adaptive mechanism for deep-sea species with vertically migrating planktotrophic larvae. Dietary flexibility would presumably offset the energy cost associated with extensive vertical migration. Life History strategies The additional data on reproduction and molting of fenneri provide greater support for the annual population level -biennial individual level reproduction cycle The Cycle 1'ncludes alternate years proposed in Chapter 4. of growth and reproduction and is modeled in Figure 23 rings in the figure represent the temporal sequence of molting and egg brooding of two individuals within the The

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JANUARY YEAR 1 JULY JULY JANUARY YEAR 2 Figure 23. Biennial reproduction model proposed for Chaceon fenneri and. guinguedens. The rings represent the temporal sequeuce of molting and egg brooding of two individuals within the population during a two year period. 93

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population over a two year period. In January of Year 1, the female represented in the inner ring would be brooding eggs prior to larval hatching which occurs during February and March. Subsequently, this female would molt and mate during the fall and winter months of Year 1 and oviposit eggs during late summer of Year 2. 94 In contrast, the female represented by the outer ring would have recently molted and mated at the beginning of Year 1 and would oviposit eggs during late summer of this year. Eggs would be brooded until hatching in February and March of Year 2. Molting and mating would occur during the fall months of Year 2. Thus, reproduction would occur annually on the population level, but biennially on the individual level. The low frequency of molting females and the incidence of non-ovigerous intermolt stage females observed during the breeding season suggests that potential energy restraints have led to the evolution of a low frequency of reproduction in fenneri. It is also suggested that this LFR pattern may also apply to the congener Q. guinguedens as well. In the Gulf of Mexico, this species shows the protracted annual cycle suggested by Ganz and Hermann (1975). As with fenneri, the low numbers of molting females and high incidence of intermolt females without eggs during the b h t 1 growth and alternate reeding season suggests t a s ow be present in this years of reproductive act1v1ty may species as well.

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95 This reproduction pattern may be a major adaptation to the reduced food supply characteristic of the continental slope and its potential effect on growth and reproduction. The evolution of a low frequency of reproduction and robust planktotrophic larvae may be major adaptations that contribute to the success of these species on the continental slope. Life history tactics of the Geryonidae appear to include aspects of the bet-hedging strategy proposed by Stearns (1976). Geryonids exhibit slow adult growth, late maturity, delayed and iteroparous reproduction, large eggs and reduced fecundity. Environmental conditions may contribute to variable larval and juvenile mortality, however, once adult size is reached, mortality is probably low. Utilization of the LFR pattern may actually increase adult survival; alternate years of molting would reduce molt associated risks while biennial reproduction would increase the period for accumulation of sufficient energy reserves to reproduce. It may also serve to ensure reproductive success when mates are difficult to find. Additional adaptations shown by larvae include a peak period of hatching coincidental with optimum conditions for survival, flexible nutritional requirements and the ability to survive and grow over a wide range of temperatures. Although knowledge of broad scale larval distribution patterns, and the settlement and distribution of juveniles are non-existent, our present knowledge of the reproductive patterns of these slope

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96 dwelling species suggests the successful modification of characteristic shallow water brachyuran reproductive tactics that have led to successful colonization of the continental slope habitat.

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CHAPTER 6. COMPARATIVE BATHYMETRIC AND GEOGRAPHIC DISTRIBUTION OF CHACEON FENNER! AND QUINQUEDENS IN THE EASTERN GULF OF MEXICO Introduction 97 A distribution pattern of larger size with increased depth has been reported for some groups of continental slope megafauna (Polloni et al, 1979). This is in contrast to the smaller-deeper pattern shown by slope macrofauna and meiofauna (Thiel, 1975; 1979). The patterns observed have been proposed to reflect depth dependent changes in energy sources available to each trophic level (Haedrich and Rowe, 1977). Besides cropping the predominantly deposit feeding macrofauna and meiofauna (Dayton and Hessler, 1972), megafauna may also depend on temporally and spatially unpredictable deadfalls (Rowe and Staresinic, 1979; Jumars and Gallagher, 1982). Pelagic organisms that come in close proximity to the substrate may also provide significant food items (Haedrich and Rowe, 1977; Somera, 1982). Thus, where mobility can aid in the location of unpredictable food sources, large size may be an advantage. Conversely, s maller size would aid deposit feeding macrofauna and meiofauna that inhabit fine grain sediments

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and feed on a thin layer of organic material (Haedrich and Rowe, 1977; Polloni et al, 1979). 98 Geryon crabs do not show the typical bigger-deeper distribution pattern shown by other slope megafauna. Juveniles and smaller individuals show greatest abundance at depths exceeding 750 m, while larger individuals predominate in shallower depths (Manning and Holthuis, 1981, 1989). This may be due to an upslope migration by older individuals, particularly reproductively active females which show greatest abundance at upper slope depths of 200 to 450 m (Wigley et al, 1975; Beyers and Wilke, 1980; Melville-Smith, 1987c; Lockhart, 1988). The environment typical of upper slope depths provides conditions more conducive to larval survival in addition to providing more adult food items. Males show a smaller-deeper distribution but do not inhabit depths as shallow as females. The partial segregation by sex and decrease in size with depth is common among the Geryonidae (Manning and Holthuis, 1989). However, the specific distribution patterns of many Geryonidae remain unknown, especially in areas where congeneric species overlap in their respective ranges. Materials and Methods Intra-specific differences in the bathymetric and geographic distributions of female g. fenneri and guinguedens were examined as part of the sampling program

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99 Presented in the previous chapter. F h b or eac era carapace width and length were measured to the nearest rnm and sex of each individual recorded. Multi-factor analyses of variance (ANOVA) were used to test the effects of area, season and depth on mean size of each species. A more thorough analysis of broad scale abundance, and geographic and bathymetric distribution patterns were examined as part of a companion study (Lockhart et al, in press); only female crabs will be considered here. All computations were made on an IBM Model 50 personal computer using the Statgraphics statistical analysis package. Bottom temperature was recorded at each sample site throughout the study period with reversing thermometers and expendable bathythermographs (XBT). Surface sediment samples were collected with a modified Capetown dredge and analyzed for qualitative composition and grain size. Results Physical Conditions Seasonal mean temperature ranges were 11.0-12.4 c at 311m, 8.3-9.8 cat 494 m and 6.4-7.6 cat 677 m (Table 6). . temperature was most pronounced Seasonal var1at1on 1n t depths showed little at 311 m; temperatures at grea er variation throughout the sampling period. Pr1'mar1'ly foraminiferal ooze (G. otvos, Sediments were

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100 Table 6. Bottom water temperature ( C) by area, season and depth including; annual mean temperature by area and depth, and seasonal mean temperature by month and depth. Area Depth Cml May Aug Dec Feb Mean 1 311 11.7 11.0 12.4 12.5 11.9 494 8.1 8.4 8.6 8.0 8.3 677 7.3 6.5 6.5 6.5 6.7 2 311 10.5 12.7 12.1 10.8 11.5 494 8.3 8.6 9.8 8.8 8.9 677 9.0 6.3 6.2 6.3 6.7 3 311 11.4 11.5 12.3 10.9 11.5 494 9.4 8.3 12.2 7.7 9.4 677 7.4 6.4 8.0 6.7 7.1 4 311 10.4 11.6 13.5 10.7 11.6 494 9.2 7.7 9.3 8.4 8.7 677 6.9 6.6 9.4 6.7 7.2 5 311 11.1 12.5 11.6 10.8 11.5 494 8.2 8.6 9.0 8.6 8.6 677 7.5 6.4 6.8 6.6 6.8 Seasonal 310 11.0 11.9 12.4 11.1 mean of 8.3 9.8 8.3 all 494 8.6 areas 6.4 7.4 6.6 677 7.6

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101 Gulf Coast Research Laboratory, pers. comm.). Silt and clay size sediments dominated all depth strata in Areas 1 2 and 3. Sediments from Area 4 were sand and silt at depths of 311 and 494 m; silt and clay dominated at 677 m. Area 5 to the south showed coral rock and rubble at 311 m and sand dominated sediments at 494 and 677 m. Distribution Patterns A total of 1438 female fenneri and 765 female guinguedens were collected throughout the study period. Both species showed different bathymetric and geographic distributions in the northeastern Gulf of Mexico. Female fenneri were only recorded at Areas 4 and 5, the southernmost stations. Chaceon guinguedens was more common (95% of total) at Areas 1 and 2 in the north. No fenneri and only three guinguedens were collected from Area 3 adjacent to DeSoto canyon. Each species also showed different patterns of bathymetric distribution. Chaceon guinguedens was restricted to sample depths of 677 m, while fenneri was most abundant at upper slope depths of 311 and 494 m. Females from 677 m comprised only 2.5% (N = 37) of all fenneri caught. Data from 677 m was not sufficient for inclusion in statistical analyses. Results of analyses on effects of area, season and depth on size fenneri are shown in Table 7 There was

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102 no significant effect of area or season on mean size of female (p<0.05), therefore, data from Areas 4 and 5 were pooled to examine the effect of depth on size (Figure 18; the seasonal size frequency distributions shown were used in analysis of reproductive patterns}. Mean carapace width (CW) was greatest at 311 m regardless of season and decreased with increased depth. Results of a follow up ANOVA indicated significant depth related differences in mean size of females from 311 and 494 m (Table 7). Although data from 677 m was insufficient for analysis, mean size of females was usually smallest at that depth. Female Q. guinguedens were present only at 677 m and were more abundant in the northern portion of the study area. Only 39 individuals were collected from Areas 3, 4, and 5. Except for the December sample period, female Q. guinguedens from Area 1 were consistently larger than those from Area 2 regardless of season (Figure 21). However, differences in mean size recorded during December may reflect the reduced abundance of females collected during that period.

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Table 7. Results of statistical analyses on effects of area, season and depth on mean carapace width of female Chaceon fenneri. DF equal degrees of freedom. source of variation DF F ratio Area 1 0.133 Season 3 0.443 Depth 1 125.906 Foll ow up one way ANOVA: effect of depth Depth 1 131.451 * S ignificant at p<0.05 103

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104 Discussion Bathymetric Distribution The presence of larger female fenneri at upper slope depths is similar to the size-depth patterns reported for Q. maritae (Dias and Machado, 1973; Intes and Le Loueff, 1976; Beyers and Wilke, 1980) guinguedens (Wigley et al, 1975; Haefner, 1978; McElman and Elner, 1982). Throughout the eastern Gulf of Mexico, male fenneri are partially segregated from females and are more abundant at depths of 450 to 600 m (Lockhart, 1988; Lockhart et al, in press) Partial overlap between sexes occurs at depths between 394 and 450 m; few females are found below 450 m. Similar patterns of segregation by sex with depth have also been reported for Q. maritae from southwest Africa (Dias and Machado, 1973; Intes and Le Loueff, 1976; Beyers and Wilke, 1980) and for Q. guinguedens from the northeast coast of North America (Wigley et al, 1975; Haefner, 1978; McElman and Elner, 1982). The great abundance of large female fenneri (ovigerous and non-ovigerous) recorded from upper slope depths suggests an upslope movement of reproductively active females. Melville-Smith (1987a, 1987b) noted that mature female c. maritae showed greater movement patterns than immature females and males. This was suggested as greater 't ble forage activity by females in search of more SU1 a

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105 habitats. An up-slope movement into areas of increased biomass (Rowe et al, 1974) increases diversity of potential food items. It also subjects brooding females to warmer temperatures which may enhance the rate of egg development (Wear, 1974). Upslope movement would also lessen the distance for larvae to migrate to surface waters and reduce the potential energy cost associated with that migration. The segregated bathymetric distribution shown fenneri and guinguedens in the eastern Gulf of Mexico may indicate potential differences in substrate requirements between species. In this area, fenneri shows greatest abundance on coarse grain sediments and rock outcroppings (Lockhart, 1988; this study) but is absent on silty-clay sediments at equivalent depths (Otwell et al, 1984; Lockhart, 1988; this study). The species was also recorded from sandy sediments in the mid-Atlantic bight but was conspicuously absent from coral rocks and rubble (Wenner et al, 1987). Conversely, quinquedens is usually found on soft silty-clay sediments off northeastern North America (Wigley et al, 1975; McElman and Elner, 1982); this was also true in the eastern Gulf of Mexico. Differences in dactyl morphologies of the walking legs of fenneri and quinquedens may reflect adaptations to the substrates that each species inhabits (R.B. Manning, Smithsonian Institution, pers. comm.). The dactyls of 11 Compressed and more suitable for fenneri are latera Y hard substrates. Those of quinquedens are dorso-

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ventrally compressed: a suggested adaptation for greater mobility on soft silty substrates. Although it may be tempting to correlate the distribution of fenneri and guinguedens with a particular bottom type, distribution of sediments in the eastern Gulf of Mexico are due to surface circulation patterns. Sediments of the northern Gulf of Mexico continental slope are not sorted by currents and are predominately silts and clays (Ludwick, 1964: Doyle and Sparks, 1980). Conversely, between 200 and 600 m on the west Florida slope, sandy sediments and rock outcroppings 106 are common due to the winnowing effect of the Loop Current (Mullins et al, 1988). Slope sediments from depths in excess of 600 m are not affected by the Loop current and are primarily west Florida lime-mud (Blake and Doyle, 1983: Mullins et al, 1988). This same pattern of coarse grain sediments and rock outcroppings can be found associated with Gulf Stream activity as far north as Cape Hatteras (Rowe and Menzies, 1969: Doyle et al, 1979). As off west Florida, silty-clay sediments are found on the slope at depths below Gulf Stream influence. North of Cape Hatteras, soft siltyclay sediments dominate on the slope due to the absence of boundary current winnowing, although rock outcroppings are present due to mass wasting phenomena (Doyle et al, 197 9 ) Although there may be a substrate preference in fenneri and guinguedens, temperature may also play a major role in determining the bathymetric distribution of

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107 these species on the continental slope. The upper slope distribution of fenneri in temperatures between 8 and 12 c suggests that this species is adapted to warmer temperatures. Conversely, the isothermal submergence shown by guinguedens indicates that this species may be limited by temperatures above 8 c. Although Q. guinguedens has occasionally been reported from temperatures greater than 8 c, abundance is usually low (Wigley et al, 1975; Haefner, 1978; McElman and Elner, 1982). The species shows signs of physiological stress when exposed to temperatures in excess of 9.5 c (Gray, 1969; Ganz and Hermann, 1974). Soto (1985) suggested that the 10 c isotherm may limit the upper slope distribution of both species. If this is valid, one would expect to find Q. guinguedens at 491 m throughout the eastern Gulf of Mexico. Chaceon fenneri would not be as abundant at 310 m where temperatures exceed 10 c. Chaceon fenneri would also not be present off southeast Florida at depths of 210-230 m (Chapter 4). Although both species appear to be cold stenotherms, the upper slope distribution of Q. fenneri appears to be restricted by the 12 c isotherm, while the 8 c isotherm may delineate the minimum depth distribution of guinguedens.

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108 Geographic Distribution Although temperatures were similar by area, season and depth, the absence of fenneri from the northern Gulf of Mexico suggests a casual relationship between larval distribution and prevailing current patterns. surface circulation in the eastern Gulf of Mexico is dominated by the anti-cyclonic flow of the Loop Current (Hoffman and Worley, 1986). Northward penetration of the Loop current varies seasonally and annually (Maul, 1974), but the downstream portion is usually associated with the west Florida continental margin. The effective depth of Loop current circulation is in the upper 500 m (Hoffman and 1986) which corresponds to the bathymetric range of fenneri on the slope. During early spring, newly hatched larvae that migrate to the surface would be entrained in the downstream portion of the Loop Current and transported south through the Straits of Florida and into the Gulf stream system. Although larval development times vary with temperature (Roskowski, 1979), dispersal of new individuals would generally follow the Loop-Florida-Gulf stream current system which may account for the "western boundary distribution" of this species. As the proximity of the Loop current to the shelf-slope break varie s seasonally and annually (Hoffm a n and Worley, 1 986), larvae not entrained may be dispersed locally on the slope (Kelley et al, 1982). This would reduce unidirectional

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109 dispersal and gene flow. Unfortunately, little is known of larval dispersal or juvenile settlement of most Geryonidae. Additional populations of Q. fenneri may also exist off Yucatan Peninsula, where the Loop current enters the Gulf of Mexico. However, there are no records of that species from Central America. Larvae of Q. guinguedens from the northern Gulf of Mexico would not be affected by Loop Current circulation except in years of unusual penetration to the north. Consequently, larval dispersal may be quite localized and only affected by coastal water movement. This dispersal pattern would account for the greater abundance of Q. guinguedens in the northern Gulf of Mexico. Larvae hatched off west Florida would be subject to dispersal to the south via the Loop Current. This may account for the reduced abundance of that species in the eastern Gulf of Mexico. However, sample depths were limited and the distribution of that species at depths greater than 677 m remains unknown. Although generalized patterns of the bathymetric distribution of guinguedens and Q. fenneri have been established for the eastern Gulf of Mexico, information on these species from the western gulf is non-existent. Data is also absent on the larval dispersal and recruitment of juveniles of each species.

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CHAPTER 7. OXYGEN CONSUMPTION OF CHACEON FENNER! AND QUINQUEDENS Introduction 110 Physiological rates of deep-sea organisms show a decline with increased depth. This has been demonstrated for bacteria (Jannasch and Wirsen, 1973), infaunal communities (Smith and Teal, 1973), benthopelagic fishes (Smith and Hessler, 1974), and meso-and bathypelagic fishes (Smith, 1978; Torres et al, 1979; Childress et al, 1980) and crustaceans (Childress, 1975). Data on metabolic rates of slope dwelling megafauna, particularly invertebrates, are not available. The decline in metabolic rates has been attributed to the decrease in biomass characteristic of increased depth (Rowe et al, 1974; Rowe, 1983). Reduced biomass may have a significant effect on the metabolic rates of members of higher trophic levels, particularly highly motile benthic megafauna that depend on random deadfalls as a significant food source (Rowe and staresinic, 1979) Temperature dependent differences in metabolic rates have also been reported for deep-living pelagic fishes and crustaceans as a function of depth of occurrence (Donnelly

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111 and Torres, 1988). Geographical differences in depth related temperature regimes have been shown to influence the depth distributions among congeneric species (Childress, 1975; Torres et al, 1979; Donnelly and Torres, 1988). Therefore, both temperature and food supply have a significant influence on the physiological processes of deep-sea organisms. The segregated bathymetric distribution shown by fenneri and guinguedens within their common geographic range suggests potential differences in temperature tolerance between each species (Soto, 1985). The temperature and distribution data presented in Chapter 6 formulated the hypothesis that the 12 c isotherm limits the upper slope distribution of fenneri, while the minimum depth distribution of guinguedens is limited by the 8 c isotherm. Therefore, if temperature is an important factor responsible for the segregated bathymetric distribution of these species, measurements of oxygen consumption rates over the range of habitat temperatures should show interspecific differences in metabolism. Materials and Methods Specimens of fenneri and guinguedens were collected depths of 310 to 699 m in the eastern Gulf of from Mexico during 1988 (refer to chapter 5 for sample February, site location and collection methods) Bottom water

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112 temperatures were recorded at each sample depth using reversing thermometers and XBTs (Table 6). 11 A an1mals were held aboard ship in a refrigerated recirculating seawater system (T = 9.5 c) for transport purposes. In the laboratory, crabs were kept in two refrigerated aquarium systems maintained at 9 c ( 0.5 "C) and 35.0 ppt.; lighting was reduced to near darkness. All crabs were fed scallop meats, shrimp, and squid. Temperatures were raised or lowered to selected experimental temperatures over periods of 12-14 days. Once experimental temperatures were achieved, crabs were acclimated for 14 days prior to measurement of respiration rates (V02). Experimental animals were isolated from other animals and starved for 1012 days prior to each experiment. Oxygen consumption rates were d etermine d by allowing individual crabs to deplete the oxygen in a sealed, seawater filled Plexiglass chamber. Chamber volume was 22.0 liters. Experimental temperatures of 6 and 12 c ( 0.2 c) were maintained in the chamber by circulation o f refrigerated water through a surrounding water jacket. The entire chamber was insulated with 2.5 em thick styrofoam to reduce temperature fluctuations during each experimental period. The chamber was then covered with black plastic to reduce light to minimum levels. Three crabs of each species were tested at each experimental temperature. All experimental ht to preclude size animals were of equivalent size and w e1 g related variations in oxygen consumption rates.

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113 Seawater used in each experiment was a 50-50 mix of Gulf of Mexico seawater and Instant ocean aquarium salt, adjusted to 35.0 ppt. The seawater was vacuum filtered through a 0.47 glass fiber filter and stored at experimental temperatures. Streptomycin and Neomycin (25 mg/1 each) were added to minimize microbial activity. To control for potential microbial oxygen consumption, the experimental animal was removed after selected runs, its volume replaced by fresh seawater, and the oxygen consumption measured for an additional 4-6 hours. Microbial respiration was negligible in all cases. Between each experiment, the chamber was washed and fresh seawater added. Partial pressure of oxygen was continuously measured with a Clark type polarographic oxygen electrode. To insure adequate circulation, a stirring bar was p laced in a 7.5 em diameter plexiglass cylinder attached upright to the bottom of the chamber. The cylinder was perforated with 2.5 em holes and partially enclosed the oxygen electrode; this served to protect the electrode from contact by experimental animals. The stirring bar was kept at minimum speed to prevent excessive turbulence within the chamber. Electrodes were calibrated for each experiment using air and nitrogen saturated seawater kept at experimental temperatures. the same animals were utilized at each experimental As term1nated when oxygen partial temperature, experiments were pressures approached 20-25 mm Hg. Experimental run times ranged from 16-20 hours at 12 c, and 24-29 hours at 6 c.

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114 At the end of each experiment the crab was blotted dry, and the wet weight recorded to the nearest 0.1 g. Data were recorded on a potentiometric strip chart recorder. Each chart was then scaled for total run time and total oxygen concentration (ml 02/1). The change in oxygen concentration was then measured directly from the scaled strip chart using a Houston Instruments Complot large format digitizing table and recorded on a HP-90 microcomputer. To eliminate elevated rates due to handling during the initiation of each experimental run, data from the first 2-3 hours were not used in rate calculations. Respiration rates were measured between P02s of 110 and 30 mg Hg. Weight specific V02s were calculated in ml 02/g wet wt/hr. Activity levels of each animal were observed every 2-3 hours during each experiment. Although these species are relatively lethargic at habitat temperatures (personal observations from the Johnson sea-Link submersible), activity levels during experiments varied among individuals. Since this was not quantitatively measured, its effect on metabolic rates was impossible to assess. Therefore, the respiration rates reported here should be regarded as estimates of routine metabolism. Results At each experimental temperature, oxygen consumption rates of individual animals of each species remained fairly

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115 constant over the P02 range of 110-30 mm Hg. All experiments were terminated before Po2s fell below a critical pressure of 20 mm Hg (Handley et al, 1987) [Pc = that critical partial pressure where the oxygen consumption rate changes and declines rapidly. (Prosser, 1973)]. Mean respiration rates of Q. fenneri and Q. guinguedens as a function of temperature are shown in Table 8. vo2s of each species were approximately equal at each experimental temperature. Q10s for each species are also shown in Table 8; these values were also equivalent for each species over the 6 c range of experimental temperatures. Table 8. Routine respiration rates (V02 ) and Q10s of Chaceon fenneri and guinguedens acclimated and measured at 6 and 12 c. N represents the number of individuals tested at each temperature. vo2 is expressed as ml 02/gm/hr and weight is expressed in grams. Species T c fenneri 6 12 guinguedens 6 12 N 3 3 3 3 vo2 (range) Weight (range) 0.010 484 (0.009-0.012) (454-512) 0.014 488 (0.012-0.017) (450-507) 0.008 411 (0.008-0.010) (375-440) 0.012 400 (0.012-0.013) (362-438) Although not quantified, Q. fenneri showed greater 1. 82 1. 78 during experiments at 12 c. activity than guinguedens Chaceon fenneri was observed to move about the chamber and

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116 often hung on the perforated column used to protect the oxygen electrode. Chaceon guinguedens usually remained quiescent on the bottom of the chamber at this temperature. Both species showed greater activity levels at 6 c and were often observed hanging on the perforated column surrounding the oxygen electrode. Observations of activity levels were made on each species while in the refrigerated holding system. At 12 c, fenneri was quite active and often observed to climb on the artificial habitat present in the holding system. Conversely, guinguedens was usually quiescent and only became active in the presence of food. Both species were quite active at 6 c regardless of the presence of food. Discussion At each experimental temperature, the rate of oxygen consumption of individual Q. fenneri and Q. guinguedens remained nearly constant over the P02 range of 110-30 mm Hg. In crustaceans, this is usually achieved by increased ventilation volume and percent oxygen utilization (Wolvekamp and Waterman, 1960). Handley et al (1987} also reported a p as reached at 2 0 mm constant vo2 for fenneri unt1l a c w Hg. d 1'ncreases in The constant rate was mainta1ne v1a scaphognathite beat and branchial chamber pressure. These and Q. guinguedens are observations indicate that Q. fenner1 (vernberg and vernberg, 1972} and efficient oxy-regulators

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117 would be able to tolerate the lowest 1 evels of oxygen to be expected on the continental slope. The 01o values obtained for each species indicate that temperature is a major factor affecting the respiration rates of fenneri and guinguedens. The increase in rates over the 6 c temperature range approximate a Q10 of 2.0, which indicates no compensation for temperature in the oxygen consumption rates of these species (Vernberg and Vernberg, 1972; Prosser, 1973). However, the equal vo2s and Q10s also suggest that temperature may not be the primary factor that accounts for the segregated bathymetric distribution of these species as proposed in Chapter 6. Throughout the eastern Gulf of Mexico study area, the bathymetric distribution of each species displayed a strong correlation with temperature {Chapter 6). Chaceon guinguedens was restricted to depths of 694 m where temperatures never exceeded 8 c, while fenneri was present at shallower depths where temperatures were as high as 13.5 c. Thus, the previously proposed hypothesis that the minimum depth distribution of guinguedens is limited by the 8 c isotherm (Chapter 6) is not supported by the respiration data presented here. The similar VOzs of each species over the 6-12 c range examined indicates no interspecific differences due to temperature. Thus, 1 in the segregated temperature does not wholly exp a distribution of these species on the continental slope of the eastern Gulf of Mexico.

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118 The absence of temperature dependent differences in the respiration rates of fenneri and guinguedens does provide initial support for the alternative hypothesis of substrate differences influencing bathymetric distribution of these species (Chapter 6; Lockhart, 1988). Chaceon fenneri was primarily found on coarse substrate and hard bottoms present at depths of 310 and 494 m off peninsular west Florida. In contrast, guinguedens was recorded from the soft silty substrates present at 694 m in all sample areas. The absence of guinguedens on similar soft substrates at depths of 310 and 494 m in the northern Gulf of Mexico (Areas 1 and 2) appears temperature related. Temperatures at these depths exceeded 8 c and were similar at all sampling areas. The metabolic rates of other slope dwelling invertebrate megafauna, particularly crustaceans have not been examined. Thus, data for comparative purposes are unavailable. However, oxygen consumption rates have been reported for large shallow water cold temperate crustaceans (Table 9). The V02s of Cancer pagurus, magister, Maia sguinado, and Homarus americanus are comparable to those d c auedens at equivalent shown by Chaceon fenner1 an _. gu1n temperatures (Table 8). This similarity in oxygen consumption rates may be a reflection of the respective 'nhabits environments that each group of spec1es 1 similar between each Although habitat temperatures are d t' pressure and food group, other factors such as pre a 10n

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119 Table 9. Comparative routine respiration rates for large cold temperate shallow water crustaceans. vo is expressed as ml 02/gm/hr and weight in grams. Value beJeath vo represents acclimation and experimental temperature fn c. Species Source Weight Range vo2 vo2 vo2 T c 6 12 Cancer pagurus A 363-753 0.010 0.008 0.011 (10) cancer magister B 343-1073 0.013 0.012 0.018 (7.5) Maia sguinado A 510-679 0.010 0.008 0.011 (10) Homarus americanus C 380-520 0.021 0.014 0.021 (12) rate shown derived from cited sources using a Q\0 of 2.0. Original rate and experimental temperature from c1ted source is shown in column 3. A: Aldrich, 1975a, 1975b B: Prentice and Schneider, 1979 C: McLeese, 1964

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120 availability would be quite different h 11 1n s a ow water and deep-sea environments (Hochachka and Somera, 1984). activity at a higher metabolic cost (Brett and Groves, 1979). However, this high cost would be offset by the greater availability of potential food items in shallow water environments. In the food poor environment of the deep sea, many animals employ a float and wait feeding strategy, which reduces the energetic cost of locomotion to extremely low levels (Somero et al, 1983; Hochachka and Somera, 1984). However, the rapid response fenneri guinguedens to deadfalls (personal observations of baitbags from the Johnson Sea-Link submersible) suggests that these species are capable of rapid locomotory activity, albeit at levels lower than shallow water counterparts. The energetic cost of this high motility would presumably be repaid through the rapid location of a deadfall or baited trap. This material would represent a temporally and spatially unpredictable high energy food source in the food poor environment of the deep sea. The data presented here does not support or refute either the preferred substrate or temperature dependent hypotheses previously suggested to effect the bathymetric distribution of g. fenneri and guinquedens on the continental slope of the eastern Gulf of Mexico (Chapter 6)

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121 However, it does provide information on the metabolic rates of one of the major groups of decapod crustaceans that are important members of the continental slope megafauna. The data also suggests that temperature is the major determining factor of metabolic rate in benthic crustacea; not depth of occurrence which is a finding of major significance.

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1. 122 CHAPTER 8 SUMMARY The golden crab, Chaceon fenneri is one of the largest members of the family Geryonidae. Males may attain a size of 190 mm CW and weigh up to 1930 g; females are smaller and may reach a size of 156 mm cw and weight of 800 g. 2. The low incidence of individuals of each sex observed in the premolt or post-molt stage indicates that growth in Q. fenneri may be quite slow. Males showed no seasonal molting pattern, while greatest incidence of molting females were ob served in late summer and late winter. 3. Chaceon fenneri shows a pronounced annual reproductive cycle with a single batch of eggs produced each year. Oviposition begins in August and continues through October with eggs carried for approximately six months. Larval hatching occurs during February and March. size at sexual maturity is between 85-100 mm cw. 4. Fecundity had a positive correlation with increased animal size. The number of eggs per brood ranged between 114,000 and 4 3 5,000.

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5. 6. Mating in Q. fenneri follows molting and shows the typical premolt and post-molt cradling behavior characteristic of brachyuran mating. However, the duration of these events is greatly prolonged when compared to shallow-water species. 123 Both Q. fenneri and Q. guinguedens occur in the eastern Gulf of Mexico, but they are bathymetrically segregated on the continental slope. Chaceon fenneri predominates at depths of 311 and 494 m, while Q. quinguedens is present only at depths greater than 677 m. 7. Both species show a pronounced annual reproductive cycle. However, oviposition of Q. quinquedens occurs three months earlier than Q. fenneri. Larvae of both species hatch during early spring. Differences in the timing of reproductive events may reflect the dissimilar bathymetric distributions of each species. 8. The incidence of molting females and interrnolt non-ovigerous females of each species observed during the period of peak reproductive activity suggests that although the populations of both species may reproduce annually, individuals of each population may only reproduce biennially. The low frequency of reproduction observed may reflect the paucity of food items present in the continental slope environment and the corresponding effect that reduced energy levels have on growth rates.

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124 9. Field data suggests that temperature may affect the bathymetric distribution of each species. The minimum depth distribution of fenneri appears limited by the 12 c isotherm while the 8 c isotherm may limit the upper slope distribution of guinguedens. However, the presence of each species on different bottom types also suggests that substrate preference may be a factor affecting distribution. Chaceon fenneri was recorded only from coarse substrate off peninsular Florida while guinguedens was recorded from soft-silty substrate throughout the eastern Gulf of Mexico. 10. Oxygen consumption and Q10s fenneri and quinguedens measured at 6 c and 12 c indicate temperature dependent metabolic rates. No interspecific differences in oxygen consumption were evident at each experimental temperature. Both species are oxy-regulators over the P02 range of 110-20 mm Hg. The equivalent metabolic rates and Q10s measured for each species indicate that temperature may not be the major factor determining the segregated bathymetric distribution of these species on the continental slope. 11. Although the large size of fenneri and quinguedens make them attractive for possible th rate and low commercial utilization, the slow grow t 'ndicates that unregulated frequency of reproduc 10n 1 harvesting could rapidly deplete stocks.

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125 LIST OF REFERENCES R.G. 1985. Reproduction and its control. In: D.E. and L.H. Mantel, editors, The Biology of Crustacea, Volume 9: Integument, Pigments, and Hormonal Processes. Pp. 147-215. Academic Press New York New York. ' Aldrich, J.C. 1975a. On the oxygen consumption of the crabs Cancer (L.) .and Maia squinado (Herbst). and Physiology 50A: 223-228. Aldrich, J.C. 1975b. Individual variability in oxygen consumption rates of fed and starved Cancer pagurus and Maia sguinado. Comparative Biochemistry and Physiology 51A: 175-183. Blake, N.J., and L.J. Doyle. 1983. Infaunal-sediment relationships at the shelf-slope break. In: D.J. Stanley and G.T. Moore, editors, The Shelfbreak: Critical Interface on Continental Margins. Pp. 381-389. Society of Economic Paleontologists and Mineralogists Special Publication Number 33. Bowman, T.E., and L.G. Abele. 1982. Classification of the recent Crustacea. In: L.G. Abele, editor, The Biology of Crustacea, Volume 1: Systematics, the Fossil Record, and Biogeography. Pp. 1-27. Academic Press, New York, New York. Beyers, c.J.De B., and e.G. Wilke. 1980. Quantitative stock survey and some biological and morphometric characteristics of the deep-sea red crab Geryon guinguedens off south West Africa. Fisheries of South Africa 13: 9-12. Brett, J.R., and T.D.D. Groves. 1979. Physiological energetics. In: w.A. Hoar, D.J. Randall, and J.R. Brett, editors, Fish Physiology, Volume 7. Pp. 279-352. Academic Press, New York, New York. Briggs, J.C. 1974. Marine Zoogeography. McGraw-Hill Book Company, New York, New York. Pp. 1-475.

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137 Tyler, P.A., A. Muirhead, and J. Colman. 1985. Observations on.continuous reproduction in large deep-sea ep1benthos. In: P.E. Gibbs, editor, Proceedings of the 19th Marine Biology Symposium. Pp. 223-230. Cambr1dge Un1versity Press, Cambridge, United Kingdom. van W.F., M.C. Christman, C.E. Epifano, and S.D. Sulk1n. 1983. Growth of Geryon guinguedens (Brachyura: Geryonidae) juveniles in the laboratory. Fishery Bulletin, United States 81: 903-905. Vernberg, W.B., and F.J. Vernberg. 1972. Environmental Physiology of Marine Animals. Springer-Verlag, New York, New York. Pp. 1-346. von Bertalanffy, L. 1938. A quantitative theory of organic growth (inquiries on growth laws II). Human Biology 10: 181-213. Wear, R.G. 1974. Incubation in British decapod crustacea, and the effects of temperature on the rate and success of embryonic development. Journal of the Marine Biological Association of the United Kingdom 54: 745-762. Wenner, E.L., G.F. Ulrich, and J.B. Wise. 1987. Exploration for golden crab, Geryon fenneri, in the south Atlantic Bight: distribution, population structure, and gear assessment. Fishery Bulletin, United States 85: 547560. Wigley, R.L., R.B. Theroux, and H.E. Murray. 1975. Deep-sea red crab, Geryon guinguedens, survey off Northeastern United States. Marine Fisheries Review 37: 1-27. Wolvekamp, H.P., and T.H. Waterman. 1960. Respiration. in: T.H. waterman, editor, The Physiology of Crustacea, Volume I, Pp. 35-100. Academic Press, New York, New York. Yevich, P.P., and C.A. Barszcz: 1977. P:epa:ation aquatic animals for histopatholog1cal exam1nat1on. Un1ted states Environmental Protection Agency, Narragansett, Rhode Island. Pp. 1-20. zar, J.H. 1974. Biostatistical Analysis. Prentice-Hall, Inc. Englewood Cliffs, New Jersey. Pp. 1-620.

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138 APPENDIX

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139 APPENDIX 1. MATING BEHAVIOR OF CHACEON FENNERI IN CAPTIVITY Introduction Mating in Brachyuran crabs may occur immediately following ecdysis by the female (i.e. Callinectes sapidus, Cancer magister, Mennippe mercenaria) or may occur when the female is in the intermolt stage (i.e. Grapsus grapsus, Maja sguinado, Pinnotheres maculatus) (Hartnell, 1969). Post-molt mating often encompasses complex behavior patterns that include a premolt cradle and post-molt embrace of the female by the male. The embrace is associated with copulation and continues until the female exoskeleton has sufficiently hardened for resumption of normal activities. Conversely, intermolt mating does not exhibit complex courtship patterns and is often of short duration. The contrast in mating patterns has been attributed to differences in gonopore structure (Hartnell, 1969). Mating following female ecdysis has been reported in two species of Chaceon: longipes (Mori and Rellini, 1982) and guinguedens (Elner et al, 1985); however, the mating pattern of fenneri remains unknown. Although the pattern of mating following molting might b e expected to be present throughout the Geryonidae, intra-family differences have

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140 Appendix 1 (continued) been noted in the Xanth1'dae and MaJ1dae (Hartnell, 1969). The following observations are based on two separate episodes of molting and mating of fenneri held in captivity. Data of this nature when combined with field observations of population structure, reproduction and growth may provide additional insight to the life history of this slope dwelling species. Of particular importance may be the application of these observations to the low frequency of reproduction pattern proposed for fenneri. Materials and Methods Case 1 A female fenneri (91 rnm CW) in the immediate premolt stage (SO) was collected July 28, 1986 from the commercial fishery off southeast Florida (Chapter 3). This female showed characteristic premolt features: dark brown carapace and appendages, tips of antennae and antennules pink, and the epimeral suture of the carapace white and pronounced. Gonopores were of Type 1 (simple and slitlike) (Hartnell, 1967), an external feature associated with sexually immature females. In the laboratory, the female was held under reduced lighting in a refrigerated 45 1 aquarium (T = 9.5 "C). A mature male (168 mm CW) was also kept in the same aquarium. Both crabs were fed shrimp, scallop meats or

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141 Appendix 1 {Continued) squid approximately three times each week. Case 2 A female fenneri {126 mm CW) was collected in February 1988 from the eastern Gulf of Mexico {Area 4, 310 m, see Chapter 5). Aboard ship, the female was maintained with additional specimens in a refrigerated recirculating seawater system (T = 9.0 c) for return to the laboratory. Examination of external features indicated the intermolt stage (H), egg remnants in the pleopods, and type 3 gonopores with blackened margins; the latter two characteristics are indicative of recent reproductive activity. Upon return to the laboratory, this female was kept along with other fenneri and guinguedens in a refrigerated aquarium system at equivalent temperatures and eventually utilized in the respiration studies described in Chapter 7. All animals were fed shrimp, scallop meats, or squid three times a week. In November 1988, the female was transferred along with two additional females and three males to a refrigerated 780 gallon aquarium for public display at the Pier Aquarium, St. Petersburg, Florida. At this time, external carapace features that this female was in the early premolt stage (SN), an indication of imminent molting.

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142 Appendix 1 (Continued) Results Case 1 Precopulatory behavior was first noted on August 13, when the male formed a protective cage around the female with his walking legs. The male clasped the female by the carapace, dorsal side up, with the first pair of walking legs (2nd periopods). While carrying the female, the male continued to move about on the dactyls of the walking legs and feed at regular intervals. The female was not observed to feed during the premolt embrace. On September 9, the female molted with the male still forming a cage with his walking legs. Unfortunately, the female was unable to back out of the old carapace; hence, mating was unsuccessful. The soft shell female was dissected to observe the stage of ovarian development. The ovary was slightly swollen and cream in color, an indication of early development. This stage was confirmed through histological examination. Case 2 on December 10, 1988, the largest male in the aquarium (180 mm CW) formed a cage around the premolt female with his

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143 Appendix 1 (Continued) walking legs. The female folded all appendages close to the carapace and was carried dorsal side up beneath the male. The male used the first pair of walking legs (2nd periopods) to grasp the female between the first set of her walking legs (periopods 2 and 3). This carrying behavior continued for 28 days until the female molted. During this period, the male continued to feed at regular intervals and on occasion offered food to the female; however, the female was not observed to feed prior to molting. Molting began on January 7, 1989. Immediately prior to molting, the male released the female to the substrate and formed a protective cage around her with his walking legs, During this period, the male was observed to repel the two additional males present in the aquarium. The female remained motionless, dorsal side up until the suture at the posterior margin of the carapace was completely open. Typical brachyuran molting followed with the female slowly backing out of the old exoskeleton. The male remained in the cage position but did not assist with molting. Within two hours of the completion of ecdysis, the copulatory embrace began; the pair clasped sternum to sternum with the female inferior, ventral side up. The female was held odd the substrate by the male walking legs as previously described. Mating occurred with the extended abdomens of both crabs overlapped and the first pair of male pleopods inserted into corresponding female_gonopores.

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144 Appendix 1 (Continued) Following molting and the onset of copulation, the mated pair moved away from the discarded exoskeleton. At this time, the smallest male in the aquarium was observed to cradle and attempt copulation with the discarded exuviae. This peculiar behavior continued for approximately two hours until the male released the exoskeleton; this exoskeleton was removed for remeasurement of premolt morphometries. The copulatory embrace continued until February 10, 1989, a duration of 34 days. During this period the male fed actively and was observed to offer food to the female on many occasions. The female was observed to feed on three occasions while still in the copulatory embrace. The male walking legs were not always used to carry the female; often the female was carried by the male pleopods which remained inserted in the gonopores. The female broke free on February 10, 1989, when the new carapace had hardened sufficiently for increased locomotory activity. Upon examination, the new carapace was brittle and slightly flexible, and bright creamy gold in color. carapace width was 139 mm, an increase of 13 mm. Gonopores were type 3 with prominent blackened margins from abrasion during copulation. Blackened discoloration was also visible on the merus of the second periopods from abrasion by the male walking legs during the copulatory embrace.

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145 Appendix 1 (Continued) On July 7, 1989, a major electrical failure at the Pier Aquarium necessitated the return of all fenneri to the refrigerated aquarium system at the Department of Marine Science. The mated female did not survive this transfer and expired on July 8. Upon dissection, the ovary was found in the advanced development stage which suggests that oogenesis was proceeding towards oviposition. Discussion Mating of fenneri in the immediate post-molt stage conforms to one of the two basic Brachyuran mating patterns described by Hartnoll (1969). This pattern of long duration premolt and post-molt mate guarding has also been observed in longipes (Mori and Rellini, 1982) and guinguedens (Elner et al, 1985). This behavior has obvious survival benefits in that the soft-shell female is protected from potential predation during a period of great vulnerability. The long duration of the premolt embrace also suggests the presence of a pheromone released by the female to attract a potential mate (Ryan, 1967). of greater significance is that the second female was sexually mature when collected. Thus, molting of this female which had shown signs of previous reproductive activity suggests multiple mature instars rather than a single mature instar (Melville-Smith, 1987-C).

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146 Appendix 1 (Continued) The ovarian condition and gonopore stage of the first molting female infers that if successful, this molt would be the pubertal molt associated with the onset of sexual maturity. The 91 mm premolt carapace width of this individual was well within the proposed carapace width range of 85-100 mm that is the size at sexual maturity in this species (Chapter 4). As molting occurred in early September, a period when oviposition occurs in reproductively active females, this individual would be expected to undergo oviposition the following fall. This suggests that sperm may remain viable for up to 12 months in this species. Delayed oviposition following mating has also been reported for quinguedens (Elner et al, 1985). The second female was sexually mature when collected and the presence of blackened type 3 gonopores is indicative of previous mating activity. Of greater significance were the egg remnants on the pleopods which indicate that this female had recently hatched eggs prior to collection in February. This female did not undergo oviposition during the fall months after collection, yet the December period of molting conformed to molting patterns observed from southeast Florida and the eastern Gulf of Mexico. Thus, the temporal incidence of molting in both females held in captivity was temporally asynchronous to the reproductively active members of the sampled populations, yet showed a degree of synchrony with those members of the populations

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147 Appendix 1 (Continued) observed to undergo molting. The alternate pattern of molting and mating provides further evidence for the low frequency of reproduction pattern suggested for this species (see Chapter 4).


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