Food habits of pinfish, Lagodon rhomboides, from Anclote Anchorage, Florida

Food habits of pinfish, Lagodon rhomboides, from Anclote Anchorage, Florida

Material Information

Food habits of pinfish, Lagodon rhomboides, from Anclote Anchorage, Florida
Feinstein, Andrew
Place of Publication:
Tampa, Florida
University of South Florida
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vii, 101 leaves : ill. ; 29 cm.


Subjects / Keywords:
Fishes -- Food ( lcsh )
Lagodon rhomboides ( lcsh )
Fishes -- Florida -- Anclote Ancorage ( lcsh )
Dissertations, Academic -- Marine science -- Masters -- USF ( FTS )


General Note:
Thesis (M.S.)--University of South Florida, 1975.

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Source Institution:
University of South Florida
Holding Location:
Universtity of South Florida
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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
029063489 ( ALEPH )
01837474 ( OCLC )
F51-00012 ( USFLDC DOI )
f51.12 ( USFLDC Handle )

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FOOD HABITS OF PINFISH, LAGODON RHOMBOIDES, FROM ANCLOTE ANCHORAGE, FLORIDA by Andrew Feinstein A thesis submitted in partial fulfillment of the requirements for the degree of Master of Arts in the Department of Marine Science in The University of South Florida June, 1975 Thesis supervisor: Professor Ronald C. Baird


Certificate of Approval -Master's Thesis Graduate Council University of South Florida Tampa, Florida CERTIFICATE OF APPROVAL MASTER'S THESIS This is to certify that the Master's Thesis of Andrew Feinstein with a major in Marine Science has been approved by the Examining Committee as satisfactory for the thesis requirement for the Master of Arts degree at the convocation of June 1975 Thesis committee: Thesis supervisor: Dr. Ronald C. Baird Member: Dr. Thomas L. Hopkins Member: Dr. Harold J. Humm


DEDICATION This thesis is dedicated to my family: my wife, my mother, my brother, my sister and the memory of my father. ii


ACKNOWLEDGEMENTS Funds for this research were provided for in the form of graduate assistance from Florida Power Corporation. I would like to personally acknowledge Gene Gallaher who developed the program used for data analysis. He con-tributed many hours of his own time to the successful comple-tion of this thesis. I am deeply grateful. I would also like to thank the members of my committee for their help in this research. The following people assisted in identifying various food items: Dr. Humm, Theresa Bert, David Hamm, Robert Gibson, William Weiss, Ray Maurer, Joseph Johnson, John Studt, Robert Ernest, Thomas Perkins, and Scott Rodgers. Fellow members of the fish program were Billy Causey, Rick Dietz, Bob Fisher, Dean Milliken, and Ken Rolfes. Special thanks go to my wife, Betty, whose patience and understanding were greatly appreciated. iii


TABLE OF CONTENTS DEDICATION .... ACKNOWLEDGEMENTS .. LIST OF TABLES .... LIST OF FIGURES INTRODUCTION. LITERATURE REVIEW DESCRIPTION OF STUDY AREA METHODS AND MATERIALS Field Sampling. Laboratory Procedure. Laboratory Techniques The Dry-Weight Method RESULTS Food Items. Size Classes. Habitat .. 'Habitat and Size Class .. Seasonality DISCUSSION. . . . CONCLUSION. SUMMARY . LITERATURE CITED .. . . . iv ii iii v vi 1 3 8 13 13 14 15 18 21 23 49 56 60 7 4 85 93 96 98


Table 1 2 3 4 5 6 7 LIST OF TABLES Descriptions of the Monthly Stations (After Rolfes 1974). Size Classes Food Item List List of Algae Found in Pinfish Stomachs . Miscellaneous Food Items . Ontogenetic Progression of Food Items According to Habitat Seasonal Comparisons of Food Items Ingested by Pinfish Collected from Pensacola Bay, Florida (After Hansen 1969) v 11 21 22 25 48 72 91


Figure 1 2 3 4 LIST OF FIGURES Map of the Anclote Anchorage showing the stations sampled. Form used for recording data The percent frequency of diatoms found in the stomachs of pinfish collected from the four monthly stations. Relative importance of amphipods in the diets of pinfish of the four smallest size classes (13 mm to 90 mm). 5 Relative importance of decapod shrimp in the diet of pinfish of all size classes 6 7 8 9 10 11 Relative importance of decapod shrimp in the diet of pinfish collected from the four monthly stations . Relative importance of detritus in the diet of pinfish collected from the four monthly stations . Relative importance of detritus in the diet of the six largest size classes (51 mm to 164 mm) of pinfish. Relative importance of detritus in the diet of the six largest size classes (51 mm to 164 mm) collected from the four monthly stations The major food items ingested by pinfish . The major food items ingested by the two smallest size classes vi 9 16 26 31 34 36 42 44 46 50 52


LIST OF FIGURES (cont'd.) Figure 12 The major food items ingested by the six largest size classes 13 The major food items ingested by pinfish collected from the four monthly and two quarterly stations 14 The major food items ingested by each size class of pinfish collected from the four monthly stations A. Size class 1 (13 to 30 mm) B. Size class 2 (31 to 50 mm) c. Size class 3 (51 to 70 mm) D. Size class 4 (71 to 90 mm) E. Size class 5 ( 91 to 110 mm). F. Size class 6 (111 to 130 mm) G. Size class 7 (131 to 150 mm) H. Size class 8 ( 150 mm) 15 The major food items ingested by pinfish collected during the four seasons. 16 The major food items ingested by pinfish collected from the four monthly stations during each of the four seasons A. B. c. D. Station I. Station II. Station III. Station IV. vii Page 54 57 62 63 64 65 66 67 68 69 75 78 79 8 2 83


INTRODUCTION The Department of Marine Science of the University of South Florida undertook a long-term study of the effects on the Anclote estuary of the fossil fuel power plant con-structed by Florida Power Corporation. The Anclote estuary consists of various bottom types, ranging from sand to mud in which the dominant vegetation may vary among different areas (Ballantine and Humm, 1972). An important aspect is the study of fish populations. A t present 54 families and 110 species have been recorded (Rolfes et al., 1973). This thesis is a segment of the ichthyological pro-gram. The purpose of this research was to s tudy variations in the food habits of the pinfish, Lagodon rhomboides (Linnaeus). This particular species was selected because it is abundant and easily collected. It is present a t Anclote during ever y month of the year, and all sizes from post-larval fish of 10 to 15 mm to large adults of greater than 160 mm have b een collected. No w ork h a s e v e r been done on pinfish inhabiting the area of Anclote Anchorage or in any area between the Florida Keys and Crysta l R iver on Florida's w est coast. Moreover, studying variation i n h a b itats is important in d emonstrating the ability of an organism to utilize available resources. 1


This paper will discuss the range of habitats as well as the effect of ontogenetic variation and seasonality on the resource utilization by pinfish at Anclote. 2


LITERATURE REVIEW There have been numerous accounts of pinfish food habits going as far back as the turn of the century. Linton (1904) examined 150 pinfish and found that they ate mainly vegetation, crustaceans, bivalve mollusks, and fish. Smith (1907) and Hildebrand and Schroeder (1927) noted the varied character of the pinfish diet. From fish collected from Beaufort, North Carolina, Smith listed the important food items as being small fish, worms, mollusks, crustaceans, and seaweed. Hildebrand and Schroeder looked at 13 stomachs from Chesapeake Bay pinfish and found in order of importance vegetable debris, crustaceans, mollusks, and annelids. Reid (1954) reported that food items from pinfish collected at Cedar Key, Florida, consisted mainly of crustaceans although plant matter was also important. Other food items listed were mollusks, fish, plant and organic detritus, and mud. Darnell (1958) describes the pinfish as a "very selective feeder." The consumption of plant material and crustaceans was important although algae was considered an "incidental" item. Caldwell (1957) holds the same view concerning vege-tation. He notes that the bulk of the food consists of small animals, principally crustaceans, assoc i ated w ith the grass y habitat, and the ingestion of plant material "may be, at 3


least in part, incidentally ingested during the capture of animal food." Hansen (1969) lists crustaceans, polychaetes, chordates, vegetation, and sand as important items consumed by pinfish from Pensacola Bay, Florida. Odum (1971) looked at an undetermined number of pinfish from the North River Estuary in Everglades National Park, Florida. The major food items he found were crustaceans, mollusks, and vege-tation. Diener, Inglis and Adams (1974) examined 19 pin-fish stomachs from Clear Lake, Texas. Amphipods and organic detritus were found in the most stomachs. Other items were nematodes, polychaetes, copepods, mysids, lamellibranchs, fish, vascular plants, and mud and sand. Adams (1972) looked at primarily juvenile pinfish from Crystal River, Florida and found crustaceans, epiphytic algae, fish and detritus to be the major food items. Several workers have acknowledged the change in diet with growth. Reid (1954) compared three size ranges. The food of the smallest pinfish (15 to 50 mm) was exclusively crustacean. That of the intermediate group (51 to 100 mm) was crustaceans, mollusks, organic detritus and mud, and to a lesser degree fish and plant detritus. The largest group (101 to 128 mm) had eaten crustaceans and mollusks. Darnell (1957) divided his samples into five classes of size. The smallest size class (40 to 64 mm) ate mainly amphipods and some chironomid larvae. The next size class (65 to 74 mm) ate in descending order amphipods, vegetation, and chironomid 4


larvae. The next size class (75 to 99 mm) ate amphipods, vegetation, macrocrustaceans, and detritus. The fourth group (100 to 124 mm) ate a considerable amount of algae. Other food items were amphipods and macrocrustaceans. The largest size class (125 to 150 mm) also ingested a considerable amount of algae along with amphipods, detritus, and macrocrustaceans. Hansen (1969) looked at two size classes; those fish less than 76 mm and those larger. For the smaller fish crustaceans, polychaetes, and vegetation were the major food items. The larger fish ate vegetation, sand, chor-dates, polychaetes, and crustaceans. Adams (1972) was the first to study ontogenetic changes in detail. Pinfish were divided into 17 size classes in increments of 5 mm for the 13 smallest groups and 10 mm for the 4 largest for his study. At the Rocky Cove Station, Crystal River, crustaceans were the major prey item in fish in the first 5 size classes (6 to 30 mm). Epiphytic algae becomes important in size class 6 (31 to 35 mm) and completely dominates the diet of the next 5 size classes (36 to 60 mm). In size class 12 (61 to 65 mm) and 13 (66 to 70 mm) the dependence upon crustaceans and epiphytes is about equal. Fish becomes an important food item in size class 14 (71 to 80 mm) and increases in importance in the remaining 3 groups (81 to 110 mm). An ontogenetic progression in 3 stages for fish less than 110 mm is described by Adams which he found to be 5


similar for all habitats he looked at. Stage 1 is a car-nivorous one where post-larval fish consume zooplankton, primarily copepods. Stage 2 demonstrates a shift from the carnivorous habit to a more vegetative one. Epiphytic algae is the major food item found in fish from 21 to 70 mm. In an area of thermal effluent fish of this size range sub-stituted detritus for the epiphytes. The third stage is a return to carnivorous habits with first shrimp and then fish becoming the major prey item. Carr and Adams (1973) note that pinfish are one of the few fishes that take advantage of plants as food during one of their ontogenetic stages. Darnell (1961) describes an ontogenetic progression for pinfish which involves small crustaceans, followed by detritus, then vegetation. Other authors without referring to ontogenetic pro-gression reveal similar changes. Odum (1971) looked at 12 small pinfish (39 to 61 mm) and found only animal food. Gunter (1945) and Springer and Woodburn (1960) attest to the vegetative habits of large pinfish. Gunter looked at 8 pinfish, 150 to 285 mm in length, and observed that 7 had eaten plant material, and one had eaten clams. Although Springer and Woodburn did not list the sizes of the pinfish they examined, they do note that a 140 mm specimen ingested a large mass of Diplanthera. Several authors refer to a preferred habitat for pin-f i sh. Caldwell (1957) des cribed the i mportance o f s h allow, vegetated areas in pinfish ecology, noting that pinfish are 6


more abundant in areas such as these than in areas of no vegetation. He referred to the latter as "the secondary center of local abundance." These habitats are characterized by either natural objects such as rocks and mangroves or man-made objects such as docks, pilings, and breakwaters which afford cover and support invertebrate growth. The habitats from which pinfish were collected for the study by Gunter (1945) were not described; however, he notes that "the lack of plant material on the Gulf beach probably accounts for the absence of pinfish in that environment." Both Hansen (1969) and Adams (1972) describe their collect-ing stations as grass flats. Odum (1971) notes the abun-dance of pinfish in seagrass and Udotea-covered areas. Cameron (1969) noted that large pinfish are less abundant in the shallows, and citing data from Darnell (1958) on ontogenetic change in food habits, observes that perhaps movement from one environment to another is regulated by change in diet. Very few workers studied habitat variation per se as a factor in diet changes. Adams (1972) observed juvenile pinfish of a certain size range ate algae in non-thermallyaffected areas and detritus in a thermally-affected one. Odum (1971) mentioned that fish from one area ate crustaceans and bivalves while those from a second area ate algae and vascular plants as well. He doesn't mention if fish from both groups were in the same size range. 7


8 DESCRIPTION OF THE STUDY AREA The Anclote Anchorage, an area of approximately 5 square kilometers, is at the mouth of the Anclote River, just northwest of the town of Tarpon Springs on the Florida Gulf Coast. To the west are Anclote Key, North Key, and Dutchman Key providing a barrier between the river and the Gulf of Mexico. The area is characterized by extensive seagrass beds wherever light penetration to the bottom is sufficient for them and where currents and consequent drifting sands do not prevent their establishment (Ballantine and Humm, 1972). The dominant seagrasses are .. turtle grass, Thalassia testudinum Konig, manatee grass, Syringodeum filiforme and shoal grass, Diplanthera wrightii (Ascherson) Ascherson. Figure 1 is a map of the anchorage showing sampling locations of all stations. Monthly sampling of four stations was done in order to compare seasonal and diurnal differ-ences between shallow and deeper regions in areas of grass and sand. Table 1 describes these four monthly stations with respect to water depth, substrate, and vegetation.


Figure 1. Map of the Anclote Anchorage showing the stations sampled. Roman numerals and circles represent the stations that were sampled monthly. Triangles represent the six shore stations sampled quarterly. "Dead Fish Pass" is denoted as such. 9


10 0 p D Pf ?' = I (.., ./ 6 0 ___;';, -u,Ji ) r / y ; f)\ 'l f (J _; ,.


TABLE 1 Descriptions of the Monthly Stations (After Rolfes 1974) Station Depth (Mean Low Water) I II III IV 0.7 m 1.8 m 1.5 m 0.6 m Shallow grass-Syringodium filiforme is dominant. Sediment is muddy sand. Deep sand-No vegetation. Sediment is hard sand. Deep grass-Syringodium filiforme is dominant. Sediment is muddy sand. Shallow seasonal grassThalassia is dense in the warmer months and bare sand in the colder. Sediment is sand and shell. Station I is located south of the river mouth and is characterized by a bed of manatee grass. Station II is in an area adjacent to the outfall canal. It is one of the two deep stations. No seagrasses are present. Station III is located 500 m from Station II. The main seagrass is manatee grass. Station IV is the other shallow station. It is close to the south end of Anclote Key in an area where turtle grass is abundant especially in the warmer months of the year. Two areas were sampled quarterly. Because they were sampled less frequently and less consistently than the 4 monthly stations, the data from these areas were treated in 11


a more general way. The first of these areas was a bayou known as "Dead Fish Pass." It will be referred to in this paper as Station V. It is situated on the north shore of the Anclote River adjacent to the intake canal. There is extensive mangrove growth bordering the area. There is an absence of aquatic vegetation in the bayou proper although the shallow marginal areas are vegetated by the terrestrial plants, Spartina alterniflora Loiseleur-Deslongchamps, and Juncus roemarianus Scheele (Baird et al., 1973). Water depth varies from 1 to 1.5 m at high tide to almost 0 m at low tide. In addition to the bayou quarterly sampling using seines was done on 6 shoreline locations. Data from these locations are presented together, and the locations themselves are jointly referred to as Station VI. 12


METHODS AND MATERIALS Field Sampling Pinfish were collected from the 4 monthly stations using trammel nets and trawls. The trammel net, 91 m long, was set for 45 minutes. During this period of time the bottom was sampled on either side of the net at a distance of 75 rn with a 3 rn otter trawl being pulled from behind at a speed of approximately 2.5 knots. Duplicate samples were taken at each station. For a more detailed description see Baird et al. (1972). "Dead Fish Pass" was sampled utilizing beach seines and a fyke net and t aking advantage of extreme tidal cycles. A detailed description of this procedure is found in Baird et al. (1973). The shorelines were sampled with seines having mesh sizes of 0.32 em and 0.64 ern. Seine length was 5.54 m for the 0.32 em mesh and 9 .84 rn for the 0.64 m mesh. Fish were fixed in the field in 10 to 20% formalin and later rinsed in water separated to species and preserved in 40% isopropyl alcohol. 13


Laboratory Procedure The pinfish examined were preserved and were selected from catches representing 657 collections. Only fish collected during the daytime were examined. Caldwell (1957) observed that pinfish refuse bait and become inactive after dark. Darnell (1958) describes young and adult pinfish as daytime feeders. Odum (1971) noted that "every Lagodon taken in night samples had an empty stomach." After con-firming the diurnal feeding periodicity, no further night samples were examined. For the monthly samples all trammel collections and usually one of the trawls were used. The two trawls in each set were so close together, both in time and location, that it was felt that one would be sufficient. number of collections examined was 153. The total If there were as few as 10 fish in a collection, all of the stomachs were examined. However, collections with larger numbers of fish were subsampled. The subsampling technique assured that at least 50% of the fish were examined. The fish were first measured and for each pair of fish within a 5 mm size increment, 1 was examined and the other discarded. The size increment of 5 mm allowed each of the 8 size classes used in the study to be adequately represented if present. 14


Laboratory Technique All fish were measured to the nearest millimeter in standard length according to Hubbs and Lagler (1958), and weighed to the nearest 0.1 gram on a P 160 Mettler balance. Fish were opened by inserting the tip of one blade of a fine scissors into the anus and cutting anteriorly to the operculum. Dorso-ventral cuts were made at each end of the incision. This allowed for the body wall to be pulled away exposing the visceral cavity. The stomach was removed from the intestine by cutting anterior of the pyloric caecae. It could then be removed by cutting the esophagus. The stomach was opened by making a small cut at the dorsal-posterior end and cutting from this point anterior through the esophagus and posterior through the pylorus. This enabled the stomach to be cut longitudinally without damaging the contents which oould then be removed. The contents were placed upon several drops of de-ionized water in a petri dish and examined under a dissecting microscope at a maximum power of 30 X. Food item biomass was estimated using the dry-weight method (see Hynes 1950 for a review of methods for evaluating food items in fish). When each food was identified, it was transferred to either a pre-weighed cover slip or a pre-weighed aluminum weighing pan and placed in an oven at a temperature of 60 C for at least 24 hours. The weighing pans and the cover slips were then weighed on a Mettler H20 to the nearest 0.1 mg. The data was recorded on forms (Figure 2) and later transferred to computer cards. 15


1 6 Figure 2. Form used for recording data.


COLLECTION NO. ------Date Time Season --------------Station ; Habitat ----------FISH NO. ----------Length _____ cm.; Weight ______ g. Otoliths Size ----FOOD ITEMS Plant material Diatoms Nematodes Polychaetes Gastropod mollusks Bivalve mollusks Copepods Calagoid copepods Amphipods Caprellid amphipods Ostracods Isopods Crabs Decapod shrimp Mysids Distance from focus to annuli: 1. -------2. ______ 3. -------Tare (g) Crustacean larvae Unidentified crustaceans Lower chordates Fish Other Detritus TOTAL WEIGHT OF STOMACH CONTENTS NOTES: Distance between: 1. lst&2nd annuli ___ 2. 2nd&3rd annuli -----3. Last annulus to outer margin ----Gross wt. (g) Net wt. (mg) 17


The Dry-Weight Method The advantages of estimating food biomass in terms of dry weight are: 1. Its directness. 2. Real values can be obtained rather than estimates from indirect methods. 3. It is effective for all but the smallest size classes. 4. The oven-drying removes the water which can be a major source of bias. 5. It is quantitative. This method was used to express diet variability because of these reasons. There were, however, various ways in which the data could be biased and these are discussed below. 1. There was a potential bias due to the pinfish size. This results from the effect large pinfish, although few in number, would have upon an entire data set which included fish of all size classes. This is especially important since ration, total metabolism, and stomach volume are exponentially related to length. This bias would have its greatest impact, for example, in compar-isons betwee n habitats or seasons. In both instances an overabundance of large individuals would be non-representative for overall comparisons. 2. There was a possible bias due to variations in 18


sample size of pinfish. This source would be most apparent when comparisons within size classes are made between habitats or seasons. Fish of particular size ranges may be most abundant in one habitat or present only during certain seasons. Diet comparisons of fish from different habitat or season may be masked by a large number of fish peculiar to only one habitat or season. 3. There was a potential bias resulting from prey size. An unusually large item could affect every comparison in which it was involved. 4. There was a bias due to one-time occurrences. Rarely, a particular food item which occurred only once was abundant in such great amounts that it accounted for high percentages which affect relative values for other prey items for entire data sets on a yearly or total basis. 5. There was a bias due to uneven distribution of densities between food items. Sometimes the weight percent of total stomach contents was influenced by not onl y the amount ingested but als o by a high amount of heavy material accompanying it. An example would be detritus where s and constitute s ove r 90% of t h e total w eight A less extreme sample would be the smalle r nominal difference i n densities between food 19


items. For instance, between fishes and animals possessing a hard exoskeleton. Both of the above could lead to weight values which do not reflect an actual picture of the relative importance of the food items. 6. There was a possible bias resulting from the effect of digestion. This was evident in two ways. Detritus contained non-digestible compo-nents such as sand, shell, and quartz. The weight of this item would not apparently change since it resists enzymatic breakdown. On the other hand, any item which was importantly utilized for food would be seen in various stages of digestion. Actual weight, then, does not necessarily represent fresh or undigested weight. 7. The dry-weight method was not accurate for the two smallest size classes. method was used instead. The percent frequency Despite the shortcomings listed above, the dry-weight method was selected over others because this method seemed well-suited to evaluate the stomach contents and facilitate comparisons among various parameters. 20


RESULTS A total of 808 pinfish ranging in size from 13 mm to 164 mm were examined. These were allocated to 8 size ranges (Table 2). Size Class 1 2 3 4 5 6 7 8 TABLE 2 Size Classes Size Range 13-30 31-50 51-70 71-90 91-110 111-130 131-150 151-170 The total dry weight of all food items ingested (mm) amounted to 22,605.25 mg. The m ean value was 27.97 mg per fish (Table 3). These values considered by themselves without regard to habitat, size, or time of year can be highly misleading. Moreover, by eliminating from the c alculations 6 fish which had extraordinarily h igh weights for stomach contents the total figures change considerably. 21


Food Item Plant material Diatoms Hydrozoans Nematodes Polychaetes Gastropod mollusks Bivalve mollusks Copepods Calagoid copepods Amphipods Caprellid amphipods Crabs Decapod shrimp Mysid shrimp Crustacean larvae Unidentified crustaceans Sea urchins Lower chordates Fish Other Detritus Unidentified TOTAL WEIGHT = 22,605.25 mg NUMBER OF FISH = 808 AVERAGE WEIGHT OF FOOD/FISH TABLE 3 Food Item List Weight (mg) 5522.37 147.54 796.13 19.77 446.17 3.07 5.84 392.58 14.03 263.90 1233.36 121. 4 7 742.84 72.52 85 3. 52 227.14 2444.05 75. 38 8716.15 401.76 27.98 mg Mean (mg) 6.83 0.18 0.99 0.02 0.55 0.49 0.33 1. 53 0.15 0. 92 0.09 1. 06 0.28 3.02 0.09 10.79 0.50 Percent of Total Weight 24.43 0.65 3.52 0.09 1. 9 7 1. 74 1.17 5.46 0.54 3. 29 0. 32 3. 7 8 1. 00 10.81 0.33 38.56 1. 7 8 Incidence 308 114 33 80 68 9 72 135 4 209 29 19 10 3 4 38 41 2 5 58 50 217 83 N N


Of these 6 fish, 3 had eaten other fishes, one a sea urchin, and the other two were full of detritus. The total weight of their stomach contents was 3,579.81 mg or 15.84% of the total for all stomachs. After taking this into consideration, the new values come out to 19,025.44 mg with a mean of 23.72 mg per fish. Food Items Plant Material Plant material is the single most important organic item ingested in terms of weight and frequency of occurrence. Three hundred eight fish, 38% of the total, ingest plant material o f some type, and it accounts for about 29% of the total weight of food items. The most common ingested plant was Syringodium filiforme, the manatee grass. This i s not surprising since two o f the regular monthly stations (I and III) were in areas of Syringodium beds. Shoal grass, Diplanthera wrightii, was e aten occasionally; but not as frequently as Syringodium. D iplant hera and Syringodium do not normally grow within close proximity of each other (Humm, personal communication). Turtle grass, Thalassia t estudinum, w a s r arely eaten. It is abundant i n t h e estuary and p resent duri n g the war m e r months at Station IV. O ccastionally a few small pieces were found, but no stomach ever contained the quantities c omp arable to Syringodium. Benthic a lgae, particularly t h e reds and browns, were common in pinfish stomachs. During the colder months the 23


seagrass leaves partially die off, and algae were more abundant in the stomachs of the larger fish. Small epi-phytic algae such as Ceramium byssoideum, and other Ceramium species, and blue-greens were commonly found in association with detritus or decaying matter. In most instances the occurrence of algae under these circumstances was not noted in the total incidence; so the number of fish previously referred to which ate plant material is somewhat less than the actual total. Algal species which were identified are listed in Table 4. Diatoms Benthic diatoms were found in 114 pinfish. This food item was most commonly ingested along with detritus as well as other items. Figure 3 describes the percent frequency of diatoms with respect to each station. The highest values were at Station IV and I with 42.0% and 12.6% respectively. Species identified were Actinoptychus splendens (Shadbolt) Ralfs, Gyrosigma balticum (Ehrenberg) Cleve, Rhabdonema adriaticum Striatella unipunctata Lyngbye, Synedra ulna Ehrenberg (Nitsche) and Synedra ulna var splendens. Foraminifera Two species of forams, Rotalia beccarii (Linne) and Sorites marginalis (Lamarck) were found from 17 pinfish. In all cases they were ingested with detritus. 24


TABLE 4 List of Algae Found in Pinfish Stomachs CYANOPHYTA Anacystis aeruginosa (Zanardini) Drouet and Daily Calothrix crustacea Thuret Microcoleus lunbyaceus Crouan Schizothrix arenaria (Berkeley) Gamont Schizothrix arenaria ecophene Microcoleus chthonoplastes Schizothrix calcicola (C. Agardp) Gamont CHLOROPHYTA Acetabularia crenulata Lamouroux Chaetomorpha gracilis Kutzing Cladophora delicatula Montagne Derbesia lamourouxii (J. Agardh) Solier Derbesia vaucheriaeformis (Harvey) J. Agardh Enteromorpha Penicillus PHAEOPHYTA Giffordia mitchellae (Harvey) Hamel Ectocarpus siliculosus (Dillwyn) Lyngbye Sphacelaria furcigera Kutzing Sphacelaria Stictyosiphon subsimplex Holden RODOPHYTA Acrochaetium Ceramium byssoideum Harvey Ceramium sp. Champia parvula (C. Agardh) Harvey Fosliella farinoas var solmsiana (Lamouroux) Howe Gonotrichum alsidii (Zanardini) Howe Hypnea musciformis (Wulfen) Lamouroux Hypnea Jania adherens Lamouroux Jania capillacea Harvey Jania Laurencia obtusa (Hudson) Lamouroux Polysiphonia hemisphaerica Areschoug var boldii Wynne et Edwards Polysiphonia subtilissima Montagne Polysiphonia sp. Spyridia filamentosa (Wulfen) Harvey 25


Figure 3. The percent frequency of diatoms found in the stomachs of pinfish collected from the four monthly stations. 26


--, DIATOMS 50 45r-40->-u z 35-w 0 W3Q0:: LL. w 25(!)

Hydrozoans Hydrozoans, the majority belonging to the Circular-idae, were eaten by 33 pinfish. In most instances, the hydroid was ingested along with epiphytes and/or detritus, but in several of the fish it was the principle food item. Nematodes Nematodes were ingested by 80 fish. For the most part they incidentally ingested along with detritus; however, they were occasionally found in detritus-free stomachs of the smallest individuals. Polychaetes Sixty-eight pinfish ate polychaetes, either wholly or in parts. Frequently only a tube was encountered or pieces of tissue which were taxonomically unidentifiable. This prey item accounted for 4.18% of the total weight. Occasionally a worm was found with numerous amphipods attached. Pinfish may possibly act as scavengers at times, and eat organisms that are already dead. Gastropod Mollusks Gastropod mollusks were not a very important food item and were found in quantity in only 9 fish. stomachs contained numerous developing larvae. Bivalve Mollusks One of the Bivalve mollusks were an abundant prey item in 72 stomachs. Frequently they occurred as many small individuals 28


consumed with epiphytic algae or hydrozoans, but in a few instances large individuals, such as Anadara transversa (Say), accounted for most of the stomach volume. A few times tissue identified as a bivalve muscle was found with no evidence of a shell. In at least one fish, juvenile scallops, Argopectin irradiens (Say), were found in the intestine but not in the stomach. It is possible that bivalves are ingested readily, but only the smallest or those with the weakest shells are utilized as food. Copepods Benthic copepods representing the orders Harpacticoida and Calanoida were frequently found. The most common one was the calanoid, Pseudodiaptomus coronatus Williams. It has been suggested that this species may be bentho-pelagic (Jacobs, 1961). In the larger pinfish copepods were inci-dental in the ingestion of detritus. In pinfish less than 30 mm they were an important prey item. hole-planktonic copepod encountered. Calagoid Copepods Very rarely was a Ectoparasitic calagoid copepods were found in abundance in one juvenile pinfish collected from the beach habitat. The fish measured 50 mm SL and had consumed more than 50 individuals. Cleaning behavior by pinfish has been observed in nature (Breder, 1962) and described for juveniles of a closely related species, Diplodus holbrooki (Bean) (Carr and Adams, 1972); it would be premature, however, to ascribe 29


cleaning behavior to this particular incident. Amp hi pods Amphipods were perhaps the most important food of post-larval and juvenile pinfish. They were found in abundance in all but the two largest size classes. They were especially important in fish smaller than 91 mm. Figure 4 shows abundance of amphipods in terms of percentage of total weight and percent occurrence in the 4 smallest size classes. In size class 1, amphipods accounted for the greatest percentage of total weight. Values for percent occurrence for all 4 groups ranged from 29.01% for size class 4 fish to 51.11% for size class 2. In the 4 largest size classes weight percentage and percent occurrence drop off significantly. Caprellid Amphipods Twenty-nine pinfish, most smaller than 91 mm, ate caprellid amphipods. Crabs All crabs including hermit crabs were included in one category. Although only 17 fish ate crabs they were an important food item when encountered. The average weight of this food item was 0.32 mg. Pinfish in size class 5 (91 to 110 mm) accounted for the greatest consumption. Five fish in this size range ate crabs totalling 193.77 mg for an average of 38.75 mg per fish, which compared with 23.18 mg 30


Figure 4. Relative importance of amphipods in the diets of pinfish of the four smallest size classes (13 mm to 90 mm). 31


w (.!) 50 z w (.) 0::: w a.. Size Class (mm. ) 13-30 AMPHIPODS D = PERCENTAGE OF TOTAL WEIGHT 0 = PERCENTAGE FREQUENCY 31-50 51-70 71-90


for the size class as a whole. Decapod Shrimp Decapod shrimp were the third most important item in terms of weight. One hundred three fish consumed shrimp for a total weight of 1,233.36 mg which was 6.48% of the total, (i of 1.54 mg per fish). It is an important food item in size classes 2 through 6. Figure 5 compares values of decapod shrimp expressed as a percentage of the total weight for each size class. It forms the most substantial portion of the diet in size classes 3 and 6. Figure 6 compares the number of shrimp eaten at each of the 4 monthly stations. The 2 grass stations (I and III) show the greatest amount eaten. Fish from Station IV ate considerably less, and those from Station I I virtually none at all. Mysid Shrimp Mysid shrimp were not frequently found. Only 3 fish had consume d significant quantities. These fish were col-lected from Station II on 26 October 1971 in the afternoon. They measured 120, 116, and 124 mm SL, and the mean weight of mysids found for each fish w a s 39.75 mg. The mysid w a s identified as Mysidopsis bigelowi Tattersall. Crustacean Larva e Crustacean larvae were normally found i n post-larva l and juvenil e fish or as incidental i tems in d etritus. 33


Figure 5. Relative importance of decapod shrimp in the diet of pinfish of all size classes. 34


DECAPOD SHRi rv1P 20 -I-:c (.!) w 15-3: r--....l -<( I0 IIJ... 10-I 0 -w 1I z I w 5(..) I 0::: w -a.. -I -l I I 0 Size Class 13 -30mm. 31-50 51--ro 71-90 91-110 111-130 131-150 > 151 n 45 168 127 137 156 86 1 2


Figure 6. Relative importance of decapod shrimp in the diet of pinfish collected from the four monthly stations. n = the number of pinfish examined from each station. 36


1 DECAPOD SHRiiviP 2 0 I r :r: (..!) w 15-r---_J 0 r I 10-j I I w I (..!) r---z w 5u 0:: I.LJ Q.. I l n l I 0 l Station T I IT ill N I ... n I 190 90 242 176 I


However, during one sampling period one species was eaten in quantity by older fish. Stomachs taken from large fish caught from both deep stations (II and III) were literally packed with thousands of planktonic porcellanid crab larvae. All fish had been collected in the trammel net which indicated that they had been feeding in various levels of the water column. The trammel net also selects for larger pin-fish. Every fish examined was greater than 100 mm SL. Very few pinfish were caught in the accompanying trawls, and these showed no evidence that they had been utilizing this resource. The presence of the crustacean larvae was significant for two reasons. First, it appears that almost all of the fish collected from these two stations had abandoned the "normal" benthic feeding pattern. Only 3 fish had not con-sumed the larvae. They were all from Station III, had eaten plant material, and were collected in the earliest trammel set of the day. Secondly, it seems that the presence of the larvae attracted large numbers of pinfish to the general area. It is impossible to determine the geographic e xtent of the larval mass since neither fish sampling of the two shallow stations nor plankton sampling in the entire estuary was done on that day. It is significant, however, that the two trammel nets at the deep sand station, which incidentally were the latest sets of that day, yielded the two highest totals of pinfish for the entire monthly program from this station. 38


Unidentified Crustaceans This category consisted of solitary parts such as appendages, or crustaceans either too digested or missing sections so that identification was not possible. The total weight was 72.52 mg of which one food item accounted for almost 50%. Other Crustaceans Occurrences of other crustaceans such as ostracods, osopods, or cumaceans were rarely encountered. Lower Chordates Five of the larger fish ate lower chordates. The total weight of this food item was 227.14 mg. Fish The degree in which pinfish ate other fishes was difficult to assess. The digestive processes act more rapidly on fish than they do on animals with exoskeletons of shell or chiton. Only when tissue could be positively identified as fish through form, fins or rays, bones, or scales would it be listed as such. Otherwise, tissue that could conceivably have been a fish, but with uo distinguishing characteristics was listed as "unidentified." Fish were not found as frequently as some other food items. Parts of or entire fish were found in only 55 pin-fish, and in 20 of these occurrences only scales were present. The presence of scales and the absence of any 39


other tissue could mean that a fish was consumed and everything but the scales was digested, or that scales were ingested separately. Although the literature has never described a scale-eating habit in pinfish, it has confirmed this peculiar feeding habit for other fishes (Kner, 1860, p. 34; Breder, 1927, p. 127; Marlier and Lelup, 1954; Fryer et al., 1955; Springer and Woodburn, 1960, p. 22; Gery, 1964, pp. 459-460; Holse, 1966; Roberts, 1970, 1973; Major, 1973; Carr and Adams, 1972, 1973, pp. 518, 526-527). The bayou was the habitat which yielded the best data on Lagodon fish-eating habits. A small sub-sample of fish was examined from a spring fyke-net collection. Every stomach contained fish. The weight of the fish from three of the stomachs comprised 77% of the total weight of all fish eaten from all stations. Three genera were identified, Gobiosoma, Anchoa, and Eucinostomus. Detritus I use the term detritus to describe ingested matter, consisting of decaying organic material mixed in with a considerable amount of sand. The major organisms associated with this were diatoms, nematodes, copepods, and microscopic epiphytic algae. Detritus was found in 217 stomachs and comprised 40.31% of the total weight of all ingested items. Detritus was ubiquitous in the estuary and was found in fish collected from all habitats. However, like plant 40


material the majority of occurrences was restricted to certain habitats. Figure 7 compares the amount of detritus in percentage of weight for each station. The two stations which are characterized by.low density of seagrasses are those in which the greatest amount of detritus was ingested. Figure 8 compares detritus consumed with respect to size class. The percentage of total weight for size class 4 was the largest of any when compared against similar values for other size classes. Figure 9 shows the importance of station with respect to size class. Except for size class 1 the lowest value of detritus consumed for any size class from Station IV is 45.50% for size class 8 fish. Station II fish do not ingest detritus in considerable amounts until size class 5 with 35.74%, and the values increase with each succeeding size. Four size classes (3 through 6) from the shallow grass station had values of 20.82 to 32.28% of the total weight of items ingested. No size class of fish from Station III ingested substantial amounts of detritus. Other This category includes food items not eaten in abundance. Table 5 lists them in phylogenetic order, number of occurrences, and total weight. Forty fish had eaten these items for a total weight of 926.28 mg. The unusually high weight was due to the ingestion of 2 sea urchins, 41


Figure 7. Relative importance of detritus in the diet of pinfish collected from the four monthly stations. 42


I DETRITUS 100 J 959085I-80-:::r: n (.!) 75r--w 70-3: _J 65<{ 60-5 55I-50-I..L. 45I 0 I I 40-I w I (.!) 35<{ I-30-z w 25(.) I 0::: 20I w I a.. 15-10-I I 50 r-1 Station I II Ill N


Figure 8. Relative importance of detritus in the diet of the six largest size classes (51 mm to 164 mm) of pinfish. 44


85 I-80 ....J 60-;c::J: 5 55I-50-ts 45-w 40-(!) <::( t-..:: z w (_) 0:: w a_ 353025-20-15-10-Size Closs (mm.} DETRITUS ] n I 51-70 71-90 91-110 Ill -130 131-150


Figure 9. Relative importance of detritus in the diet of the six largest size classes (51 mm to 164 mm) collected from the four monthly stations. n = the number of pinfish of each size class examined from each station. 46


,.... ...;t 100 1 90 85 80 .._ 75 :r: (.!) 70 w _J 0 .._ lL. 0 w (.') 30 :z w 0 0::: w a.. n = Size Class mm.) DETRITUS 47 10 46 53 33 II 35 33 40 25 24 32 26 25 79 16 13 7 28 14 5 I 3 3 51-70 71 90 91 II 0 111-130 131-150 151-170


weighing 798.30 mg and 55.22 mg respectively. The next highest single weights were 14.48 mg for Bursatella egg-cases and 11.36 mg for Nemertine flatworms. None of these food items was significant in numbers, or, with the excep-tion of the sea urchins, significant in weight. TABLE 5 Miscellaneous Food Items Category Incidence Sponges 1 Cnidarians 1 Flatworms 8 Sipunculids 3 Other worms 4 Embryonic gastropods 1 Larval Limulus 1 Barnacles 5 Chironomid larvae 2 Bryozoans 1 Chaetognaths 1 Sea urchins 2 Ascidian larvae 1 Egg cases 10 Unidentified Weight 21.50 0.86 5.93 1. 62 14.98 1. 57 3.55 853.52 24.37 Tissue which could not be adequately identified due to 48 digestive decomposition was listed separately. In some cases digestion was too advanced to distinguish between plant and


animal material, but for the most part this category consists of animal tissue. Unidentified tissue was found in 83 fish for a total weight of 401.76 mg and a mean of 0.50 mg. Empty Forty stomachs were found to contain no food at all. Size Classes Table 2 presents the breakdown into 8 size classes. Figure 11 shows size classes 1 and 2 and the major food items associated with each in terms of percent frequency. The two smallest size classes have in common plant material, copepods, and amphipods as the important food items. In addition, size class 2 fish ate a considerable amount of detritus. It was found in 28.89% of fish in this size range. Copepods and amphipods were the two most important prey items. For the two size classes copepods were found in 66.19% and 24.44% of the stomachs; amphipods in 38.03% 49 and 51.11%; and plant material was found in 22.54% and 26.67% Figure 12 describes food items for the remaining 6 size classes. The values are in percentages of total weight. Detritus is ingested considerably in all but the largest size class. Size class 3 fish are crustaceans, mainly amphipods and decapod shrimp, and in addition to detritus, size class 4 was the size range in which detritus was eaten in the greatest percentage of the total weight 61.41%. Amphipods, polychaetes, and fish were other important


50 Figure 10. The major food items ingested by pinfish.




Figure 11. The major food items ingested by the two smallest size classes. Legend of food items in Figure 10. 52


>0 z w a w a::: 1..1.. w (!) j:! z w 0 a::: l.JJ a_ S ize Class (mm.) 13-30 31 -50


Figure 12. The major food items ingested by the six largest size classes. Legend of food items in Figure 10. 54


U"\ U"\ ...J lJ.... 0 LJ.l (.!) 35 z 30 w 25 20 w a.. Size Class (mm.} 51-70 71-90 91-110 111-130 131-150 151-170


food items. Size class 5 is the first one in which vege-tation is eaten in any quantity. It accounts for 21.03% of the total which is still less than the percentage for detritus. Polychaetes is the other important food item. In size class 6 the percentage of plant material (39.57%) exceeds that of detritus (21.12%). Decapod shrimp account for 13.42%. Detritus and plant material dominate the diet of size class 7 fish with 52.75% and 34.26%, respectively. Size class 8 was represented by only 12 fish, and there appeared to be greater variation in kinds of food items. Nine fish had eaten plant matter which accounted for 25.58% of the total. Four fish had eaten detritus for 9.72%, and 3 fish had eaten lower chordates for 10.45%. One stomach contained a fish, and another a sea urchin which accounted for 5.62% and 46.02%, respectively, of the total weight. Habitat The 6 habitats from which the pinfish were collected are quite different from each other. Figure 13 compares the major food items within each habitat. Vegetation was the most important food item in Stations I and III, while detritus was the major item ingested by fish in Stations II and IV. Fish from Station I ingested detritus and amphi-pods as well while at Station III. Crustaceans, decapod shrimp, and porcellanid crab larvae were the other important prey items. 56


Figure 13. The major food items ingested by pinfish collected from the four monthly and two quarterly stations. Legend of food items in Figure 10. n = the number of pinfish examined from each station. 57


Station I n 190 ... . . .. . . ... . . ... ... .. . . . . . . ... . . = . . .. :: . o .. . . . .. . .. . :. : . -:. . . .. . . II ill 90 242 .. . . .. .. .. .. : .. .. . .. .. . .. . .. ... . ... . ... : . ..: .. .. .. . .. : . .. . ... . . . .. .. . N 176 26 81


Over 75% of the total weight of stomach contents was destritus for fish from Stations II and IV. Crustacean larvae and mysids, both one-time occurrences, constituted the next highest percentages of food items from Station II. Station IV fish were eating plant material and polychaetes. The other two areas were sampled much less frequently and consistently than Stations I through IV. Only 26 fish collected from the bayou (Station V) were examined. The most important food item by weight was other fishes which accounted for 77% of the total. Other important prey items were polychaetes and crabs. It appears that the lack of cover for benthic prey and the tidal influence contributing to the influx of mobile animals may influence to some extent the diet of pinfish in this area. Plant material in the form of attached algae was also found. There is a virtual absence of seagrasses in this area, and it appears that pinfish consume algae which are epiphytic upon mangrove prop roots. Some species of algae from this area identified from pinfish stomachs are Derbesia vauchiaeformis, Derbesia lamourouxii, Enteremorpha Giffordia mitchellae, Cladophora delicatula, Polysiphonia subtillissima, Chaetomorpha gracilis, and Microcoleus lyngbyaceus. Algae of the genera Derbesia and Cladophora are commonly found associated with mangrove communities in the Tampa Bay area (Dawes, 1967). Only 8 1 fish were examined from the beach habitat. Detritus (41.53%) and polychaetes (22.08% of the total) 59


were the two major ingested items by weight. Fifty-five of the fish were less than 51 mm SL, and many important food items were too small to be weighed. Plant material, mostly Microcoleus lyngbyaceus and Schizothrix arenaria ecophene chthonoplastes, occurred in 20 of these fish. Copepods and amphipods each appeared in 19 stomachs. Habitat and Size Class Figure 14 (A-H) compares food items eaten by fish of all size ranges from each monthly station. Size class 1 and 2 fish from Station I eat mostly small crustaceans, pri-marily copepods and amphipods. Size class 3 eat detritus and plant material in greater abundance. Crustaceans are important also, making up 40% of the total weight where decapod shrimp have replaced copepods in the diet. In size class 4 pinfish amphipods and decapod shrimp account for almost 50% of the total. Detritus increases as well, while there is a considerable decrease in the amount of vegetation that is consumed. The first size class to eat plant material as the dominant food item is class 5. It accounts for 35% of the total. The amount of detritus remains about the same, while crustaceans, decapod shrimp and crabs decrease to slightly less than 22%. Plant material at 47% and detritus at 32% are the major food items for size class 6 fish. Crustaceans are eaten to a lesser extent than the previous size class while the amount of bivalve mollusks and polychaetes is greater. Plant material accounts for 60


61 Figure 14. The major food items ingested by each size class of pinfish collected from the four monthly stations. A. Size class 1 (13 to 30 mm). B. Size class 2 (31 to 50 mm) c. Size class 3 (51 to 70 mm). D. Size class 4 (71 to 90 mm) E. Size class 5 (91 to 110 mm) F. Size class 6 (111 to 130 mm). G. Size class 7 (131 to 150 mm). H. Size class 8 ( 150 mm)


f 100 95Size C lass 13-30 m m 90-I 85I 80-I >750 70z w I :::> I a 60-_, w 0:::: lL I 50w (.? 45I 40.. -z 35-w u 30-0:::: w 25Q_ 20-15-!05 0 I IT ill I n I 19 0 1 7 4


>u z w => 0 w a:: lL w <.9 ;:! z w u a:: w a.. n Size Class 31-50 mm 6 0 4 1 0


J,oo I 95Size Class 51 -70 m m 90851':7= .. .. .. . .. . . .. .. . ... 1-80-I <.9 w :5: 70 __.J 65-, i=! 6(;-I 0 55I 1-I l.J... 50-0 45-... .. w 40... ' .. I .. I .. I .. I .. 7;':"/ : -'' <.9 35<( 1z 30-w 25(.) 0:: 20w fl... 15-10-.. "" .. -'// /r .. r/ 5I 0 N n 47 10 52 53


Size Class 71-90 mm I 95 .--;7: I .: I I 70--:: 65 -::. _J 60-b5-50-!..L. 0 45 w 40-(!) z w (.) ct: w 0... 35302520.. .. .. ... .. . . . .. .. .. ... ... .. ... 1:. t : :: . . . . .


"' "' 1-I (.!) w _J ;:! 0 1-l.L. 0 w (.!) z w 0 0::: w 0... I II n 40 25 S ize Cla s s 91 -110 mm . . . . . . .. .. . . .. . ill 24 33


Size Class I !I-130 mm 1-I

co "" 1-I <.9 w :s: _J 0 1-LL 0 w <.9 z l.i.J u 25 I 0::: 20j w 0.... 15 1 10 5 I 0 L __ n I 14 Size . . . . . .. .. .. . . . . .. . . . . .. .. .. .. ... : .. . ... .. ... .. . . . .. . . II 21 Class 131-150mm _I : . ... . . . . .. . . .. . ... : . . . ... .. .. .. .. .. .. : . \'" ..... .. .. .. ; .. I r .] ill N 29 16


greater than 70% of the total weight of size class 7 fish. No other food item exceeds 6%. Only 5 fish in the largest size class were collected from Station I. Three had eaten lower chordates which accounted for 76.92% of the total weight and 4 had eaten plant matter for 18.94%. Many of the size ranges of fish collected from Station III had diets similar to those of fish collected from Station I. This is especially true for the first two size classes. A major difference which appears i n size class 3 and is true for all size classes is that detritus was never observed to be an important item in fish collected from Station III fish. Crustaceans and bivalves account for most of the food in size class 3. Bivalves are important in the next two size classes as well. Crustaceans, fish, plant material, and bivalves are important in size class 4. Vegetation becomes very important in size class 5. Crustaceans and bivalves remain at similar percentages. Plant matter increases in importance in size class 6 while bivalves decrease and crustaceans remain about the same. As in the case of fish collected from Station I, size class 7 fish from Station III eat plant material almost exclusively. It accounts for 85% of the total. Only 2 fish in size class 8 were collected From Station III. One had eaten a sea urchin which weighed almost 800 mg while the other had eaten over 300 mg o f Syringodium T h e diets o f pin fish collected from S t a tions II and IV were not as similar to each other as were those from 70


Stations I and III. For fish collected from Station II, crustaceans and bivalves were important food items for size classes 3, 4 and 5. No fish of the two smallest size classes were collected from this station. Detritus first appears as a major item in size class 5. The diet of size class 6 fish is dominated by detritus and two one-time occur-rences, crustacean larvae and mysid shrimp. Size class 7 pinfish ingested detritus almost exclusively, and the single size class 8 fish examined from Station II ate detritus as well. The occurrence of detritus in stomachs of fish from Station I V is more apparent in smaller size classes than at Station II. While crustaceans are important in the first two size classes, detritus and plant material are present as well. Pinfish collected from Station IV ingested con-siderable amounts of detritus in size classes 3 to 7. The lowest percentage of detritus in this range is 47.58% for size class 6. Detritus is eaten almost exclusively in size classes 3, 4 and 7. The other important food ite ms are plant material and polychaetes in size class 6. Only 4 fish 71 from size class 8 were collected from this station. Detritus, p lant m ateria l and polychaetes w ere the principal food items. Table 6 describes ontogenetic progressions for fish from the 4 stations.


Station I II III IV TABLE 6 Ontogenetic Progression of Food Items According to Habitat Size Range 13-50 51-90 91-130 130-170 51-90 91-130 130-170 13-50 51-90 91-130 130-170 13-50 51-90 91-130 Food Small benthic crustaceans Amphipods Decapod shrimp Vegetation Detritus Vegetation Detritus Vegetation Crustaceans Bivalves Detritus Crustacean larvae Mysids Bivalves Detritus Small crustaceans Crustaceans Bivalves Fish Vegetation Crustacean larvae Decapod shrimp Bivalves Vegetation Benthic crustaceans Nematodes Detritus Vege tation Detritus D etritus 72


Station IV TABLE 6 (cont'd.) Size Range 91-130 131-150 151-170 Food Po1ychaetes Fish Vegetation Detritus Detritus Vegetation Po1ychaetes 73


Seasonality Seasonal data from all four seasons are presented in Figure 15. Plant material and detritus were the major food items ingested in all four seasons. The amount of plant material ingested remained relatively constant within each season. The range was 38.77% in autumn to 44.08% in summer. The values for plant material were more variable being high in spring and summer and lower in autumn and winter. Autumn was the season in which the diversity of prey items was greatest. Decapod shrimp which accounted for 11.23% of the total weight was the most important food other than plant matter and detritus. Other forage items in order of importance were bivalves, lower chordates, fishes, mysids, amphipods, and colonial hydrozoans. In winter, food items other than plant material and detritus, were decapod shrimp, polychaetes, and amphipods which constituted 14.24%, 9.14%, and 6.28% of the total weight, respectively. Bivalve mollusks and crabs accounted for the remainder of the diet. During the spring plant matter (29.87%) approaches the value of detritus (40.88%). The other major food item was porcellanid crab larvae which accounted for 15.17%. In summer the ingested weight of plant matter and detritus are virtually identical with values of 43.98% and 44.08%. Decapod shrimp ranked third (4.30%). Figure 16 (A-D) shows seasonal differences within each of the four monthly habitats. 74


Figure 15. The major food items ingested by pinfish collected during the four seasons. Legend of food items in Figure 10. 75


::t: C) w 3:: _J 0 lL 0 lLI <:> z w (.) a: "' a. 0 AUTUMN WINTr::R SPRiNG SUMMER


Station I In autumn plant matter, detritus and lower chordates each account for about 25% of the total. Other food items are decapod shrimp, bivalves and amphipods. In winter the same pattern holds e xcept that amphipods increase in impor-tance in the diet while lower chordates disappear. Crabs, polychaetes, bivalves and decapod shrimp make up the rest of the diet. In the spring plant matter (greater than 67% of the total weight) is the dominant food items. Other types of food were a single sea urchin, detritus, lower chordates and amphipods. Fish collected from Station I during the summer demonstrated greater diversity in diet than the population as a whole during this season. Along with plant matter and detritus, decapod shrimp (20.49%), fish (17.92%), bivalves (7.75%), and crabs (6.33% ) make up the diet. Station II At this location, detritus is ingested in great abundance in all seasons but winter. In autumn it accounts for 75.12% of the total weight of food items. Crustaceans, primarily mysids, amphipods, and crabs, make up an additional 20.59%. In the winter bivalves make up the bulk of the diet (55.23%). Plant material (25. 78% ) and polychaetes (8.62%) are the other important items. Detritus (72.77% ) and crustacean larvae (22.75% ) account for almost the total diet in the spring. In the summer the amount of detritus ingested 77


Figure 16. The major food items ingested by pinfish collected from the four monthly stations during each of the four seasons. A. Station I B. Station II C. Station III D. Station IV 78


I-I l9 w 3: _J I 0 II lL 0 w l9 z lLl 0 0::: w 0... AUTUMN WINTER SPRING SUMMER


0 co II I-:::c (.!) LLJ 3: _j 0 1-LL. 0 w (.!) z w (_) 0::: w a.. 25 20 15 1 0 5 0--'-AUTUMN WINTER SPRING SUMMER


is greater than 90% and is the only significant food-type eaten. Station III As in Station I, but to a greater extent, plant material is important in all seasons at Station III. In autumn it accounted for 40.26% of the total. Decapod shrimp (25.32%), bivalves (14.63%), and to a lesser degree, fish and hydrozoans made up the bulk of the diet. In the winter decapod shrimp (54.26%) and plant material (29.70%) were the major food items. The importance of plant material increased to 53.05% in the spring. Crustacean larvae (25.58%) and decapod (7.74%) were the other significant food items. In the summer, pinfish collected from this station had eaten plant material almost exclusively. It accounted for 86.75% of the total. The next most important food item was decapod shrimp (4.89%). Station IV Detritus was extremely important in all four seasons. The lowest value was 63.30% in autumn. Plant material, decapod shrimp, and fish made up the remainder of the diet in this season. During winter, detritus accounted for 75.80% of the total. Polychaetes and plant material were the only other important food items. During the spring the value for detritus was 70.57%. Plant material, fish, polychaetes, and amphipods were the other food items. During the summer fish collected from this station were found to 81


N co m 1-I LL.J _, ;:! 0 1-LL 0 w ;:! z w u w CL 95 9085 80 75 70 45 35 30 AUTUMN WINTER SPRING SUMMER


II <.9 w 50 5u 45 w 40 LL 0 35] z 30 25 f5 20 a... . .. .. . .. .. .. . . .. . . AUTUMN ... .. .. . ... ... . . . . . WINTER . :.1 .. ... .. .. . .. .. SPRING .. . .. . :I . . . . ... .. . . : . .. .. .. .. . . . I


have recently fed almost exclusively on detritus which accounted for 94.79% of the total weight. 84


DISCUSSION The pinfish is an opportunistic omnivore as evidenced by the numerous different food items it ingests. The data for those fish collected at Anclote indicated the ingestion of a wide variety of mostly benthic items; the most common of which was plant material (primarily sea-grasses), detritus and crustaceans. The information that pinfish are capable o f utilizing numerous resources has long been understood and is well-documented (Linton, 1904; Smith, 1907; Hildebrand and Schroeder, 1928; Reid, 1954; Caldwell, 1957; Darnell, 1958; Hansen, 1969; Adams, 1972; Carr and Adams, 1973). What has been of less interest to researchers are the factors involved in variation of diet of this species. Several have studied some aspect of this variation (Adams, 1972; Hansen, 1969; Darnell, 1958). For the most part, however, the majority of papers contained little quantitative or comparative data for the reason that feeding was usually a secondary component of the author's research. The three main sources of variation are ontogenetic growth, habitat, and seasonality. Most comparative work has been done with respect to ontoge n etic changes (Adams, 1972; Darnell, 1958; Carr and Adams, 1973) while few discussions of 85


the effect of habitat or seasonal variation are found in the literature. It is evident that an ontogenetic progression for pinfish at Anclote could not be discussed without taking into account habitat variation. The one thing that pinfish from all stations have in common is the ingestion of copepods and amphipods by the two smallest size classes. Fish greater than 50 mm in all but Station IV eat larger crustaceans until the beginning of size class 5. At this point and depending upon the habitat, plant material or detritus becomes the dominant food item. Habitat is a very important factor influencing the pinfish diet. Examination of stomachs from fish collected from the four monthly stations reflected the general avail-ability of resources in each habitat. Data from the two grass areas (Stations I and III) revealed tha t pinfish w ere not only consuming the resident seagrass, Syringodium filiforme, but were feeding upon algal epiphytes of the seagrass, fish, and benthic invertebrates associated with the grass bed. Station II was an area of sparse vegetation and apparent low abundance o f animal p rey. The item found in the majority of stomachs was detritus. Ontogenetic v a riation was less apparent for fish collected at this station. There were possibly two reasons for this; the first being t h e l ow amount o f available resour c es, and t h e second being the low abundance o r total absence of the two smallest size 86


classes. Station IV was an interesting area. It was intermediate in vegetation between the two Syringodium stations and the sand station and located in an area of a turtle grass bed. The leaves died off in the colder months, and the plants did not extensively refoliate until the late spring or early summer. The data indicated that most fish of all size ranges had ingested detritus in spite of the seasonal abundance of seagrass. Benthic invertebrates and some plant matter, primarily benthic algae, were eaten as well. The seagrass, Thalassia testudinum, was rarely eaten. When it did occur in a stomach, there was never a large amount of it, only small fragments. The more seasonal character of this seagrass bed may perhaps lower the diversity of benthic invertebrates. Unfortunately, at this time, there is no data available to compare invertebrate densities among the four stations. The exclusion from the diet o f Thalassia and the less abundant ingestion of benthic invertebrate s could possibly b e the reasons for the high amount of ingested detritus at this station. Pinfish from Anclote exhibit changes in d iet due to habitat in such a m arked way that it camouflages much o f the variation due to other factors such as ontogeny and season. The bayou collection is a good example since all fish examine d had contained fishes. Thi s demonstrated that small a n d large pinfish all utilized a r eadily a vail a ble food source despite general ontogenetic feeding habit 87


variation. Seasonal changes show that pinfish at Anclote eat mainly plant material and detritus in all seasons with the highest percentages being eaten in the warmer months. There is greater diversity of food items ingested in autumn and winter. During the fall and winter, the leaves of seagrasses tend to die off and are replaced by benthic algae as the most dominant vegetation. Physically, benthic algae are less dense than seagrass leaves and would not weigh the same as an equal volume of seagrass. Also, the factors that determine algal succession may not be as uniform as those that provide for the new growth of seagrass leaves, and it is conceivable that at certain times during the colder months little vegetation may be available to the pinfish. Another e xplanation as to why less plant material is eaten in the colder months is apparent when the seasonal size-frequency of pinfish is considered. Large pinfish leave the estuar y to spa wn in d eeper waters i n late summer and early autumn. Bean (1903) was the first to document this m igration. Since that time it has been mentioned by Hildebrand and Schroeder (1927), Hildebrand and Cable (1938), Hildebrand (1955), Caldwell (1957), and Hansen (1969). In addition, small pinfish can remain in a shallow estuar y because they are more able t o withstand temperature extre mes than larger ones ( Wohlschlag e t al. 1968). Cameron (1969) suggests that "since the movements of larger 88


fish into deeper waters occur at times of actual or potential temperature stress, such movements may be related to the relative ability of large and small fish to meet the extra metabolic demands necessary to cope with such stress." In any event, movement is due to whether spawning alone or in conjunction with temperature, the majority of large pinfish are absent from the estuary in the late fall and in winter. The pinfish that remain are, for the most part, year class 1 and 2 fish. Some larger fish are present also. The juvenile pinfish are more carnivorous in their habits and the greater amount of animal matter in the diet is apparent in the data for autumn and winter. Plant material and detritus values would still be high because those fish at this time that do ingest these items are usually large and normally concentrate on these food sources. In addi-tion, detritus and vegetation would account for a substantial percentage of the total due to two factors. First of all, the easy accessibility of these two items would provide the pinfish with a supply of ingestible material in unlimited quantities without the fish having to search for it. Secondly, the density of detritus and possibly benthic algae exceeds that of animal items which in the case of crustaceans were highly digested save for the exoskeleton. Post-larval pinfish appear in late winter and early spring. It is not until the late spring and summer that large pinfish, whether through recruitment, growth, or return 89


of spawning individuals, become plentiful. For the most part the four-station data were fairly predictable. In the grass stations vegetation was the dominant item year round as was detritus in the other two but there were exceptions to these general patterns. At Station I plant material was extremely abundant only during the spring. In every other season animal food, primarily crustaceans, and detritus had values only slightly less than vegetation. At Station II in the winter, only 12 fish were collected. Examination of the stomachs revealed that detritus was a negligible item. larger tha n 111 mm SL. Only 1 fish of the 12 was The study by Hansen (1969) was the only one encountered that considered seasonality an important variable. according to season are presented in Table 7. His data The pinfish has been described as a grazer by several authors (Gunter, 1945; Caldwell, 1957) primarily because of the large amount of vegeta t ion and detritus found in the stomachs. T h e capture o f pre y such as crustaceans, fish, polychaetes, and mollusks is in a large part dependent upon this benthic mode o f feeding. However, the present paper has shown t h a t pinfish are capable of switching from the grazing habit to a more planktonic one when an easily accessible planktonic food source is present. The presence of the porcellanid crab l a r vae at Stations II and III d emonstrated this. Not o n l y were pinfish from those areas feeding almost e xclusively in the 90


Seasonal Season Autumn Winter Spring Summer TABLE 7 Comparisons of Food Items By Pinfish Collected From Pensacola Bay, Florida (After Hansen 1969) 76 mm Vegetation Crustaceans Crustaceans Polychaetes Chordates Crustaceans Polychaetes Sand Vegetation Ingested /:76-173 mm Vegetation Sand Chordates Crustaceans Vegetation Polychaetes Sand Vegetation Chordates Vegetation Sand 91

PAGE 100

upper water column, but the planktonic mass attracted large numbers of pinfish from other areas in the estuary. This was an example of how the pinfish population was provided with an easily accessible and potentially high nutritional food source and demonstrated that it was capable of taking advantage of this opportunity. It is not meant to imply that pinfish are capable of selecting food items as desirable on the basis of energy utilization. Their feeding behavior indicates that they take advantage of the resources associated with the habitat in which they find themselves. Station II is an area where available resources are low. Plant material, in the form of benthic algae, is present only at certain times of the year. Areas of sparse vegetation are also characterized by 92 lowered diversity of benthic invertebrates. This has been described for an area in Tampa Bay by Blake et al. (in press). Very little nutritional energy is to be gained in areas such as this, but this is by no means a long-term situation. Pin-fish are not permanently bound to this area and are capable of moving to areas of abundant vegetation and prey organisms. In richer habitats they have a choice of more items which are readily available. In habitats such as these, especially during times of high productivity, variation in diet due to ontogenetic changes is more apparent.

PAGE 101

CONCLUSION The present study has substantiated the view that pinfish feed upon a wide variety of food items. At least 15 different food items were taken in considerable abundance. The most important of which were crustaceans, detritus and plant material. Crustaceans make up the bulk of the diet of post-larval and juvenile pinfish. Pinfish begin life in the estuary by consuming small crustaceans, mainly copepods and small amphipods. Larger juveniles ingest larger amphipods, decapod shrimp and crabs. Although adults consume other items in favor of crustaceans, it was not rare to find large snapping shrimp or crabs in stomachs of larger pinfish. The number of pinfish that ingested detritus was second only to the number that ingested plant material; however, the nutritional value of detritus is questionable. Odum (1971) and Darnell (1958) emphasize the importance of detritus-based food chains. Both authors refer to organisms that benefit directly from ingesting detritus. Among these are many lower benthic invertebrates and several species of fishes, most notably mullet (Mugil and menhaden (Brevoortia spp.). Since the detritus found in pinfish 93

PAGE 102

stomachs contained mostly sand (greater than 90% by weight; Robert Fisher, personal communication), the gain in energy must have been minimal. Moreover, the pinfish is not endowed with alimentary modifications such as the mullet gizzard which would enable it to utilize this source efficiently. In every pinfish stomach in which there was a considerable amount of detritus, a much greater amount was found in the intestine ready to be eliminated. It appears that any nutri-tion to be gained from eating detritus would come from living organisms (diatoms, epiphytic algae, nematodes, copepods, crustacean larvae) and decaying organic matter (including saprophyti c bacteria). A large quantity would have to be ingested to provide it. The role of plant material in pinfish diet has been well documented; however, the question of nutritive importance has been raised also. Darnell (1958) doubts the energetic value of algae although filamentous algae made up 40.3% and 34.5% of the total food volume from his two largest size classes. Caldwell (1957) describes the pinfish as being "catholic" in its food habits with small crustaceans making up the bulk of the diet and plant material being an incidental item. Springer and Woodburn (1960) question Caldwell's evaluation and note that 11 of 57 stomachs examined contained substantial amounts of shoal grass, Diplanthera wrightii, and the gree n alga, Enteromorpha Othe r authors (Hildebrand and Schroeder, 1927; Gunter, 1945; Reid, 1954; Adams, 1972; and Carr and Adams, 1973) 94

PAGE 103

mention the abundance of vegetation that was found in stomachs. Like detritus, vegetation is found in abundance, but unlike detritus, there appears to be considerable support for the beneficial nature of this food item. No previous author other than Caldwell has questioned the nutritive value of seagrasses, and this would seem to be the most highly controversial aspect of pinfish vegetative habits. A plant such as manatee grass, Syringodium filiforme, contains a good portion of its bulk as undigestible cellulose. Like detritus, fish in whose stomachs were found great amounts of Syringodium also had large amounts in the intestine. Much of the seagrass, however, in the posterior portion of the stomach appeared to be well digested indicating that pinfish may ingest and eliminate items more rapidly than the digestive processes can act. There appears to be a considerable amount being ingested. The hypothesis that algae are taken in only incidentally is not supported by the present study. Many times benthic algae were found in stomachs in which there was no evidence of any crustaceans or other small animals which would have been considered the primary prey items. The recognition that pinfish can be herbivorous is important in showing that the population as a whole or a single individual can occupy different trophic levels. 95

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SUMMARY The stomachs of 808 pinfish collected from the Anclote Anchorage were examined. Variation in diet was apparent and was influenced by three major factors: fish size, habitat and season. Pinfish were separated into eight size classes. Com-parisons among the different size classes indicated that crustaceans were the major food of post-larval and small juvenile pinfish. Larger juveniles (greater than 90 mm) consumed larger crustaceans, bivalve mollusks, some plant material and detritus. material or detritus. Adult fish primarily ingested plant Habitat was an important variable. The study concen-trated on four stations which were sampled monthly although two other habitats were examined as well. The four monthly stations consisted of two manatee grass areas, a deep sand area, and a mixed sand-grass area in which the major seagrass, Thalassia testudinum, was abundant only in fue warmer months of the year. Fish collected from the two manatee grass stations had consumed primarily seagrasses, benthic algae, and benthic invertebrates. Detritus was the major item ingested at both the deep sand station and the mixed station even though there was a seasonal seagrass bed at 96

PAGE 105

the latter. Pinfish also exhibited seasonal variation in diet. Seasonal comparisons of data from the four monthly stations were examined. There was a considerable difference in food habits at each station. Two major factors concerning this variation appeared to be seasonal changes in length frequency of the population and the general presence of available food items during the year. The data presented in this thesis supported the contention that pinfish were opportunistic feeders and were capable of taking advantage of many different resources. 97

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LITERATURE CITED Adams, C. A. 1972. Food habits of juvenile pinfish (Lagodon rhomboides), silver perch (Bairdiella chrysura), and spotted seatrout (Cynoscion nebulosus) of the estuarine zone near Crystal River, Floriaa. Master's Thesis Univ. Fla. Gainesville 146 pp. Baird, R. C., W. A. Fable, B. D. Causey, R. A. Dietz, A. Feinstein, D. M. Milliken, and J. K. Rolfes. 1973. The fish fauna of a salt marsh bayou on the gulf coast of Florida. In: Anclote Environm. Proj. Rept. 1972: 145-187. Baird, R. C., K. Rolfes, B. Causey, W. Fable, A. Feinstein, and D. Milliken, 1972. Fish. In: Anclote Environm. Proj. Rept. 1971: 176-199. Ballantine, D. 1. and H. J. Humm 1972. Benthic algae of the Anclote estuary. In: Anclote Environm. Proj. Rept. 1971: 94-122. Bean, T. H. 1903. Catalogue of the fishes of New York. New York St. Mus. Bull., 60 Zool. 9, 1903 784 pp. Blake, N. J., 1. J. Doyle, and T. E. Pyle. In Press. The benthic community of a thermally altered area of Tampa Bay, Florida. In: Proc. 2nd Ann. Thermal Ecology Symp. Augusta April 1-5, 1975. Breder, C. M. 1927. eastern Panama. 3: 91-176. The fishes of Rio Chucunaque drainage, Bull. Amer. Mus. Nat. Hist., 57 art. B d C M 1962 Interaction between the fishes Mugil re e r, . and Lagodon. Capeia, 1962: 662-663. Caldwell, D. K. 1957. The biology and systematics of the pinfish, Lagodon rhomboides (Linnaeus). Bull. Fla. St. Mus. Biol. Sci., 77-173. C J N 1969. Growth, respiratory metabolism, and ameron, . seasonal distribution of juvenile pinfish (Lagodon rhomboides Linnaeus) in Redfish Bay, Texas. Contr. Mar. Sci. Univ. Tex., l:,i: 19-36. 98

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Carr, W. E. S. and C. A. Adams, 1973. Food habits of juvenile marine fishes occupying seagrass beds in the estuarine zone near Crystal River, Florida. Trans. Amer. Fish. Soc., 102(3): 511-540. Darnell, R. M. 1958. Food habits of fishes and larger invertebrates of Lake Pontchartrain, Louisiana, an estuarine community. Inst. Mar. 353-416. Darnell, R. M. 1961. Trophic spectrum of an estuarine community, based on studies of Lake Pontchartrain, Louisiana. Ecology, 553-568. Dawes. C. J. 1967. Marine algae in the vicinity of Tampa USF Contr. #27 Dept. Bot. Bacteriol.: Bay, Florida. 1-105. Diener, R. A., A. Inglis, and G. B. Adams, 1974. Stomach contents of fishes from Clear Lake and tributary waters, a Texas estuarine area. Contr. Mar. Sci. Univ. 7-17. Fryer, G., P. H Greenwood, and E Trewavas, 1955. Scale eating habits of African cichlid fishes. Nature, 175(4468): 1089-1090. Gery, J. 1964. Poissons nouveaux ou non de l'ilha do Bananal. Vie et Mileu, suppl. 17 (Volume Jubiliare Georges Petit): 447-471. Gunter, G. 1945. Studies on the marine fishes of Texas. Publ. Inst. Mar. Sci. Univ. Tex., l(l): 9-190. Hansen, D. J. 1969. Food, growth, migration, reproduction, and abundance of pinfish, Lagodon rhomboides, and Atlantic croaker, Micropogon undulatus, near Pensacola, Florida. Fish. Bull., 135-146. Hildebrand, H. H. 1955. A study of the fauna of the pink shrimp (Penaeus duorarum Burkenroad) grounds in the Gulf of Campeche. Publ. Inst. Mar. Sci. Univ. Tex., i(L): 170-232. Hildebrand, s. F. and L E. Cable, 1938. Further notes on the development and life history of some teleosts at Beaufort, N.E. Bull. U.S. Bur. Fish., no. 24: 505642. Hildebrand, s. F. and W. C. Schroeder. 1928. The fishes of Chesapeake Bay. Bull. U.S. Bur. Fish., 43 (Part 1): 1 -366. 99

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Roese, H. D. 1966. Ectoparasitism by juvenile sea catfish, Galeichthys felis. 1966: 880-881. Hubbs, C. L. and K. F. Lagler, 1958. Fishes of the Great Lakes region. Cranbrook Inst. Sci. Bull., No. 26: 1-213. Hynes, H. B. N. 1950. The food of freshwater sticklebacks (Gasterosteus aculeatus and Pygosteus pungitius) with a review of methods used in the studies of the food of fishes. J. Anim. Ecol 19: 35-58. ., Jacobs, J. 1961. Laboratory cultivation of the marine copepod Pseudodiaptomus coronatus Williams. Limnol. Oceanolog., 443-446. Kner, R. 1860. Zur Familie der Characinen. II. Denkschriften der mathematisch-naturwissenschlaftlichen Classe der Kaiserlichen. Akademie der Wissenschaften, Wien, 9-62. Linton, E. 1904. Carolina. Parasites of fishes of Beaufort, North Bull. U.S. Bur. 321-428. Major, P. F. 1973. Scale feeding behavior of the leatherjacket, Scomberoides Lysan and two species of the genus Oligoplites (Pisces: Carangidae). Copeia, 1973(1): 151-154. Marlier, G. and N. Lelup. 1954. A curious econological "niche" among the fishes of Lake Tanganyika. Nature, 174: 935-936. Odum, W. E. 1971. Pathways of energy flow in a south Florida estuary. Sea Grant Tech. Bull., #7: 1-159. Reid, G. K. 1954. An ecological study of the Gulf of Mexico fishes in the vicinity of Cedar Key, Florida. Bull.Mar. Sci. Gulf Carib., 1-94. Roberts, T. R. 1970. Scale-eating American characoid fishes with special reference to Probolodus heterostomus. Proc. Calif. Acad. Sci., XXXVIII(20): 383390 Roberts, T. R. 1973. The glandulocaudine characid fishes of the Guayas Basin, Western Ecuador. Bull. Mus. Camp. Zool, 144(8): 489-514. Rolfes, J. K. 1974. Patterns of diversity and density in the ichthyofauna of the Anclote Anchorage, Florida. Master's Thesis Univ. So. Fla. Tampa 70 PP 100

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Rolfes, J. K., A. Feinstein, R. A. Dietz, D. M. Milliken, R. C. Baird, W. A. Fable and B. D. Causey. 1974. Ecological base-line study of the fish of the Anclote Anchorage. In: Thermal Ecology, R. R. Sharitz and J. W. Gibbons (eds.): 448-461. Smith, H. 1907. The fishes of North Carolina. N. Car. Geol. Surv., l: 114-117. Springer, V. G. and K. D. Woodburn. 1960. study of the fishes of the Tampa Bay Bd. Cons. Pap. Ser., No. 1: 1-104. An ecological area. Fla. St. Wohlschlag, D. E. J. N. Cameron and J. J. Cech. 1968. Seasonal changes in the respiratory metabolism of the pinfish (Lagodon rhomboides). Contr. Mar. Sci. Univ. Tex., 13: 89-104. 101


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