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Sound production and behavior of red grouper (_epinephelus morio_) on the west florida shelf


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Sound production and behavior of red grouper (_epinephelus morio_) on the west florida shelf
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Montie, Misty
University of South Florida
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Tampa, Fla
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Passive acoustics
Diel periodicity
Acoustic communication
Fish sounds
Dissertations, Academic -- Marine Science -- Masters -- USF   ( lcsh )
non-fiction   ( marcgt )


ABSTRACT: Passive acoustic and digital video recordings were used to investigate sonic activity and behavior of red grouper (Epinephelus morio) on the West Florida Shelf. Red grouper were found to produce a unique series of low-frequency (180 Hz peak) pulses, consisting of 1-4 brief (0.15s) broadband pulses and a 0.5-2s down-swept "buzz" (i.e., short call); occasionally these were followed by a rapid series of 10-50 broadband pulses (i.e., pulse train). Sound production was observed throughout the day and night, but most sounds occurred between sunrise and sunset, with a noticeable increase during late afternoon. Behaviors associated with sound production included territorial displays and courtship interactions, indicating that sound production is likely related to spawning activity. Thus, monitoring red grouper using passive acoustics could be an effective tool in fisheries management and conservation efforts.
Thesis (MS)--University of South Florida, 2010.
Includes bibliographical references.
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by Misty Montie.
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Sound production and behavior of red grouper (_epinephelus morio_) on the west florida shelf
h [electronic resource] /
by Misty Montie.
[Tampa, Fla] :
b University of South Florida,
Title from PDF of title page.
Document formatted into pages; contains X pages.
Thesis (MS)--University of South Florida, 2010.
Includes bibliographical references.
Text (Electronic thesis) in PDF format.
Mode of access: World Wide Web.
System requirements: World Wide Web browser and PDF reader.
3 520
ABSTRACT: Passive acoustic and digital video recordings were used to investigate sonic activity and behavior of red grouper (Epinephelus morio) on the West Florida Shelf. Red grouper were found to produce a unique series of low-frequency (180 Hz peak) pulses, consisting of 1-4 brief (0.15s) broadband pulses and a 0.5-2s down-swept "buzz" (i.e., short call); occasionally these were followed by a rapid series of 10-50 broadband pulses (i.e., pulse train). Sound production was observed throughout the day and night, but most sounds occurred between sunrise and sunset, with a noticeable increase during late afternoon. Behaviors associated with sound production included territorial displays and courtship interactions, indicating that sound production is likely related to spawning activity. Thus, monitoring red grouper using passive acoustics could be an effective tool in fisheries management and conservation efforts.
Advisor: David A. Mann, Ph.D.
Passive acoustics
Diel periodicity
Acoustic communication
Fish sounds
Dissertations, Academic
x Marine Science
t USF Electronic Theses and Dissertations.
4 856


Sound Production and Behavior of Red Grouper ( Epinephelus morio ) on the West Florida Shelf by Misty D. Montie A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science College of Marine Science Universit y of South Florida Major Professor: David A. Mann, Ph.D. Christopher C. Koenig, Ph.D. Ernst B. Peebles, Ph.D. Date of Approval: May 5, 2010 Key words: p assive acoustics, diel periodicity, acoustic communication, Epinephelidae fish sounds Copyri ght 2010, Misty D. Montie


DEDICATION I would like to dedicate this thesis t o my mom, Roberta Cauthron, for her unwavering support and encouragement, and for taking the t ime to look up all the words she know. To Gay Allison, for her absolute fait h in me, and for always being a mother, even though she To my husband and best friend, Eric Montie, whose never ending enthusiasm and scientific curiosity made it impossible to be anything but excited about my research. And finally, to my dad, Eric Nelson, for sharing his love of science and fascination with nature and for being the greatest father a girl could have


ACKNOWLEDGEMENTS I would like to thank the officers and crew of the M / V Liberty Star, the N a tional Undersea Research Cent er ROV pilots Lance Horn and Glen Taylor and divers Doug Kesling, Scott Fowler, Thor Dunmire and Kerry Dillon I would also like to thank Dr. Felicia Coleman, Dr. Chris Koenig, Peter Simard and Carrie Wall for assistance in the lab and field as well as Dr. Eric Montie for advice, assistance and support This research was made with Government support under and awarded by DoD, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a awarde d to MDM and the National Undersea Research Center at the University of North Carolina at Wilmington, NOAA Grant #NA030AR4300088.


i TABLE OF CONTENTS LIST OF TABLES ii LIST OF FIGURES iii ABSTRACT iv INTRODUCTION 1 MATERIALS AND METHODS Study Si tes 6 Video a nd Acoustic Recorders 7 Analysis of Sounds 8 Behavioral Analysis 10 Periodicity Analysis 11 RESULTS Description of Sounds 12 Behavior 13 Diel Periodicity 14 DISCUSSION 15 LITERATURE CITED 35 ABOUT THE AUTHOR END PAGE


ii LIST O F TABLES Table 1 Location, deployment, and data collection information for all recorders. 20 Table 2 Descriptive stat istics for red grouper calls. 21 Table 3 Sound properties and obser ved behaviors of red grouper. 22


iii LIST OF FIGURES Figure 1 Locations of marine reserves on West Florida Shelf where acoustic and v ideo recorders were deployed. 23 Figure 2 Diagram of DSG audio record er setup in the water column. 24 Figure 3 (A) Waveform, (B) spectrogram (FFT = 2048 samples) and (C) band sou nd pressure level (BSPL; frequency resolution = 10 Hz) of a ty pical red grouper short call. 25 Figure 4 (A) Waveform, (B) spectrogram (FFT = 2048 samples) and (C) band sound pressure level (BSPL ; frequency resolution = 10 Hz) of a red grouper call with a pulse train. 26 Figure 5 Average fast Fourier transform (FFT) f or red grouper calls (n=116). 27 Figure 6 Distribution of peak frequ ency values for all red grouper c alls (n=116). 28 Figure 7 Distribution of 6 dB bandwidth f or red grouper calls (n=116 ). 29 Figure 8 Received levels (root mean s quare; dB relative to reference pressure of 1 Pa) of red grouper calls (n=116). 30 Figure 9 Number of pulses in red grouper calls versus total call duration (n=116). 31 Figure 10 Time series of red grouper sound pr oduction at Steamboat Lumps and Madison Swanson Mar ine Reserves, May 7 14, 2008. 32 Figure 11 Diel periodicity of red grouper sound production at Steamboat Lumps and Mad ison Swanson Marine Reserves. 33 Figure 12 Periodicity of red grouper sound production by call type at (A) Steamboat L umps and (B) Madison Swanson. 34


iv Sound P roduction and Behavior of Red Grouper ( Epinephelus morio ) on the West Florida Shelf Misty D. Montie ABSTRACT Red grouper ( Epinephelus morio ) are long lived, commercially important, soniferous fish belonging to the family Epinephelidae Found throughout the western North Atlantic and Gulf of Mexico, they are protogynous hermaphrodites, and peak spawning occurs from March through May. Unlike many grouper species, red grouper do not form large spawning aggregations; rather, they form small polygynous grou ps, and remain in relatively close proximity to rocky depressions excavated in the sandy bottom by males. This excavation activity creates structure and habitat for a wide variety of species, and as a result, red grouper are a keystone species on the West Florida Shelf. While extensive life history information exists, largely from fishery catches, little is known about sound production or behavior of red grouper in their natural environment. Passive acoustic recordings combined with simultaneous digital video recordings were used to investigate sonic activity and behavior of red grouper on the Steam boat Lumps and Madison Swanson marine r eserves on the West Florida Shelf. Red grouper were found to produce a unique series of low frequency (180 Hz peak) pul ses, consisting of 1 4 brief (0.15 s) broadband pulses and a 0.5 2 s down (i.e., short call) ; occasionally these were followed by a rapid series of 10 50 broadband pulses (i.e., pulse


v train) Sound production was observed throughout the day a nd night, but most sounds occurred between sunrise and sunset, with a noticeable increase during late afternoon. Behaviors associated with sound production included territorial displays and courtship interactions, indicating that sound production is likel y related to spawning activity Thus, monitoring red grouper using passive acoustics could be an effective tool in fisheries management and conservation efforts.


1 INTRODUCTION Red grouper ( Epinephelus morio ) are long lived, commercially important members of the family Epinephelidae and are found throughout the western Nort h Atlantic and Gulf of Mexico. Recent evidence indicates that red grouper modify their local environment by excavating sediments to expose rocky depressions on the seafloor (Coleman et al. 2010) wide variety of species and re d grouper may serve as keystone species in the Gulf of Mexico (Coleman and Williams, 2002; Coleman et al. 2010) Despite their economic and ecological significance, little is known about the in situ behavior of red grouper. The bulk of information available is based largely on sample s colle cted from or dependent on fishery catches captive individuals or assumptions extrapolated from closely related species Red grouper in the United States are managed as part of the shallow water grouper (SWG) complex, which also includes gag ( Mycteroperca m icrolepis ) black ( M. bonaci ) yellowmouth ( M. interstitialis ) and yellowfin grouper ( M. venenosa ) red hind ( E. guttatus ) rock hind ( E. adscensionis ) and scamp ( M. phenax ) (SEDAR, 2006) South Atlantic and Gulf of Mexico populations are geographic ally isolated, and are managed as separate stocks (Burgos et al. 2007) In 2008, t he National Marine Fisheries Service repo rted commercial red grouper landings of 5,578,037 pounds (2,530,200 kg) for the west coast of Florida alone, which were worth $13,459,803 This catch compo s ed


2 80% of the United States Gulf of Mexico grouper fishery (NMFS, 2010) Starting i n 2008, several regulatory changes were implemented to reduce overfishing of gag grouper T hese changes were offset by reg ulations aimed at increasing harvest of red grouper, which includ ed : i) increasing the annual red grouper total allowable catch by 15%, from 6.56 million pounds (mp; 2,975,600 kg) to 7.57 mp (3,433,700 kg) gutted weight, ii) establishing a seasonal SWG fis hery closure from February through March, aimed at reducing gag harvest by 26%, while increa sing red grouper harvest by 17%, and iii) lowering the minimum size limit for red grouper from 20 inches (50.8 cm) to 18 inches (45.7 cm) total length (GMFMC, 2008) While current assessments indic ate that the Gulf of Mexico red grouper stock is neither overfished nor undergoing overfishing, overfishing has occurred as recently as 2004 (SEDAR, 2006) and a red tide mortality event in 2005 likely resulted in a subsequent population decrease (SEDAR, 2009a) The South Atlantic stock was overfished and overfishing was occurring in 2009 (SEDAR, 2009b) Responsible harvesting and effective management are essential to the long term sustaina bility of any fishery. Specifically, reducing fishing pressure on reproductively active individuals will support successful spawning and facilitate strong recruitment to the population. Exploring new methods of monitoring habitat use and rep roductive act ivity are important factors in developing these regulations. Like many epinephelids, red grouper are protogynous hermaphrodites; female to male transition occurs between 5 10 years of age, at an annual transition rate of approximately 15% (Jory and Iversen, 1989) The red grouper reproductive season extends from J anuary through July, with a peak in spawning activity occurring between


3 March and May (Moe, 1969; J ohnson et al. 1998; Collins et al. 2002; Burgos et al. 2007) Limited findings suggest that, unlike many grouper species, red grouper do not form large spawning aggregations (Brule et al. 1999) ; rather, they form small polygynous groups (Coleman et al. 1996) and remain in relatively close proximity to limestone outcroppings or rocky depressions excavate d in the sandy bottom by males (Moe, 1969; Bullo ck and Smith, 1991; Coleman and Williams, 2002; Scanlon et al. 2005; Coleman et al. 2010) Red grouper spawning behavior is believed to be similar to that of coney ( Cephalopholis fulva ) and graysby ( C cruentatus ) which has been described as nonmigrat ory, polygynous pair spawning (Sadovy et al. 1994; Coleman et al. 1996) Male coney (Family: Epinephelidae) are territorial, and spawning with multiple females occurs daily, just prior to sunset (Heemstra and Randall, 1993) D etails of red grouper spawning behavior, however, remain largely unknown Red grouper larvae are pelagic, and juveniles can be found on near shore re efs grass beds and estuaries (Moe, 1969; Burgos et al. 2007) With the onset of sexual maturity, typically around 5 years of age, individ uals migrate into deeper waters of the continental shelf and shelf edge (Moe, 1966; 196 9) Adults are not thought to undertake long distance seasonal migrations T agging studies have shown that 87% of individuals remained within 10 miles of the tagging location, and 61% remained within one mile (SEDAR, 2006) Given that red grouper d istribution appears to be relatively stable, large scale mapping throughout the Gulf of Mexico would provide valuable information to fishery managers. Red grouper are soniferous, and passive acoustic recordings would be a cost effective way to perform thi s mapping.


4 The mechanism of r ed grouper sound production is believ ed to be similar to the closely related Nassau grouper, E. striatus and results from rapid contraction of bilateral mus cles behind the opercles, which causes the sw im bladder to vibrate (Hazlett and Winn, 1962) Fish and Mowbray (1970) describe a simple boom sound generated during competitive feed ing among several captive adult re d grouper. T hey also describe s ounds of numerous other epinephelid fishes, including Nassau grouper, rock hind, red hind, speckled hind ( E. drummondhayi ), Warsaw grouper ( E. nigritus ), and goliath grouper ( E. itijara ). Low frequency booms, thumps, knocks rasps and grunts were observed H owever, most observations were made by mechanical or electrical stimulation of captive individuals, which provide s little insight into the full repertoire of possible sounds or the associated behaviors Fishes pro duce s ounds in a variety of contexts, including territorial defense (Ladich, 1997) courtship (Myrberg et al. 1986; M cKibben and Bass, 1998) and spawning (Lobel, 1992; Mann et al. 1997; Amorim et a l. 2003) but very few published reports identify the specific in situ behavior associated with sound production Several studies in the 1960s utilized underwater acoustic video recorders to observe sound production in fishes, primarily to identify spec ies specific sounds (Steinberg et al. 1965; Myrberg, 1973) Laboratory studies have used video to observe sound production and behavior in captive fish (McKibben and Bass, 1998; Malavasi et al. 2009; Maruska and Mensinger, 2009) Commercially available d igital recorders, microcomputers and high capacity data storage devices have greatly expanded the potential applications of this technology. This study used p assive acoustic recordings


5 combined with simultaneous digital video recordings to explore the behavior of red grouper in their natural environment, focusing on sound production and its potential relationship to spawning. Primary objectives we re to 1 ) describe sounds produced by red grouper in situ 2) relate sound production to specific behaviors and 3 ) describe the daily periodicity of red grouper sound produc tion.


6 MATERIALS AND METHODS Study Sites Recorders were deployed within the Madis on Swanson (MS) and Steamboat Lumps (SL) marine r eserves on the West Florida Shelf (Figure 1) These reserves were established in 2000 and are closed year round to all commercial and recreational reef fishing (GMFMC, 2003) While the reserves were implemented primarily to reduce fishing pressure on aggregations of gag and scamp (Coleman et al. 2004) red grouper also occur within reserve bo undaries (Scanlon et al. 2005) In MS, red grouper are commonly associated with low relief carbonate rock outcroppings in the sandy bottom; in SL red grouper are typically fou nd in exc avated solution holes, which can be observed in high resolution sidescan sonar images (Coleman et al. 2010) Field operations were carried out aboard the M/V Li berty Star from May 5 15, 2008. S idescan bathymetry maps were used to guide the ship to areas likely to have red grouper. A Deep Ocean Engineering Phantom S2 remo tely operated vehicle (ROV) was used to provide real time video tran smission to the control ship, allowing for verification of red grouper presence This initial assessment enabled placement of recor ders close to fish in water depths of up to 90 meters (T able 1)


7 Video a nd Acoustic Recorders Autonomou s record ers captured digital video using low light, wide angle black and white cameras. Custom cylindrical PVC housings with a clear acrylic plate covering one end were mounted on aluminum tripods weighted with lead. Four housings contained Chasecam PDR100 Solid State Digital Recorders (Chase Product Development, Inc., La Mesa, CA) with 4 internal Lithium AA batteries, while the fifth contained an Archos 605 WIFI Portable Media Player (Archos Inc., Greenwo od Village, CO). Additionally, each unit had an SSC 108WXXB .0003 Lux Low Light B/W 420 Line Board Lens camera (Advance Security Products, Bellevill e, IL) mounted to the acrylic plate. Two High Tech, Inc. HTI 96 MIN Series hydrophones ( Gulfport, MS ; sens itivity = 164 1 ; flat response between 2 Hz 37 kHz ) were also connected to each video housing unit, one directly attached to the back plate, and the second attached to a 1.4 m tether. The two channels of audio were recorded continuously at a sample rate of 44.1 kHz, and along with video data, were saved to A Data Speedy 32 GB compact flash memory cards (A DATA Technology Co., Ltd., City of Industry, CA), except in the case of the Archos recorder, which had 30 GB internal memory. Each unit was powered by 8 D cell batteries connected in series F oam padding was packed into each housing prior to sealing to prevent equipment movement or damage S ilica packs were used to absorb moisture and prevent condensation from interfering with the video. Video recorders were placed manually by deep sea scuba divers around active red grouper holes (i.e. holes observed by the ROV to have resident red grouper) with the cameras directed at the hole. Two to five units were simultaneously deployed at different


8 locations arou nd a given site and recorded audio and video continuously for up to 24 hours (Table 1) Additional c ustom Digital SpectroGram (DSG) audio recorders were deployed to provide a longer time series for periodicity analyses: four on Steamboat Lumps with a du ty cycle of 2.5 minutes every 10 minutes for five days, and three recorders at Madison Swanson with a duty cycle of eight minutes every 10 minutes for two days (Table 1). These units consisted of a cylindrical PVC housing, a single HTI 96 MIN hydrophone ( sensitivity = 186 1 dB re: 1V/ 37 kHz ), micro computer, circuit board, and were powered by 6 D cell alkaline batteries. Single channel audio was recorded at a sample rate of 50 kHz, and was saved on Patriot 16 GB SanDisk secure digital flash memory cards (SanDisk Corporation, Milipitas, CA). Individual recording units were attached to anchored line using steel gangion snaps and c able ties placed approximately three meters above the anchor, with a single float 30 meters above the unit to prevent sinking, as well as surface buoys for re location and retrieval (Figure 2) Units were deployed from the deck of the ship in the general vicinity of active grouper holes Analysis of Sounds Audio portions of video recordings were used for descriptive analyses, as these units were placed in closest proximity to fish, and therefore contained the clearest and most consistent sounds. Audio tracks were separated from each MPEG video file using


9 Ulead VideoStudio 11.0 (Corel Corporation, Ottawa, Canada, and saved as 16 bit WAV files. MPEG files recorded during nighttime hours were often highly compressed, and were manually divided into two hour sections prior to analysis. F iles longer than 10 hours were split into two separate files using Servant Sala mander 2.51 (ALTAP, Novy Bor, Czech Republic, before they could be opened in Ulead. Each WAV file was initially analyzed using Raven Pro 1.3 (Cornell Laboratory of Ornithology, Ithaca, NY, www ) software. Spectra were generated with a Hann window and discrete Fourier trans form (DFT) size of 4096 samples, and frequencies from 0 1200 Hz were viewed in 30 second windows. Individual red grouper sounds were manually selecte d (selection boxes included approximately two seconds beyond the end of each call, to serve as a measure of background noise) and saved as separate 16 bit WAV files with a sample rate of 44.1 kHz T he Batch Channel Exporter was then used to create separat e WAV files for each channel. MATLAB 7.7 (The Mathworks, Inc., Natick, MA, ) was used to resample each call to 4410 Hz All video recorders were calibrated by presenting 0.1 V peak test sine waves at 10 20, 50, 100, 150, 200, 400, 700, 1 ,000 and 1 5 00 Hz and determining the frequency response For each recorder, the unique frequency response was used to create a custom finite duration impulse response (FIR) filter which was then applied to the r esampled WAV file s from that recorder Signal to noise ratios


10 (SNRs) were calculated for each corrected file, and all files with SNR > 2 were included in subsequent analyses. Start time and root mean square (RMS) amplitude were then generated for each fi le Files from the same site and time were categorized as replicates (i.e. the same call was recorded on more than one unit) and calls with the highest RMS amplitude for each replicate were included in final analysis. Additional manual analysis in Rav en was performed on each call: spectra (Hann window, DFT size: 1024 samples, 0 2205 Hz) were used to generate peak frequency measurements W aveform plots were used to measure durations and inter pulse intervals. Custom MATLAB programs w ere used to calcul ate all other measurements, including amplitudes, bandwidths and sound pressure levels. Behavioral Analysis Analysis of video footage associated with sounds was performed using Ulead. Video from all recorders was visually inspected for each sound event included in the descriptive analysis. Although only the best replicate was included in the sound analysis, all replicates were included in the behavioral analysis, as fish were not necessarily visible in footage from all units Observations were made fo r at least 10 s before and after each sound, and included the number of fish observed and a general description of behavior at the time of sound production. Sex of individuals was noted if possible, based on distinct display coloration patterns : m ales hav e darkening along the dorsum, and females exhibit


11 several broad white vertical bands along the body (C. Koenig, pers. comm.). B ehavioral observations were combined and summarized for each replicate. Periodicity Analysis Periodicity of sound production was measured by manually browsing spectrograms from DSG recordings using Raven ( Hann window, DFT = 4096 samples, 0 1000 Hz, 30 second increments). Each spectrogram was visually analyzed, and all red grouper sounds were logged, generating a total number of calls recorded for each file. Of 3,644 files recorded, 1,002 were excluded from analysis because backgrou nd noise was present at levels likely to mask detection of red grouper calls. Engine noise from the Liberty Star was the largest contributor to back ground noise, although abrasion of the PVC housings by the steel gangions also produced intermittent noise sufficient to cause masking. Call rates were calculated by dividing the total number of calls per recording by the duration (e.g. 12 calls/2.5 minut es = 4.8 calls/minute). End time was used to categorize each recording into 30 minute and 1 hour time of s 13:29; 08:00 08:59) C all rates and counts for each bin were then ave raged across all days to calculat e mean number of calls a nd call rate for t hat time of day. When comparing number of calls from both SL and MS, only calls recorded in the first 2.5 m inutes of MS files were included.


12 RESULTS Description of Sounds Red grouper were found to produce a unique series of low frequency pulses and two distinct variations were observed Short c alls were compo s ed of one to four brief pulses followed by a down swept buzz (Figure 3 ) Pulse train calls comprised a short call immediately followed by a rapid series of broadband b ursts (Fig ure 4 ) Applying the SNR > 2 threshold res ulted in 167 short calls, 100 of which were randomly selected for analysis, and 16 pulse trains, all of which were included in analysis. Descriptive statistics were calculated for each call type separa tely (Table 2) Inferential s tatistical comparisons between call types were not performed because there was no way to know how many individual fish may have been recorded. Fast Fourier t ransforms (FFTs) of all calls were averaged to generate a mea n FFT ( Figure 5 ), sh owing a dominant frequency around 180 Hz. T his 180 Hz frequency peak is also reflected in the distribution of peak frequency measurements (Figure 6 ). Energy below 50 Hz was likely due to vessel noise, and inclusion of this energy in peak fr equency measurements explains the lower mean peak frequencies (150 Hz for short calls, 131 Hz for pulse trains) reported in Table 2. Six dB bandwidth measurements (Figure 7 ) indicate most energy lie s between 50 31 0 Hz. R oot mean square (rms) r eceived sou nd pressure levels (SPLs)


13 ranged from 110 (Figure 8 ) W hile actual source lev els were not obtained, the proximity of recording units to fish suggest s that maximum received levels (e.g. 142 dB SNR dB = 37) may serve as a close appr oximation F or example, fish observed directly in front of a recorder, at an estimated range of <3 m, produc ed a pulse train sound at 127 rms Call duration increased with the number of pulses, and varied from 1 3 s for short calls and from 3 22 s for pulse trains (Figure 9 ). Behavior Video ana lysis was performed for all 116 calls included in the descri ptive analysis O f these calls 56 sounds occurred at night, while 35 sounds had no red grouper visible in video footage Red grouper behavi or observed during sound production fell into two cat egories: territorial activity and courtship interactions. Territorial activity included patrolling where a male swims in a repea ted pattern around and above a hole ( n = 12 ) and color change s ( e.g. dar kening of dorsum ; n = 3). C ourtship interactions consisted of a male and female observed swimming together (n = 10) R apid swimming with direct physical contact between a male and female occurred during four of these interactions although no apparent sp awning was observed A single male was observed for all sounds associated with territorial activity; one male and one female were present during courtship interactions. Short calls were associated with all behaviors, and pulse trains were associated with patrolling, color change and courtship with direct body contact. A summary of each sound behavior event is given in Table 3.


14 Diel Periodicity Red grouper were found to produce sounds at all times of day and night and showed a strong die l pattern of s ound production (Figure 10 ) Calling in creased just before dawn, dropped off briefly after sunrise, then increased throughout the day peaking in the late afternoon before dropping off again after sunset (Figure 11 ) While both MS and SL exhibited simila r patterns of sonic activity, SL had higher daytime calling rates, and MS had a later afternoon peak. Only short calls appeared to exhibit a daily pattern; calls with pulse trains were found at low levels throu gh both day and night (Figure 12 ). W ithout an accurate assessment of fish abundance statistical comparisons between sites can not be made T he increase in call rates could be attributed to greater numbers of fish rather than increased activity of individuals; it is interesting to note, however, t hat nighttime call rates we re similar at both locations.


15 DISCUSSION In situ s ounds produced by red grouper ar e similar to low frequency pulsed sounds reported for other free ranging epinephelids, including Nassau grouper and red hind (Moulton, 1958; Steinberg et al. 1962; Steinberg et al. 1965) as well as go liath grouper (Mann et al. 2009) The frequency range and pulse duration are consistent with agonistic sounds produced by captive red grouper described by Fish and Mowbray (1970) but the overall call structure was found to be more complex No direct observat ions of spawning were made. This could be explained by a) red grouper do not produce sound during the act of spawning; or b) spawning occurred during one of the 91 sounds produced either at night or while red grouper were not visible in video footage. Ad ditional video analysis is necessary to confirm whether sound production is directly related to spawning. Nevertheless, r ed grouper were found to produce sounds during a known peak spawning month (May) T his finding combined with observations of calls m ade during ter ritorial displays and courtship suggests that sonic activity may b e linked to reproductive behavior. This relationship is further supported by evidence that sounds are produced by males during patrolling and interaction with females which is similar to behavior of the closely related red hind (Mann and Locascio, 2008)


16 Crepuscular peaks in calling activity have been observed in several species that also typically spawn at dawn and/or dusk. M ann and Lobel (1995) found that damselfish ( Dascyllus albisella ) sound production peaked at dawn and corre sponded with spawning activity. Winn et al. (1964) found that longspine squirrelfish ( Holocentrus rufus ) sound production peaked at both dawn and dusk, and was re lated to terr itorial displays. Evening spawning has been observed in tiger grouper ( M. tigris ) (Sadovy et al. 1994) leopard grouper ( M. rosacea ) (Erisman et al. 2007) halfmoon grouper ( E. rivulatus ) (Mackie, 2007) and dusky grouper ( E. marginatus ) (Hereu et al. 2006) but i nformation on patterns of sound production for these species is not available However, if red grouper do spawn in the evening, observed increases in late afternoon calling activity would sugg est that sound production is linked to spawning. T he results of this study indicate that passive acoust ics could potentially be used to monitor red grouper reproductive activity. The significance of this work lies in the potential for using passive acou stics as a method for monitoring fish populations Locascio and Mann (2008) dem onstrated the utility of passive acoustic monitoring for studying reproductive activity in soniferous fishes, and its applicability over a broad range of spatial and temporal scales. P assive acoustics could be used in defining spawning grounds for those s pecies that produce sounds directly associated with spawning behavior (Mok and Gilmore, 1983; Luczkovich et al. 1999) Numerous studies suggest that fisheries closures particularly of spawning sites, may be an effective management strategy. Red hind in the U.S. Virgin Islands have bene fitted from seasonal closures of a spawning aggregation site, with size increases of


17 spawning adults and a favorable shift in female to male sex ratio (Beets and Friedlander, 1998; Nemeth, 2005) Additionally, Nemeth (2005) reported that establishing a permanent marine protected area surrounding the same aggregation site resulted in a 60% increase in stock density and biomass. Coleman et al. (2000) recommend ed establishing networks of large Marine Protected Areas (MPAs) for managing species including red grouper that may be highly susceptible to overfishing. Similarly, Koenig et al. (2000) emphasize d the importance of protecting habitat by establishing reserves, which would then allow researchers to better understand productio n in un fished areas. However, the widespread di stribution, protracted spawning season, and lack of seasonal movement of red grouper make designation of critical habitats and effecti ve fishery closures challenging S mall areal closures may not protect sufficient numbers of fish, while large and/or wide spread closures are difficult to enforce. Deployment of passive acoustic recorders throughout the known range of red grouper could provide a detailed map of their distribution. If sound production proves to be closely linked to spawning behavior habitat use could then be more clearly defined. This approach would enable identification of critical habitats and, ultimately, designation of reserves for red grouper. Red grouper, along with all marine o rganisms that rely on sound for communication may be i mpacted by increasing levels of anthropogenic sound in the ocean. Oil and gas exploration, vessel traffic, scientific research and military activity all contribute acoustic energy to the marine environment (Hildebrand, 2009) Low


18 frequency components attenuate least, and therefore travel farthest, so those species relying on low frequency sounds to communicate like red grouper are most likely to be affecte d. Shipping noise has risen to such levels that global deep water ambient noise has increased 10 to 100 fold for frequencies below 300 Hz over the last 50 years (Ross, 2005) At a minimum, this noise will likely cause an increase in signal masking below 300 Hz. Masking occurs when noise levels increase (relative to a signal of interest) to the point that a receiver is no longer able to discriminate between the signal and backg round noise M asking may interfere with social communication, predator avoidance, prey detection, and other import ant signals Vasconcelos et al. (2007) demonstrated that vessel noise negatively affected hearing and conspecific communication in the Lusitanian toadfish ( Halob atrachus didactylus ) Codarin et al. (2008) report th at masking occurred in the presence of ship noise for drum ( Sc i aena umbra ) and damselfish ( Chromis chromis ). R ecent research suggest s that ocean acidification due to increasin g atmospheric carbon dioxide is likely to result in decreased sound abs orption for frequencies below 10 kHz (Hester et al. 2008; Brewer and Hester, 2009) Ocean acidification could exacerbate the already increasing levels of ocean noise, and amplify the potential for masking of acoustic cues. Long term noise exposure effects have been examined in terrestrial animals, but ocean noise research has focused almost entirely on marine mammals (Wright et al. 2007; Clark et al. 2009) Very little is currently being invested in studying lower profile species such as fish U nderstanding the acoustic


19 communication of red grouper will lay the fou ndation to determine their susceptibility to noise pollution The results presented in this study offer new insight into the acoustic behavior of red grouper in their natural environment and provide a framework for future passive acoustic research B et ter understand ing of spatial and temporal patterns of red grouper reproductive activity will enable implementation of management practices aimed at optimizing spawning and recruitment, while at the same time maintaining a productive fishery As a keystone species, red grouper play an important role in maintaining biological diversity and abundance Given the value of red grouper, both in terms of human economics and ecosystem balance effective conservation and management strategies are crucial.


20 Table 1 Location, deployment and data collection inform ation for all recorders Depth (m) Deployment Date & Time (EST; 2008) Retrieval Date & Time (EST; 2008) Sample Rate (kHz) Unit Location Video Audio Duty cycle SL1 2812.3' N 8443.0' W 1 75.0 7 Ma y 13:39 8 May 09:00 Yes Stere o 44.1 Continuous SL2 2812.3' N 8443.0' W 1 75.0 7 May 13:39 8 May 09:00 Yes Stere o 44.1 Continuous SL3 2812.3' N 8443.0' W 1 75.0 7 May 13:39 8 May 09:00 Yes Stere o 44.1 Continuous SL4 2812.3' N 8443.0' W 1 75.0 7 May 13 :39 8 May 09:00 Yes Stere o 44.1 Continuous SLA 2812.3' N 8443.0' W 1 73.2 7 May 08:22 8 May 09:00 Yes Stere o 44.1 Continuous DSG1 2812.4' N 8443.0' W 1 75.0 7 May 17:52 13 May 07:44 No Mono 50 2.5 min/10 min DSG2 2812.3' N 8443.0' W 1 90.2 8 May 16:2 0 13 May 07:34 No Mono 50 2.5 min/10 min DSG3 2812.3' N 8443.0' W 1 71.9 8 May 15:56 13 May 07:54 No Mono 50 2.5 min/10 min DSG4 2812.3' N 8442.9' W 1 71.9 8 May 15:32 13 May 08:06 No Mono 50 2.5 min/10 min DSG5 2916.7' N 8538.8' W 2 57.9 9 May 12:49 11 May 12:41 No Mono 50 8 min/10 min DSG6 2916.8' N 8538.8' W 2 57.3 9 May 12:28 11 May 12:10 No Mono 50 8 min/10 min DSG8 2916.6' N 8538.7' W 2 59.4 9 May 13:05 11 May 12:52 No Mono 50 8 min/10 min MS1 2915.2' N 8541.3' W 2 65.8 10 May 13:24 11 May 07:35 Yes Stere o 44.1 Continuous MS2 2915.2' N 8541.3' W 2 64.0 10 May 09:26 11 May 07:35 Yes Stere o 44.1 Continuous MS3 2915.2' N 8541.3' W 2 64.0 10 May 09:26 11 May 07:35 Yes Stere o 44.1 Continuous MS4 2915.2' N 8541.3' W 2 65.8 10 May 13:24 11 M ay 07:35 Yes Stere o 44.1 Continuous MSA 2915.2' N 8541.3' W 2 64.0 10 May 09:26 11 May 07:35 Yes Stere o 44.1 Continuous SL5 2812.1' N 8443.0' W 1 70.4 12 May 12:51 13 May 09:05 Yes Stere o 44.1 Continuous SL6 2812.1' N 8443.0' W 1 70.4 12 May 12:51 13 May 09:05 Yes Stere o 44.1 Continuous SL7 2812.1' N 8443.0' W 1 70.4 12 May 12:51 13 May 09:05 Yes Stere o 44.1 Continuous SL8 2812.1' N 8443.0' W 1 70.4 12 May 12:51 13 May 09:05 Yes Stere o 44.1 Continuous 1 Steamboat Lumps Marine Reserve 2 Madison Sw anson Marine Reserve


21 Table 2 Descriptive statistics for red grouper calls. Call Type Measure Mean SD Min. Max. CV (%) 6 Short (n=100) Peak Frequency (Hz) 150 51 39 190 34 6 dB Bandwidth (Hz) 148 57 3 260 38 Call Duration (s) 1.9 0.3 1.4 2.8 14.9 # Pulses/Call 4 1 3 7 19 Mean IP 1 Pulse Duration (ms) 161 33 67 244 20 Mean IP 1 Inter pulse Interval 4 (ms) 355 51 272 440 14 CP 2 Pulse Duration (s) 0.7 0.2 0.5 1.2 21.0 CP 2 Peak Frequency (Hz) 112 56 35 237 50 Peak Amplitude (mV) 114 118 13 733 10 4 Received SPL 5 (dB re: 1 Pa rms ) 124 6 110 142 5 Pulsetrain (n=16) Peak Frequency (Hz) 131 63 13 185 49 6 dB Bandwidth (Hz) 118 62 30 179 53 Call Duration (s) 7.7 5.4 2.5 22.4 70.9 # Pulses/Call 33 16 11 57 50 Mean IP 1 Pulse Duration (m s) 153 43 92 224 28 Mean IP 1 Inter pulse Interval 4 (ms) 370 43 286 448 12 CP 2 Pulse Duration (s) 1.8 0.2 1.5 2.2 11.8 CP 2 Peak Frequency (Hz) 89 55 35 202 62 Mean PT 3 Pulse Duration (ms) 113 42 50 195 37 Mean PT 3 Inter pulse Interval 4 (ms) 201 76 105 391 38 Peak Amplitude (mV) 88 49 24 184 56 Received SPL 5 (dB re: 1 Pa rms ) 122 4 116 128 3 1 IP: introductory pulses 2 CP: central pulse 3 PT: pulse trai n 4 Inter pulse intervals were measured as the time from the first positive peak of one pulse to the first positive peak of the subsequent pulse. 5 SPL: root mean squ ar e (rms) sound pressure level, dB relative to a reference pressure of 1 Pa 6 CV = coefficient of variation calculated as 100*(SD/Mean)


22 Table 3 Sound properties and observed behaviors of red grouper Recorder Time (EST) Type 1 RL 2 (dB re: 1 Pa rms ) Peak F requency (Hz) # Pulses Dur (s) Sex Behavior 3 SL4 18:41 short 124 43.1 5 2.1 m patrol SL5 17:01 short 120 176.6 4 1.8 m patrol SL5 17:04 short 122 176.6 3 1.5 m patrol SL5 17:57 short 125 176.6 4 1.9 m patrol SL5 18:13 short 131 176.6 5 1.8 m patrol S L6 17:14 short 123 180.9 3 1.4 m patrol SL6 18:24 short 119 176.6 4 2 m patrol SL6 18:26 short 120 176.6 4 1.5 m patrol SL6 18:28 short 124 180.9 5 1.8 m patrol SL6 18:30 short 120 176.6 4 1.8 m patrol SL6 18:35 short 122 180.9 5 1.9 m patrol SL6 18: 48 pt 120 176.6 14 3 m patrol SL2 18:14 short 126 47.4 5 2.1 m color change SL5 18:18 short 125 180.9 5 1.8 m color change SL8 18:01 pt 116 159.3 15 3.8 m+f color change SL5 16:55 short 122 180.9 3 1.6 m+f courtship SL5 17:58 short 128 180.9 5 2.3 m+f courtship SL6 16:46 short 126 176.6 4 1.6 m+f courtship SL6 16:48 short 119 137.8 3 1.6 m+f courtship SL6 16:51 short 120 180.9 3 1.6 m+f courtship SL6 16:52 short 120 180.9 4 1.6 m+f courtship SL1 18:30 short 124 38.8 5 2.3 m+f courtship w/ dbc SL5 17:49 short 125 176.6 4 1.8 m+f courtship w/ dbc SL6 16:20 pt 127 180.9 16 3.4 m+f courtship w/ dbc SL6 16:49 pt 119 176.6 28 3.6 m+f courtship w/ dbc 1 pt: pulse train 2 RL : received sound pressure level, dB relative to a reference pressure of 1 Pa 3 dbc : direct body contact


























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ABOUT THE AUTHOR Misty D. Montie was born in Missoula, MT, and earned a B.A. degree in Environmental Biology from the University of Montana in 2000. She has received two Honorable Mentions from the National Science Foundation Graduate Res earch Fellowship Program, and is the recipient of a National Defense Science and Engineering Graduate Fellowship.