Listening to Fish Passiveacoustic Applications in Marine Fisheries

Listening to Fish PassiveAcoustic Applications in Marine Fisheries

8- /0 Apri!2002 An /nternational 8'orkshop on the Applications of Passive Acoustics in Fisheries Massachusetts/nstItute of Technology SeaGrant College Program Cambnc/ge,MA Listening to Fish Passive Acoustic Applications in INarine Fisheries

Edited by Rodney Rountree',Cliff Goudey',and Tony Hawkins'

' School for Marine Scienceand Technology,UMASS Dartmouth,706 South Rodney FrenchBlvd., New Bedford, MA 02744

' Center for FisheriesEngineering Research,MIT SeaGrant College Program,Bldg, NE20-376, 3 CambridgeCenter, Cambridge, MA 02139

' Environment 5 Society at the University of Aberdeen,St Mary's, KingsCollege, Aberdeen, AB24 3UF, UK

Acknowledgements

Specialthanks to Margaret Weigel of MITSeaGrant College Programfor layout duties, and GraceLee and Margaret Weigel for web layout work,

These proceedings are from the International Workshop on the Applications of Passive Acoustics to Fisheries,April 8-10,2002, sponsored by MIT SeaGrant College Program,Office of Naval Research ONRCode 342,Marine Mammal 58' Program!,and National UnderseaResearch Program, with additional support from SMAST,UMass-Dartmouth, Connecticut Sea Grant, Florida Sea Grant, Hawaii Sea Grant, Louisiana Sea Grant, North Carolina Sea Grant, South Carolina Sea Grant Consortium, Texas Sea Grant and Woods Hole Sea Grant.

MITSG 03-2

Proceedings from the international Workshop on the Applications of Passive Acoustics to Fisheries 1 Proceedingsfrom the Internationa! Workshopon the Applications of PassiveAcoostics to Fisheries 2 TABLE OF CONTENTS

Listening to Fish: Proceedingsof the International Workshopon the Applications of Passive Acoustics to Fisheries Rodney Rountree,Cliff Goudey,and Tony Hawkins.

Section 1

Passive Listening for Fishes;What Has Been Done? ..15

Locating sciaenid spawning aggregations in anticipation of harbor modifications, and reactions of spotted sea trout spawnersto acoustic disturbance

Mark Collins,Bridget Callahan,Bill Post,and ArnandaAvildsen ,. 17

Characterizationof sounds and their use in two sciaenidspecies: weakfish and Atlantic croaker Martin A.Connaughton, Michael L. Lunn, Michael L Fine,and Malcolm H. Tayor,...... 21

Detectionand characterization of yellowfin and bluefin tuna using passive acoustical techniques Scott Allen and David A. Derner...,...,...... ,,..., ...,...,.... 26

AcousticCompetition in the GulfToadfish apsonus beta: Crepuscular Changes & AcousticTagging MichaelL. Fine and RobertF, Thorson 29

PassiveAcoustic Field Researchon Atlantic Cod,Gadus morhua L, in Canada

SusanB. Fudge and George A. Rose 34

PassiveAcoustic Transects; Mating Calls and Spawning Ecology in EastFlorida Sciaenids R,Grant Gilmore, Jr. ..39

The Useof PassiveAcoustics to Identifya HaddockSpawning Area Anthony D. Hawkins...... 49

Using a TowedArray to Survey Red Drum Spawning Sitesin the Gulf of Mexico Scott A. Holt . .. 54

Fish Courtship and Mating Sounds

Phillip S. Lobel ..60

UsingPassive Acoustics to Monitor Spawningof Fishesin the DrumFamily Sciaenidae! Joseph J. Luczkovichand Mark W. Sprague ,. 65 Are acoustic calls a prernating reproductive barrier between two northeast Atlantic cod Gadus morhua! groups a review Jarle Tryti Nordeide and Jens Loss Finstad,...,,,...... ,...,...... 70

Applicationsof underwateracoustics data in fisheriesmanagement for spotted seatrout, Cynoscionnebu/osus, in estuaries of South Carolina

Bill Rournillat and Myra Brouwer, ,,76

Soniferous Fishes of Massachusetts

RodneyRountree, Francis Juanes, and Joseph E.Blue. ..83

The mating behaviour of Atlantic cod Gadusmorhua!, SherrylynnRowe and Jeffrey A. Hutchings . ..91

Section 2

Technology,Future Developments and Applications. .. 97

Spotted Seatrout Spawning Requirementsand EssentialFish Habitat:A Microhabitat Approach Using Hydrophones

Donald M. Baltz 99

Creating a Web-basedLibrary of Underwater Biological Sounds JackW. Bradbury and Carol A. Bloomgarden. .. 103

Potentialfor couplingof underwaterTV monitoringwith passiveacoustics CharlesA. Barans,David Schmidt,and Myra C. Brouwer .. 107

Applicationof PassiveAcoustic Methods for Detection,Location and Tracking of Whales Christopher W. Clark . 112

Multihydrophone localization of low frequency broadband sources Stephen E.Forsythe ,. 117

PassiveDetection and Localizationof TransientSignals from MarineMammals using Widely Spaced Bottom Mounted Hydrophones in Open Ocean Environments Susan Jarvis and David Moretti 123

Synchronizedunderwater audio-video recording

Phillip S. Lobel . .. 136 New technologies for passiveacoustic detection of fish sound production David A. Mann. . 140

Potentialfor the useof RemotelyOperated Vehicles ROVs! as a platformfor passiveacoustics. RodneyRountree, Francis Juanes, and Joseph E.Blue ...,..., .. , 144

Quantifying Species-SpecificContributions to the Overall Sound Level Mark W.Sprague and Joseph J, Luczkovich. .. 153

A remote-controlledinstrument platform for fish behaviourstudies and soundmonitoring Ingvald Svellingen,Bjern Totland,and JanTore Svredal . .. 160

ClassifyingFish Sounds Using Wavelets Mark Wood .. 163

Section 3

Working Group Summaries ., 169

A summaryreport on the Biology Sessionand Biology Working Group from the International Workshopon the Application of PassiveAcoustics in Fisheries, Joseph J. Luczkovich 171

Working Group on Technology Issues David Mann . ., 180 Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 6 ~ Listening~ ~ ~to Fish: ~ ~ Proceedings ~ ~of the ~International ~ ~ Workshop on the Applications of Passive Acoustics to Fisheries

RodneyRountree', Cliff Goudey',and Tony Hawkins'

'Schoolfor MarineScience and Technology, UMASS Dartmouth, 706 South Rodney French Blvd, New Bedford, MA 02744

'Centerfor FisheriesEngineering Research, MIT Sea Grant College Program, MIT Bldg. NE20-376, 3 CambridgeCenter, Cambridge, MA 02139

' Kincraig, Blairs,Aberdeen, Scotland AB12 SYT

Workshop06jecthtes 1. Convenean international conferenceto assessthe potential of passiveacoustics as a tool with applicationsin fisheriesand marineconservation in estuarine,coastal and oceanicecosystems. 2, Topromote the useof passiveacoustics for exploringthe oceans,surveying marine biodiversity, and assessingthe impact of man's activities upon the oceans. 3. Developan internationalresearch initiative to exploreand extend the useof passiveacoustics in the marinesciences in both appliedand non-appliedfields, and to developpotential researchtheme areasfor future funding.

introduction OnApril 8-10,2002,MIT Sea Grant hosted an internationalworkshop on the applicationof passive acousticsin Fisheriesin Dedham,Massachusetts, The'hands-on'workshop drew over 40 European and NorthAmerican experts from fisheries,fish biology,acoustics, signal processing, underwater technologyand other relatedfields. The workshop was divided into 4 sessionsand 2 working groupswith a totalof 29 presentationsdelivered. The first sessionentitled:"Passive Listening for fishes- what has been done?" reviewed past and current researchactivities, while the second session "Future developments and applications" examined recommendations for future research and exampleswhere existing programs could be enhancedby passiveacoustic technology. The third session"Acoustic technology" reviewed the stateof the art and future developmentsfor underwater acoustic and related technologies, A special sessionincluded demonstrations of hardwareand software,The workshop was caped off by a workinggroup on the biologicaland ecologicalaspects of passiveacoustic research, moderated by Joe Luczkovichof EastCarolina University, and a working groupon technologyand softwareissues moderated by DavidMann of the Universityof Southern

Proceedingsfrom the internationai Workshop on the Applications of PassiveAcoustics to Fisheries 7 Florida in St. Petersburg. A web page was constructed to document the findings of the workshop http:Ii'web.mit.edu/seagrant/acoustics/index.html!.

The workshop was a greatsuccess at bringing together an outstanding group of international researchersto exchangeresearch results, knowledge and ideasrelated to the applicationof passive acousticsto fisheries,census of marinelife and relatedissues. The workshop demonstrated the high potential of passiveacoustics as a researchtool for fisheries and related fields through the presenta- tion of the results of a number of successfulresearch projects. One of the important outcomes of the workshop was the exchangeof information about ongoing and past researchprojects that have successfullyused passive acoustics. Previously, many of thesescientists had beenworking in isolation with little interaction with their colleaguesworking acrossNorth America and overseas.The fisheriesbiologists participating in the workshopalso gained valuable insight from exchangeof information with scientistswith well-establishedbackgrounds in the use of passiveacoustics to study marine cetaceans seeClark, Jarvis and Moretti, herein!. Another important result was the exchange of hardwareand software technologies among the participants. The workshop has already fostered renewedenthusiasm among the participants for this field of researchand has resulted in new domesticand international collaborations. In addition, the workshop brought researcherstogether with administrators,staff and scientistsfrom severalfunding agenciesand with the media e.g.,NURP, National Geographic,etc.!. Finally,extensive discussionof the future research priorities for passiveacoustics, and development of both domestic and international collaborations, areexpected to go a longway towards promoting the applicationof passiveacoustic technology to fisheriesand relatedfields. Some of the mostimportant researchinitiatives identified by the workshop participants were: 1! the importance of developing a national databaseof historic underwater sound archives see Bradburyand Bloomgarden,herein!,2! the importance of establishing a National/International ReferenceLibrary of fish sounds, which would be guided by an international panelof scientistsdrawn in part from the workshopparticipants,3! the importanceof establishing an international researchand training center for passiveacoustics applications to fisheries and marine census potentially at Grant Gilrnore'sLaboratory at the Kennedy SpaceCenter!, and 4! the importance of active promotion of the technology through publications of the workshop proceedings and related articles, Many more specific researchneeds in biology and technology were addressedand are presentedthroughout these proceedings,

Background Fishare difficult to seeand study in the ocean. SCUBAtechniques can help in shallow waters and a rangeof activeacoustic and optical techniques can assist in deepwater, but we are still largelyigno- rant of the distributionand behavior of the great majorityof marinefish. Possiblyone of the greatestchallenges to researchersattempting to studythe behavioralecology of fishesis that of finding the fish in the first place.Often a scientistmust go to great lengths conducting expensive and time consuming biological surveyssimply to determine the locations or habitats where a fish can be found,before any attempt to studyits biotic and abiotic interactionscan be made.After all,you can't study something you can't find. Any tool that can help scientists to locate fish is therefore

Proceedingsfiorn the international Workshopon the Applications of PassiveAcoustics to Fisheries 8 valuable. Fishtoo face the problem of assessingtheir environment, navigating through it, and com- municating with others of their kind. A surprisinglylarge number use sound to overcome the prob- fern of living in a visuallyopaque medium.

Over800 species of fishesfrom 109families worldwide are knownto be vocal,though this is likely to be a great underestimate. Of these,over 150 speciesare found in the northwest Atlantic Fish and Mowbray1970'!, Amongst the vocalfishes are some of the mostabundant and important commercial fish species,including cod, haddock and the drum fishes sciaenidae!.

Passiveacoustics offers a unique tool to study these fishes,which often live in dark and turbid watersand are difficultto observeby other means.Passive acoustic techniques can be usedto locateconcentrations of particularspecies, especially during their vulnerablespawning stage. This in turn allows spawning habitat to be identified, mapped, and protected. It can allow the numbers of fishto be assessed,And it canbe usedto gaina betterunderstanding of fish behaviour,including fish migrations. Passiveacoustics can also be used to simuitaneously monitor sourcesof noise pollution,and to studythe impactof man'sactivities on marinecommunities, Anthropogenic sourcesinclude noise generated by boating activity, seismic surveys,sonars, fish-finders, depth finders,drilling for oil andgas, and militaryactivities. These all havean unknownbut potentialirnpor- tant impact on marinefauna. We believe that passiveacoustic technologies hold special promise andwill becomeimportant tools in the comingyears. However, it hasbeen largely ignored in the northwestAtlantic in the studyof fishesimportant in the marinefood chain. It is alsoa technique that is amenableto cooperativeresearch with commercialfishermen, who canbring their own knowledge to such studies.

Applications to Fisheries Soundstravel much farther in waterthan light and underwatersounds, including fish calls,can often be heardover much greater distances than fish can be seen.Listening to fish cancontribute a great deal to our knowledge of their abundance,distribution and behavior. Passiveacoustics studiesusing relatively simple techniques have been successful in locatingconcentrations of important fish species,opening the way for further, more detailed studies of their behavior,distribution and habitatuse. As reflectedin the variousresearch programs described within this proceedings, alreadysignificant strides have been taken in the application of passiveacoustics to fisheries;

in an Arcticfjord in northernNorway, workers from the FRSMarine Laboratory, Aberdeen and the Universityof Tromsiahave located a spawningground of haddock,Melanogrammus aeglefinus. Passivelistening has revealed that this species,previously thought to spawnoffshore in deep water, can also form large spawning concentrations close to shore see Hawkins!.

Norwegian researchersare using passiveacoustics to study spawning behavior of Atlantic cod and other gadids see Nordeide and Finstad,Svellingen et al.!.

a number of studies in the estuariesof the eastern United States have helped to localize the spawning areasof drum fishesand demonstratingthe usefulnessof passiveacoustics as a tool for identificationof essentialfish habitatrequirements, as well asa toolto providefisheries

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 9 managerswith informationof sciaenidreproductive biology seeCollins et al.,Gilmore, Holt, iuczkovich and Sprague,Roumillat and Brower!. for the first time in the UnitedStates passive acoustics are beingexplored as a toolto census marinefishes on the continentalshelf, In one study, a towedhydrophone array is beingused to identifyspawning sites of reddrum in thewestern Gulf of Mexico see Holt!. In another study, passiveacoustics are beingused to cataloguesoniferous fishes in the StellwagenBank National MarineSanctuary see Rountree et al.,Rountree and Juanes!. One goal of thestudy is to determinethe feasibilityof usingpassive acoustics as a supplementaltool in the censusof fish diversity and habitatuse patterns in the sanctuary. anongoing survey of soniferousfishes of Massachusettshas resulted in a significantrange extensionfor the crypticestuarine and inshore fish, the striped cusk-eel, Ophidion marginaturn seeRountree and Juanes!. Extensive sampling over many decades with conventional gears in theregion had failed to recognizethe importance of stripedcusk-eel to thefauna, while passiveacoustics revealed it to be widespreadand abundant.This study demonstrates that evena low-budget,low-tech, approach to passiveacoustics can contribute significantly to the census of marine life.

New Technology Studiesdescribed at the workshophave pushed technology to new levelsthat will allow researchers to expandthe frontiersof fisheriesscience and ocean exploration: thepotential for combininghydrophone arrays with other underwater census technologies is beingexplored, including ROVs see Rountree et ai.,Luczkovich and Sprague!, underwater video seeSvellingen et alLobe!,Barans et al.!and active acoustics Fudge and Rose!. Lobel has pio- neeredthe use of advanced SCUBAtechnologies for studies of fish vocal behavior. researchersare beginning to looktowards existing acoustic arrays maintained by the Navyand other agenciesfor applications to fishes see Jarvisand Moretti!. Advancesare being made in thedevelopment of modelingtools and software for tracking vocal fish seeForsythe! and identifying individual fish seeWood!. Newtechnologies for detectingand recording underwater sounds are rapidly evolving see Mann!.

Historic archivesof fish soundsare being assembledand rescued from deterioration and will be madeavailable to researchersand the publicthrough the internet seeBradbury and Bloomgarden!.The establishment of internet access to librariesof fishsounds is an important step to more widespread use of passiveacoustics in fisheries scienceand related fields.

The Future of Passive Acoustics Althoughstudies described during the workshop reflect the rapidgrowth of researchon passive acousticsapplications to fisheriesand marinecensus, there are many areas where technicaldevel- opments are needed to promote future research:

Proceedingsfrom the internationalWorkshop on theApplications of PassiveAcoustics to Fisheries 10 Software

the development of sound recognition systems,based on wavelet analysisand other new techniques to enabie the automatic discrimination of different species. For a north Atlantic species, the haddock,it hasalready proved possible to distinguishthe voicesof individualmale fish see Wood!. automaticevent detection/analysis software to quantifytemporal patterns of soundsover long time periods.

localization/trackingsoftware see Forsythe!,

software allowing simultaneous analysisof video and audio data in behavior studies i.e.,click on the sound wave of a fish call ancfview the corresponding video frame in a secondwindow!. Thiscapability would allow rapidcorrelations of individualsounds and soundcomponents with behavior and functional morphology.

Theimprovement of passivelistening technology for systematicaliydetecting and recordingsounds at sea,including:

ship basedlistening systems, with danglingand towed hydrophones. bottom mountediistening systems based on underwatervehicles and pop-upbuoys. drifting sonobuoysystems, either storing the data,or telemeteringdata to shipsor shore-based listening stations, largehydrophone arrays, capable of localizingsound sources.

measurementof sourceievels, and calibration techniques for measuring the distance of sound sources.

Back-yardscience; Perhaps of equalimportance to passiveacoustics systems for usein the open oceanis the developmentof technologyto aid in smallscale, low budgetstudies of marinefishes in estuarineand inshorehabitats. We feel that passiveacoustics have a greatpotential as a toolto provide basicinformation on essentialfish habitatuse patterns, as it becomesmore widely used in classroomsand State and Federal sampling programs. Several studies presented at the workshop demonstratethe usefulnessof this type of researchto fisheries.A goodexample of this isthe dis- covery,using passiveacoustics, that striped cusk-eelsare abundant in Massachusettsestuaries, wheredespite a longhistory of conventionalsampling in the region,the specieswas thought to be a very rare straggler.Technologies to aid this type of researchinclude; archivalacoustic recorders - unmanned recorders for useon shipsof opportunityin manytypes of habitats. homingdevices to locatesound sources see Forsythe, Rountree et al.!. devicesthat allow simultaneous recording of both audio and video data.

hand-held devicesfor shore based,or small boat surveysin shallow water.

miniature ROVdesigned for both video and audio recording of fish behavior from small boats and from shore.

Proceedingsfrom the international Workshopon the Appiications of PassiveAcoustics to Fisheries ]1 Application of passiveacoustics in a wider range of habitats where Fishmay aggregate to spawn, For example:

mangrove areas,which are especiallydifficult to survey by conventional means,but where the diversity of Fishesmay be especiallyhigh.

coral reefs and rocky reefs,where again many speciesaggregate.

oceanic and inshore banks,where the massspawning of sound producing species,like cod and haddock, takes place. the deep sea,where many species like the moridsand macrouridsare suspected to be vocal from anatomical evidence,

estuaries - the primary spawning grounds for many economically important Fishes.

Developmentof local,regional, national and internationalnetworks of"listening posts" especially in estuarine and inshore waters. Incorporation of listening posts into local and regional environmental data networks like GoMOOSand the NOAA/OCRM/NERR'sSystem Wide Monitoring Program.

The Benefits of Passive Acoustics

non-invasive, non-destructive census of marine life, worksat night without bias versusvideo andother techniques that requirelights!. can provide continuous monitoring of Fishes.

provides remote census capabilities.

determine the daily and seasonalactivity patterns of Fishesincluding determination of discrete daily spawning times. a betterfoundation for the managementof exploitedspecies by mappingtheir distribution and pinpointing their spawning grounds. a betterunderstanding of the habitatpreferences of keyFish species e.g., Essential Fish Habitat "EFH"assessment in the US!,giving a better focus for their conservation. establishmentof baselinesfor the abundanceand distribution of keyfish species,allowing examination of the effects of future environmental change.

obtaining a wider knowledge of the behavior of those Fishthat cannot readily be studied by any other method.

can be used to monitor environmental noise and determine their sources. can be usedto examinethe impactof anthropogenicnoise on Fish,especially on spawning behaviors. networksof listeningposts can provide synoptic data on the occurrenceof Fishesand spawning activities on local,regional, national and global scales.

Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 12 Conclusion

Researchpresented at this workshop underscoresthe great strides that have been made in the application of passive acoustics to fisheries and related issues in the last two decades. It is clear from this body of work, that although passiveacoustics is currently largely overlooked as a research tool, it is a rapidly "up-and-coming"field of researchthat holds great promise for the future. It is our hopethat publicationof this proceedingwill stimulatethe growthof this field,and will encourage funding agenciesto support passiveacoustics research.

Acknowiedgements Thisworkshop and the publicationof the proceedingsbenefited by contributionsfrom manyindi- viduals.Grace Lee set up the web pageand did muchof the text and graphicslayout for the proceedings,The staff of the EndicottHouse and BrooksCenter provided outstanding conference facilitiesand supportfor the workshop.The workshop and publicationof the workshopproceedings received major funding from MIT SeaGrant, the Office of NavalResearch, and from the Northeast- GreatLakes Center of the NationalUndersea Research Program. Travel for someworkshop participants was funded in-whole, or in-part by; Connecticut SeaGrant, Florida SeaGrant, Hawaii Sea Grant,Louisiana Sea Grant, North CarolinaSea Grant, the South CarolinaSea Grant Consortium, TexasSea Grant, and the Woods Hole SeaGrant Programs.

Literature Cited 'Fish,M P.,and W H.Mowbray.1970. Sounds of WesternNorth Atlantic fishes. Johns Hopkins Press, Baltimore, MD,205 p.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 13 Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 14 Section 1

Passive Listening for Fishes: What Has Been Done' ?

Proceedingsfrom the internationalWorAshop on the Applications of PassiveAcoustics to Fisheries 15 Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 16 Locatingsciaenid spawning aggregations in anticipationof harbor modifications,and reactionsof spotted sea trout spawnersto acousticdisturbance

Mark Collins,Bridget Callahan,Bill Post,and Amanda Avildsen

SCMarine ResourcesResearch institute, SCDNR,Charleston, SC, USA

Introduction Theestuarine-dependent sciaenids are by far the most recreationaliy = economically!important fishesin theSavannah River SC/GA, USA! estuary. Regional populations of theprimary species have declinedin abundancein recentyears amid concerns about reducedspawning stock biomass. Most southernstates have responded by tighteningharvest regulations.

Plansfor majormodifications and deepening of the SavannahHarbor and shipping channel have generatedspecial concerns about exacerbatingsciaenid spawning stock reductions due to: 1! direct dredgingmortality; 2! acousticdisruption of spawningaggregations; or,3! reducing the acceptabili- ty to thefish of anypresently utilized spawning sites through alterations to thebathymetry, flow characteristics, etc.

Theestuaries of SC,GA,and northernFL differ in a numberof ways e.g.,higher tidal amplitudes,no seagrasses!from those to the north and south, and there are reasonsto believethat sciaenid spawningbehavior may alsodiffer. Studiesof sciaenidspawning in this centralregion have been limitedin number,producing for exampleonly three red drum spawninglocations: two in SCand onein GA.No studies have been conducted in the SavannahRiver. Thus, a passiveacoustic survey wasinitiated to definethe geographicand temporal distribution of spawningaggregations of the recreationallyimportant sciaenid species, determine site fidelity betweenyears, characterize spawning habitats,and determineeffects of dredgingactivity on aggregations.

Methods An acousticsurvey was conducted during August- November 2000 and February-November 2001 in the SavannahRiver estuary, with somecoverage of the shippingchannel offshore. A directional hydrophone,analog receiver, and audio recorder were used to detectand record signals, and specific locationsof spawningsites were determined through triangulation. Signal strength cluantified on a 1-5scale!, prominent bathymetric/structural characteristics, light phase, tide stage, current velocity,depth, temperature, salinity, and dissolved oxygen were recorded for eachlocation. Field activitieswere conducted on average3 days/week.Emphasis was on the lowerestuary where salini-

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 17 tieswere >15 ppt, but occasionalbroader surveys were conducted to ensurethat no spawning activity was occurring farther upriver.

DuringJune 2001, preliminary dredging operations began in one turning basinin the lowerharbor, whichhad been identified as the locationof oneof the primaryspawning aggregations of spotted seatrout.The reaction of thespawning aggregation to dredgingactivity was monitored through the end of the spawning season.

Results Recreationally/economicallyimportant sciaenidsencountered included red drum Sciaenops ocellatus,spotted sea trout Cynoscionnebulosus, black drum Pogoniascromis, and weakfishCynoscion regalis.Sporadic drumming of all speciesoccurred in variouslocations of the lowerestuary, However,six primary spawning sites were identified for spotted seatrout, one for weakfish,and one for black drum. All sites were in salinities > 16 ppt, and all were within 12.2river km of the river mouth.

Timeof dayof spawningvaried somewhat among species, but in generalit appearedto be anchoredaround sunset with peakactivity from about 1 hrbefore through about 3 hrafter. This wasespecially evident with spotted seatrout, which had the longestspawning season. As day lengthshortened and sunset occurred progressively earlier at the endof thesummer, spawning activity began earlier.

Spottedseatrout spawning activity took placeduring May-September, peaking in July-August. Watertemperature apparently was a seasonalspawning cue, as activity ceased abruptly and did not resumewhen there was a 2C dropto 24 C overa 2-dayperiod althoughspawning in lowertem- peratureshas been previously reported!. All sixsites located in 2000were again used in 2001,but activity did not begin at all sites simultaneously.The sites had severalcharacteristics in common: theywere in themain river channel rather than side-creeks, they were in or adjacentto deepwater -10 m!,and they were associated with structureof sometype. Structure varied among sites, but wasgenerally a largechannel marker or a rockyarea such as a submergedjetty, Drumming activity appearedstrongest when a highor earlyebb tide occurred during the appropriate time of day.

Blackdrum spawned during late March to mid-Juneat riverkm 0 theriver mouth! in waterternper- aturesof 14-19'C.Weakfish spawning activity was concentrated just upriverat riverkm 2 during Juneto earlyOctober at temperaturesof 23,9-29.0'C.Weakfish appeared to be lesssite-specific thanblack drum or spottedseatrout, with the aggregation sometimes moving temporarily upriver andthen returning.Weakfish also tended to aggregatearound structure like spotted seatrout, althoughmore weakly, while blackdrum aggregatedin the middle of the channelwhere no structure could be detected.

Nolarge red drum spawning aggregations were located. A numberof times,individuals or very

Proceedingsfrom the internationai Workshop on the Applications of PassiveAcoustics to Fisheries 18 small groups of drumming males were found. This was most consistently at the mouth of the river and in the shippingchannel outside the mouth. All activitynoted wasduring August-September.

Theactive dredge in the vicinityof a largespotted seatrout aggregation began operations at the upriverend of the turning basin,the oppositeend from the aggregation,and movedslowly down- river.No changesin drummingintensity or periodicityrelative to the dredgewere noted. However, the spawningseason ended asconfirmed by checkingother known spawningsites! before the dredgeactually reached the fish;it was-100 rn awayat that point. Largeand smallvessels transited the areabut did not disturbthe fish. Oneacoustic disturbance that wasdramatically apparent, however,was a total cessationof drumming when bottlenose dolphin Tursiopstruncatus which make a pronounced acoustic signal! passedby, This behavior was also noticed on two occasionswith red drum.

Discussion

Passiveacoustic mapping of sciaenid spawning sites in preparation for harbor modifications was successful,lt confirmedspawning of important sciaenidspecies within the harborarea, and it definedthe spawningtemporally and spatially,There was considerable temporal overlap in spawning activityamong species, and in the lower 2 riverkm thereappeared to be spatialoverlap. However,on a finerscale hundredsof meters!there was little or no overlap.It is obvious,however, that the lower2 riverkm canbe consideredthe mostimportant sciaenid spawning area in the Savannahestuary, as all Fourspecies aggregated in that stretchof river, Aggregationsof reddrum were very small. Comparing this behavior to previous reports from the region is problematic due to the limitednumber of systemsthat havebeen studied; the aggregationin CharlestonHarbor, SC wasquite large,while the aggregationdetected in St.Helena Sound, SC was very small,Thus, it is not knownwhether red drum typicallyform largeaggregations in this region,or if in somesystems they generallyspawn in small groups.

Despitethe apparentimportance of acousticsignals in spawningaggregations for thesespecies, noisefrom boats,dredges, etc. does not interferewith drummingbehavior, even when the sourceof the noiseis close by, Certainly,these fish must be acclimatedto vesselpassage due to the factthat the SavannahRiver is a majorport. It is unknownwhether fish in a lesspopulous habitat would be so imperviousto anthropogenicnoise. The only responseto an acousticsignal was exhibited towardbottlenose dolphin, which prey on thesefishes; the cessationof drurnrningwas apparently a predator avoida nce behavior.

Whilespotted seatrout males do notrespond to dredgingnoise, it is unknownwhat effect a dredge would haveas it workedin the midstof the aggregation.Relatively large fishes e.g.,Atlantic stur- geonAcipenser oxyrinchus! are reportedwith someregularity having been sucked up by dredges elsewhere,Further, because two and possiblythree! of thesespecies appear to cue in on structures,removal of thesestructures, as commonly occurs during deepeningand channelizationopera- tions,may have a negativeimpact. Future research plans include statistical analyses of environmental variablesas related to drummingactivity, and re-examination in 2002 of spottedseatrout spawning behaviorin the turning basinthat wasdredged in 2001.

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries '19 Acknowledgments Haynevon Kofnitzassisted extensively in both field and laboratory.Bruce Stender verified identifi- cationsof larvalfishes, Joseph Luczkovich East Carolina University!, Mark Spraque East Carolina University!,Archibald McCallum University of Charleston!,Grant Gilmore DynarnacCorp.>, and Bill Rournillat provided invaluableassistance in verifying speciesidentifications from acoustic recordingsof aggregations,South Carolina Department of NaturalResources, Georgia Ports Authority, and Southern Liquid NaturalGas provided funding.

Proceedingsfrom the international Vyorkshopon the Appiications of PassiveAcoustics to Fisheries 20 Characterization~ ~ ~ of soundsand their use in two sciaenidspecies: weakfish and Atlantic croaker

MartinA. Connaughton', Michael L. Lunn', Michael L. Fine', and MalcolmH. Tayor'

'WashingtonCollege, 300 Washington Ave., Chestertown, MD 21620mconnaughton2@washcolkedu, milunn@ya hoo.corn

'Departmentof Biology,Virginia Commonwealth University, Richmond, VA 23284-2012,USA, [email protected],

'Collegeof MarineStudies and Department of BiologicalSciences, University of Delaware,Newark, DE 19716,USA, rntaylorOudel.edu.

Introduction Bothweakfish Cynoscion regalis and Atlantic croaker Micropogonias undulatus are members of the familySciaenidae, a groupof fishthat havebeen known to producesound since the turn of the 20thcentury, This family of fishesproduces sound through the useof highly specialized,extrinsic sonicmuscles which lie in closeproximity, but arenot attachedto, the swimbladder Tower 1908, Tavolga1964!. In weakfishand most sciaenids, sonic muscles are found only in the male;however, in others,including Atlantic croaker, the musclesare found in both malesand females Tower1908, Fishand Mowbray 1970!, Sound production has been linked to reproductive behavior in a number of sciaenidspecies Fish and Cummings 1972, Guest and lasswell1978, Mok and Gilmore1983, Saucierand Baltz 1993! and with fright or warningbehaviors in a fewspecies, including Atlantic croaker Fish and Mowbray1970!. The purpose of this paperis to characterizethe soundsproduced bytwo speciesof sciaenidand to discussthe rolesof thesesounds in the behaviorsof thesespecies.

Methods and Results

Weakfish experiments Fieldrecordings: Field recordings using a hydrophone Edmund Scientific! were made near the mouthof the DelawareBay at threestations along an inshore-offshore transect ranging from 1.24 to 5.64km from shore and varying in depthfrom 3.5 to 7.8m. One-minuterecordings were made at hourlyintervals over a 24hr periodon eight dates from mid-April through mid-August, encornpass- ing the late spring-earlysummer spawning season. Recordings of drummingsounds were ranked qualitativelyfrom 0- 4,with 0 representingno callsand 4 representingcontinuous calling by a chorus of individuals Connaughtonand Taylor 1995!.

Proceedingsfrom the International I@or%shopon the AppIications of PassiveAcoustics to Fisheries 21 Drummingwas highly seasonal, increasing dramatically from zeroin mid-Aprilto nearlymaximal levelsin earlyMay. Activity remained at nearrnaxirnal levels throughout Mayand June, and decreasedgradually in intensitythrough July and into August.Physiological indicators of reproductive readiness,including plasma androgen levels, male GSI, and the presenceof hydratedeggs were all high during the period of rnaxirnaldrumming activity. Drumming activity also expresseddiel trends, reaching maximal levels between 20:00and 24:00 hr sunset was between 19:50- 20:40! and declining to a minimum between 05;30and 10:30hr. Drumming activity, whether seasonalor diel, was most intense inshore,declining in intensity as one moved offshore Connaughton and Taylor, 1995!,The seasonality, evening timing, and inshorelocation of sound productionall coincidewith the knownreproductive activity of weakfishin this area Villoso1989, Taylor and Villoso1994!.

Captivespawning recordings: Captive weakfish held in a 1500L tankwere induced to spawnwith two injections of 1000 IU hCG/kgbody weight administered in the early afternoon on two succes- sivedays. Fish spawned during the eveningof the secondday of injections,Spawning activity was documentedon standardVHS tape with video IkegamiCCD camera, ICD 4224! and audio Edmund Scientific!input Connaughtonand Taylor 1996!, Field and captivesounds, staccato bursts of 6-10 individual pulses,were identical Connaughtonand Taylor 1996!. It was also determined that dominantfrequency and repetitionrate vary with temperatureand fish size Connaughtonet al.2000!.

Duringcourtship, only pairspawning was observed, though largergroups in largerenclosures might behavedifferently. Drumming activity was most often initiated afterthe first spawningevent, but basedon the timing of sound production and spawning in the field Taylor and Villoso 1994, Connaughton and Taylor 1995!this observation may be due to a tank effect. The number of drum- rning bursts per minute varied somewhat between males,but remained relatively constant for a givenmale for the durationof the evening'ssonic activity, i.e, number of burstsper minutedid not drop off astime passedafter a spawningevent. Sound production ceased prior to gameterelease, which was apparently synchronizedby body contact.

Ci'Oakei'expeflfllents Captivespawningrecordings: As above, Field caught Atlantic croaker were maintained in laboratory tanksand inducedto spawnfollowing hormone injections, and video/audiorecordings B&W CCD camera,OS-40D,WorldPrecision Instruments; model C21 hydrophone, CetaceanResearch Technology!were made. To date, only a singlesuccessful trial, involving one male and two females, hasbeen conducted. The courtship behavior of the croakerwas similar to that exhibitedby the weakfish:drumming began after the first spawningevent, was maintained for severalhours thereafter, and ceasedjust prior to gamete release.

Only the male produced courtship sounds,bursts of 1-3 pulses,with a mode of two pulses. Dominant frequency for the single recorded male 3 crn total length! was 300 Hz and the repetition rate of pulseswithin a burst was 5.4 Hz. Courtship sounds were lower in frequency and repetition ratethan fright responsesounds see below!. In addition,the numberof drummingbursts per

Proceedingsfrom the international I/I/orkshopon the Applications of PassiveAcoustics to Fisheries 22 minute decreasedsteadily following each spawning event, a behavioralcharacteristic not shared with weakfish Fig.1!.

Fright responserecordings: Fright responserecordings were made in a rectangular 1250L tank. Sound production was elicited by casting a shadowover the surface of the holding tank, or moving a dipnet throughthe water.Thirteen fish, ranging in total lengthfrom 22.5to 30 crnwere recorded, and both maleand fernale croaker called readily. The number of pulsesper burstfor fright response calls varied more widely that in courtship calls,ranging from 1-9,though the mode was still two. In contrast,the repetitionrate of pulseswithin a burstwas greater in fright responsecalls, ranging from 7.87to 33.56pulses/sec and expressinga meanof 18.09. Repetition rate was more variable in shorter bursts or 3 pulsesper burst! than in longer bursts Fig.2!. Evengiven that dominant frequency appearsto vary with fish size 50 to 540 Hz for 22,5to 29cm total length fish!, courtship sounds appear to havea lower dominant frequency approximately 100 Hz lower for a 33crnfish! Fig. 3!.

Discussion Soundproduction in weakfishand croakermay be involvedin the formationof spawningaggregations and/or attracting a mate,though becauseof the smalltank size,this could not be determined in our laboratory experiments Connaughton and Taylor 1996!. It may also play a role in female mate selection,since larger individuais of each speciesproduce a sound with a lower dominant frequency Connaughtonet al. 2000!. Though weakfishwill produce sounds if drawn to the surface when caught hook and line, or when removedfrom a tank into the air,we have never recorded a fright responsecall from weakfish like those so easilyelicited from Atlantic croaker. In-air'disturbance'callselicited from weakfish when they are removed from the water were identical to courtshipcalls except for havinga widerrange of pulsesin eachburst of sound Connaughtonet al. 2000!. In contrast,our data suggest that fright responseand courtship calls in croaker may be quite distinct in dominant frequency and repetition rate,though more data needs to be collected.

Acknowledgements Thiswork wassupported by the Wallop-BreauxSport Fishing Act with fundsadministered through the DelawareDepartment of NaturalResources and EnvironmentalControl and by in-housefunding provided by WashingtonCollege.

Literature Gted

Connaughton,M.A. and Taylor,M.H. 995!. Seasonaland daily cycles in sound production associated with spawning in the weakfish,Cynoscion regalis. Env. Biol. Fish.42,233-240.

Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 23 Connaug hton, M.A. and Taylor,M.H. 996!. Drumming,courtship, and spawning behavior in captive weakfish,Cynoscion regaiis. Copeia 1996,195-199.

Connaughton, M.A.,Taylor, M.H. and Fine,M. L 000!. Effectsof fish sizeand temperature on weakfish disturbance calls:implications for the mechanismof sound generation,J, Exp.Biol. 203, 1503- 1512.

Fish,J.F. and Cummings,W. C,972!. A 50-dB increasein sustainedambient noise from fish Cynoscion xanthurus!.J. Acoust. Soc, Arn. 52, 1266-1270.

Fish,M, P,and Mowbray,W.H. 970!. Sounds of western North Atlantic fishes.Baltimore: The Johns Hopkins Press,

Guest,W.C. and Lasswell,J, L. '!978!. A note on courtship behavior and sound production of red drum. Copeia 1978, 337-338.

Mok,H. K. and Gilmore,R.G. 983!, Analysisof soundproduction in estuarineaggregations of Pogoniascromis, Bairdiella chrysoura, and Cynoscionnebulosus Sciaenidae!.Bulletin of the Institute of Zoology, Academia Sinica22,157-186.

Saucier,M. H. and Baltz,D.M. 993!. Spawning site selection by spotted seatrout, Cynoscionnebulo- sus,and black drum, Pogoniascromis, in Louisiana.Env. Biol. Fish. 36, 257-272.

Tavolga,W.N. 964!. Soniccharacteristics and mechanismsin marine fishes.In Marine bio-acoustics, vol. 1 ed.W.N. Tavolga!, pp. 195-21I, New York:Pergamon Press.

Taylor,M. H.and Villoso, E.P. 994!. Dailyovarian and spawning cycles in weakfish.Trans. Am. Fish, Soc. 123, 9-14.

Tower, R.W, 908!. The production of sound in the drumfishes, the sea-robin and the toadfish. Ann. N.Y.Acad. Sci. 18, 149-180,

Villoso, E.P.989!. Reproductivebiology and environmental control of spawning cycle of weakfish, Cynoscionregalis Bloch and Schneider!in DelawareBay; University of Delaware,Newark, Delaware,

Proceedingsfrom the international Workshop on rhe Applications of PassiveAcoustics to Fisheries 24 Illustrationsand Diagrams

Figure 1. Croakercourtship sound production expressed as number of callsmin-' acrosstime, Valueswere deter- minedfor one minute out of every five recorded over the course of theevening. The solid vertical line represents the first spawning event 9:29PM! and the doublevertical line, the second0:29 PM!.

Figure2. Repetition rateplotted across number of pulsesper coll from sounds produced by male and femole croaker N=13! during fright response behaviors. The shaded block represents the repetition rate and number of pulses observedduring courtshipsound production.

Figure3. Dominantfrequency ofindividual sound pulses plotted across specimen total length from sounds producedby maleand femalecroaker N=13! during fright responsebehaviors. The shaded block represents thedomi- nantfrequency of callsmade by the single male 3 cm!during courtship sound production. Proceedingsfrom the internationalWorkshop on theApplications of PassiveAcoustics to Fisheries 25 ~Detection ~ and characterization ~ ofyellowfim andhluefm tuna using passive acousticaltechniques

Scott Allen' and David A. Demer'

'Scripps Institution of Oceanography [email protected]!

'NOAA/NMFS/SWFSC/FisheriesResources Division,8604 LaJolla ShoresDrive,La Jolla, CA 92037 [email protected]!

Introduction Underwatersounds generated by Thunnusalbacares and Thunnusthynnus were recorded and studied to explore the possibility of passive-acousticaldetection. Tuna vocalizationswere recorded at the MontereyBay Aquarium, Monterey, California, and Maricultura del Norte in Ensensada,Baja California,Mexico. At both locations,the most prevalent sounds associatedwith tuna were low-fre- quencypulses varying from 20 to 130Hz, lasting about 0.1 seconds, and usuallysingle and unan- swered Fig. 1!. A behavior similar to coughing was coincident with these sounds:the animal's mouth openedwide with its jaw bonesextended and its abdomenexpanded, then contracted abruptly,On one occasionin Mexico,this behaviorand associatednoise were simultaneously recorded Fig, 2!, Thecenter frequencies of thesevocalizations may vary as the resonantfrequencies of the tuna'sswim bladder,suggesting a passive-acousticalproxy for measuringthe sizeof tuna. Matched-filterand phase-differencetechniques were explored as means for automatingthe detection and bearing-estimation processes.

Conclusion Thisstudy shows that adultbluefin and yellowfin tuna, like many other fish, are capable of generat- ing sound,The acoustical signals are short -0.1 s!,narrow-bandwidth pulses of low frequency0- 130 Hz! and amplitude -105 dB re 1ItPa@ 1m!,

Observationsof thesefish suggestthat a coughingor yawningbehavior causes muscular contraction about the swim bladder and an associatedshort-duration sound pulse of narrow-bandwidth and low-frequencyand intensity,If the recordedsounds are generated by swimbladder resonance, then the sizeof the swim bladderdetermines the centerfrequency of the soundpulse. It is unknownwhether the tuna vocalizations are generated as a by-productof somebiological function such as clearing the gills, or an intentional form of communication.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 26 Acknowledgements Weare thankful to Dr.Rennie Holt, Director of the UnitedStates Antarctic Marine Living Resources Programand Dr.John Hunter, Head of the FisheriesResources Division, SWFSC, for providingthe laboratory and equipment resourcesnecessary to complete this study. We would also like to thank Dr. KennethBaldwin of the Universityof NewHampshire Center for OceanEngineering for aliowingS. Allen to conduct his Master'sThesis researchat SWFSC.Thanks also to Mr.Ted Dunn,founder of Maricultura Del Norte of Ensenada,Mexico for graciouslysupporting this effort with accessto his fish pens. Thanksfinally to Dr.Charles Farwell, the managerof pelagic displaysat the Monterey Bay Aquarium in Monterey, California.

ProceedingsFrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 27 Figure1. Bluefinvocalization recorded at Mariculturadel Norte, 18 November 2000 using two hydrophones a! and pressuretheir powerlevelis spectral105d8 densireties1 mP, b!. Signals were low-pass fiitered OrderFigure0 Butterworth,2. Afc=600tuna vocalizing Hz!,bluefin EstimatedatVariculturasound

del NorteEnsenada, During the vocalization,the animal'smouth opened wide with itsj aw bone» extendedandits abdomen expanded,then con- tractedabruptly

Proceecfr'ngsfrom the international ilYorkshopon the Apph'cationsof PassiveAcoustics to Fisheries 28 AcousticCompetition in the Gulf Toadfish Opsanusbeta: CrepuscularChanges and AcousticTagging

Michael L. Fine' and Robert F.Thorson'

'Department of Biology,Virginia Commonwealth University,Richmond, VA 23284-2012 'Presentaddress:133 Mockingbird Rd.,Tavernier, FL 33070

We quantified crepuscular variation in the emission rate and call properties of the boatwhistle advertisement call of Gulf toadfish Opsanusbeta from a field recording of a natural population of nesting malesin the Florida Keys.Their calls are more variable and complex than previously reported Fig.1!. A call typically starts with a grunt followed by one to five tonal boop notes typically two or three! and lastsfor over a second.The first boop is considerably longer than later ones,and inter- valsbetween boops are relativelyconstant until the final interval,which approximately doubles in duration.Positions of fish arefixed for long periods,and callsare sufficiently variable that we could discern individual callers in field recordings Fig. 1!. Calling rate increasesafter sunset when males tend to produce shorter calls with fewer notes Fig.2!. Analysisby number of notes per call indicates some individuals decreasethe number of initial grunts and the duration of the first note, but most of the decreaseresults from fewer notes, To our knowledge this sort of call plasticity has not beendemonstrated before in fishes.We suggest that call shorteninglowers the chancesof overlapping callsof other malesand that the smallamount of time actuallyspent producing sound total on time! is an adaptation to prevent fatigue in sonic musclesadapted for speed but not endurance.

Anomalous boatwhistles contain a short duration grunt embedded in the tonal portion of the boop or between an introductory grunt and the boop Fig,3b, c!. Embeddedgrunts have sound pressure levelsand frequency spectra that correspondwith thoseof recognizedneighbors, i.e. we areable to identifyindividuals based on frequencyspectrum of their grunts Fig.4!.Wetherefore suggest that onefish is gruntingduring another'scall, a phenomenonhere termed acoustic tagging. Snapsof nearbypistol shrimp may aiso be tagged,and chainsof tags involvingmore than two fish occur Fig, 5!. The stimulus to tag is a relatively intense sound with a rapid rise time, and tags are generally pro- ducedwithin 100ms of a triggerstimulus. Time betweenthe triggerand the tag decreaseswith increasedtrigger amplitude. Tagging is distinct from increasedcalling in responseto natural calls or stimulatoryplaybacks since calls rarely overlap other callsor playbacks.Tagging is not generally reciprocal between fish suggesting parallelsto dominance displays.

Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 29 Illustrationsand Diagrams

Rme1IOO sm/ dls!

I OHz-Is

Time11OO mvI divs

I kHxte mms

Rase110ll ms I divI

I kHzs

IOO Time IOO mv I dlv! da / ITsII

TimeI OOI ms I dlv1 T IsIS9IS O -TO

Fig.1, Sonagrams and oscillograms from fi ve indi vidual Opsanus be! a.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 30 Illustrationsand Diagrams

1 kHz 800 600 400 200

1 kHz 800 600

400 200 1 Time sec!

Fig2. Sonagramsfrom 4-, 3-,2- and 1-hoopcalls from an individual Opsanusbeta.

Proceedingsfrom the International Workshop on the Applications of PassiveAcoustics to Fisheries 31 Illustrationsand Diagrams

1 kHz

800 600 400 200 6 8182 83 1. see I' div

800

600

400

200

100

ZOFSO

-100

Fig.3.Sounds ofOpsanus betaillustrating acoustic tagging. a! A typicalboatwhistle with aninitial grunt G!,a long tonalhoop Bl andtwo shorter hoops B2 and B3!, b! Sonagram and c!oscillogram ofa boatwhistletagged by anotherfish. The T marksthe tag, which has lower frequency energy and greater ampli tude than the boatwhistle.

Proceedingsfrom the International VYorkshopon the Applications of PassiveAcoustics to Fisheries 32 e cl U t

I -10 ~ -15 A -20 J -25 F2 k -35 F4 ' e p -r0 T

100 200 300 400 500 600 700 800 Peak Frequency Hg Fig,4, Plot of peakamplitude in dBagainst the frequency of peakamplitude from grunt spectra for four toadfish recordedat weeklyintervals.

l00

%FS 0 -50

-100 l sec /div l 00

%FS 0 -50

- l 00 50 ms /div

%FS 0

-50 - l 00 S F3 F2 F l l00 ms i div

Fig.5 Tagsof shrimpsnaps. a! oscillogram of a pistolshrim p snaptagged by fish I witha latencyof 41 msshown in realtime. b! Sameselection expanded. c! Chainof tagsinitiated by a shrimpsnap thatis taggedby fish 3, Fish 3's gruntis then tagged by fish2, whoin turnis tagged by fish 1.

Proceedingsfrom the international I/I/orkshopon the Applications of PassiveAcoustics to Fisheries 33 ~ ~ ~ ~ Passive Acoustic Field Research on Atlantic Cod, Gadus morhua L. in Canada

Susan B. Fudge' and George A. Rose'

'FisheriesConservation Chair, Fisheries and Marine Institute, Memorial University of Newfoundland, 155 Ridge Road, PO Box 4920, St. John' s, NF Canada, Al C 5R3 [email protected],mun.ca.

'SeniorChair of FisheriesConservation, Fisheries and MarineInstitute, MemorialUniversity of Newfoundland,155Ridge Road,PO Box 4920, St.John' s, NF Canada,A1C 5R3 groseCicaribou.mi.mun.ca.

Introduction

The Atlantic cod is a very important commercialfish in Newfoundland and Atlantic Canadaand has beena partof the culturefor centuries.In the pastten years,codstocks have been drastically depleted. In Newfoundland waters, cod is found from the coast to the continental shelf in water temperaturesranging from approximately-0.5 'C to 8.5'C, They are broadcastspawners and typically spawnin largeaggregations Robichaud,2002!. The spawning season typically occurs in the spring but variesby area and is influenced by environmental factors, such as temperature Scott and Scott,1988!. Spawning begins in the north as early as Februaryand ends in the south as tate as December,The depth at whichspawning occurs varies among stocks; some may spawn in wateras shallowas 20 m,while othersat depthsover 300 m Rose,1993!. Differences in spawningbehaviours amongsub-stocks and amongages and sexeshave been reported Robichaud,2002!, Laboratory studieshave shown that cod haveelaborate courtship behaviours with malesbeing very territorial and more aggressivemales having the most successat spawning. Cod are also known to detect and producesound and this observationhas long beenrecognized by Iab experiments e.g. Brawn, 1961!.This study is the first attemptin Canadato documentthe soundsmade during spawning and to relate them to spawning behaviour in order to link active and passiveacoustic researchin behav- ioura I field studies.

Previous and future research on Atlantic cod behaviour

Two of the largestspawning components of Atlantic cod in Newfoundland waters have been studied usingactive acoustics for severalyears. These include Placentia Bay, located on the southcoast of Newfoundland NAFO regulatory area 3Ps!, and Trinity Bay, located on the north eastcoast NAFO regulatoryarea 3L!. Annual acoustic surveys using SIMRAD EK 500 echosounders, along with the analysesof the data using FASIT Fisheries Assessment and SpeciesIdentification Tool! Lefeuvre et

Proceedingsfrom the International 5'orkshop on the Applications of PassiveAcoustics to Fisheries 34 al.,2000!have provided insights into stockmigrations and spawning behaviours, The echograrn in Figure1 isfrom April 2000in PlacentiaBay, Newfoundland, showing some of the pelagicbehaviour easilyobserved using an echosounder. Cod in this areahave a peakspawning period between April andJune. This spawning aggregation was found in a trench,over 300 m deep.The image in the bot- torn corneris an enlargementof the echograrnwhere single cod targets white arrow!are resolved.

Theuse of activeacoustics has lead to observationsof different spawning aggregation structures, Figure2 isan echogramof spawningcolumns observed in shallowwaters of PlacentiaBay in 1997 at a depth of approximately 50 m Rose,1993!. In section A, severalcolumns are shown. Section 8 is an enlargementof one of thesecolumns, which extends approximately 20 m off the oceanfloor.

Throughouttheir range,cod occurin distinctstocks as well assub-stocks, and spawningbehaviour withinspecific sub-stocks isof interest.Sonar tagging studies have been conducted to investigate the horningability of Atlanticcod to specificspawning grounds. Long-term sonar transmitting tags LotekCAFT16 3 AcousticTransmitters! were implanted in femaleand male cod at a spawning groundin PlacentiaBay, Newfoundland in April 1998. Homing of codback to thespawning ground from whichthey were taken was observed, Approximately 50'/o of the tagged cod returnedto the same spawning ground capture site! in subsequentyears and 259oof the tagged cod returned 3 years in a row Robichaudand Rose,2001!. This study provides some of the first direct evidence that cod undertakinglong-distance feecting migrations may home to a specificspawning location in consecutiveyears. Present tagging work that has begun this year also will involve the identification of distinctspawning populations using acoustic surveys; cod havebeen released within their "home"populations as well aswithin othergroups. Results of this studyhope to providevaluable insight into the Atlantic cod's horning properties,

Usingactive acoustics in surveysand sonartagging studies, we havelearned a greatdeal about cod spawningaggregations and migratorybehaviour. As spawning is the first steptowards recruitment andrebuilding cod stocks, there is a continuinginterest in thespecific behaviour of spawning. Brawn961! documented many interesting featuresof cod spawning behaviour.Cod are known to havespecific social behaviours related to spawning,Brawn 961! observeddistinct courtship behavioursperformed by malestoward females, as well asaggressive behaviour of malestoward males.Both sexes in cod havebeen observed to producesound, although it is the maleswhose soundproduction is thought to playan importantrole in spawning,such as attracting females and holdingterritories Brawn, 1961!. In cod,the drummingmuscles surrounding the swimbladder are thought to be related to sound production.

Presentfield studieswill observethe acousticproperties of spawningaggregations over two spawningseasons. These studies are interested in boththe productionand reception of soundby cod, its role in spawning behaviour,and alsothe influence of ambient noise in the ocean environment on these behaviours.We have chosentwo main researchareas, which have been studied for the pastnumber of yearsusing active acoustics and sonar tracking. Placentia Bay and Trinity Bay bothhave relatively large coastal spawning populations. However, Placentia Bay is becoming increasinglyindustrialized while Trinity Bay is not. With use of a smallvessel speciaily equipped for

Proceedingsfrom the International Workshopon the Applications of Passive Acousticsto Fisheries 35 the work, cod spawning aggregationswill be located using a BiosonicsDE 70 kHz echosounder with digital data storage.Once located sounds from the aggregation are detected,they will be recorded using a hydrophone ITC8212! with a StanfordResearch System pre-amplifier model SR560!.Data will be in the form of WAVfiles and stored on a harddrive of a lap-top computer and analyzed using Avisoft SASLabPro software.Video recordings will be made using an underwater video camera J.W. FishersMFG. Inc., TOV-1!. A parallelstudy will be conducted on fish from the same stocks kept in the lab at the aquaculture facility at Memorial Universityof Newfoundland,

Summary This study is the first of its kind in Canada,and is attempting to document the sounds that cod make during spawning at seaand to relate these to spawning behaviour.The work attempts to link active acoustic researchwith passiveacoustics and to use real-time video to study cod spawning behaviour.From past acoustic research,we have learned much about the state of cod stocks,spawning aggregations, migrations,and homing. With the addition of passiveacoustic tools, we hope to learn more about the spawning behaviour of individual cod.

Acknowledgments Severalpeople were instrumental in past and present studies,We would like to thank Dave Robichaud,Wade Hiscock,Matt Windle,the crewsof the CCGSTeleost and CCGSShamook. Danny Boyceof the Aquaculture Facilityat Memorial Universityand all the participants and sponsors of the international Workshop of Passive Acoustics in Fisheries.

References

Brawn, Vivien M. 1961. Aggressive behaviour in the cod Gadus callarias L.!. Behaviour 18: 108-145.

Brawn, Vivien M. 1961. Reproductive behaviour of cod Gadus callari as L.!. Behaviour 18: 177-198.

Brawn, Vivien M. 1961. Sound production by the cod Gadus callarias L!, Behaviour 18: 239-245.

Chapman,CJ, and A, D, Hawkins.1973.A hearing study in the cod, Gadusmorhua L.Journal of Comparative Physiology 85: 147-167,

Lefeuvre,P., G.A. Rose, R. Gosine, R. Hale, W, Pearson,and R,Khan. 2000. Acoustic speciesidentification in the northwest Atlantic using digital image processing.Fisheries Research 4!: 137-147

Nordeide,J,T, and E,Kjellsby. 1999. Sound from cod at their spawning grounds, lCESJournal of Marine Science. 56:326-332,

Robichaud,D. 2002.Homing, population structure and managementof cod, with emphasis on cod

Proceedingsfrom the International Mlorkshopon the Applications of PassiveAcoustics to Fisheries 36 spawning at Bar Haven in PlacentiaBay, Newfoundland, Ph,D. thesis. Biology Department, Memorial University of Newfoundland.

Rose,G.A. 1993.Cod spawning on a migrationhighway in the north-westAtlantic. Nature 366:458-461.

Scott W.B.,and M.G.Scott. 1988,Atlantic Fishesof Canada.University of Toronto Press,Toronto.

Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 37 Figure'i. Echograrnof a spawningcod aggregation in PfacentiaBay, Newfoundland 2001.

Figure2: Codspawning column in PlacentiaBay in t 997.

Pmceedings from the international 5'ori:shop on the Appiicationsof PassiveAcoustics to Fisheries 38 ~ Passive~ ~~ Acoustic ~ Transects: Nlating ~ Calls and Spawning Ecologyin EastFlorida Sciaenids

R, Grant Gilrnore, Jr., Ph.D.

Dynarnac Corporation,Mail Code: DYN-E,Kennedy Space Center, FL 32899,USA. rg g ilmorejOaol.corn

Introduction

HistoricalAcoustic Work with SciaenidFishes: Sciaenid fishes have been known to produce sound for centuries Aristotle,1910;Dufosse, 1874a,b! and the associationof sciaenidsounds with spawning hasbeen knownnearly as long Darwin,1874; Goode, 1887!. For hundreds of yearsthe Chinese haveisolated sciaenid spawning sites from their watercraft by listeningto drummingsounds ema- natingfrom the waterthrough the hull of their boats HanLing Wu, Shanghai Fisheries Institute, pers.comm.!. The isolation of sciaenidspawning sites using underwater technology is recentand dependent on the availability of underwater transducers,hydrophones, and acoustic recordersused to accessand studyunderwater sounds Fishand Mowbray1970!. Hydrophone tape recordingsof vocalizationsproduced by largesciaenid aggregations during spawning was pioneered by Dobrin 947!, Dijkgraaf 947, 1949!, Knudsen et al, 948!, Protasov and Aronov 960!, Schneider and Hasler 960!,Tavolga 960, 1981!,Fish and Mowbray 970!, Fishand Cummings972!.

Thefirst isolationand descriptionof soniferoussciaenid aggregations using mobile hydrophones moving along a sound transect at spawning sites was conducted by Takemuraet al. 978!, Mok and Gilrnore 983! and Qi et al. 984!, A portable hydrophone and recording systemwas carried via a boat from one siteto anotheralong a measuredtransect with recordingsmade along a presetgrid or in a linearseries Mokand Gilmore1983; Gilmore 1994, 1996, 2002!. Recordings were made for 30 300seconds at eachsite depending on transectlength. Recorded sounds were verified by recording capturedspecimens identified to speciesand documenting specific sound types through sonographic analyses.This technique allowed spatial-temporalisolation and identification of species- specificsounds produced by sciaenidfishes, particularly under conditions of high soundattenua- tion for large group sounds low frequency high intensity sounds!.

Using detailed sonographic analysesof field recordings made on transects Mok and Gilmore 983! describedthe characteristicsounds of blackdrum, Pogonias cromis, spotted sea trout, Cynoscion neb- ulosusand silver perch, Bairdieliachrysoura, Subsequent to these observationsconsiderable additional work has been done on sound characterizationin these speciesas well as the weakfish,C. regalis and the red drum, Sciaenopsocellata. Passive acoustic transect techniques have been used by several investigatorsto isolate spawning sciaenidgroups in the field Sausierand Baltz,1992, 1993;Connaughton and Taylor,1994, 1995; Luczkovich et al., 1999,2000!.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 39 RecentEast Florida research 1990-2002:Over the pasttwelve years the valueof passiveacoustic studies in determining spatial and temporal spawning activity in sciaenidshas increased. Eastcentral Florida studies have been supported by the Florida Fishand Wildlife ConservationCommission, U.S. GeologicalSurvey, National Aeronautics and SpaceAdministration, Canaveral National Seashore and NOAA/National Marine FisheriesService. The major objectives of these studies have been to develop newtechniques and technologiesto allow realtime continuousmonitoring of soniferousaquat- ic organisms.This inciuded a prototypeneural network to identifyspecies specific sounds Lin 1996!,and remotelydeployed underwater computer systems HBOI ALMS; NASA PAMS! with hydrophonesand physical sensors for environmentalparameters to allow association of physical oceanography with acoustic activity.

Futureacoustic research at theKennedy Space Center: The iongterm objectivesof this workat the KennedySpace Center is to developan acousticand sensorarray that will allow continuousmonitoring of biotic acousticactivity in associationwith intra andinterspecific interactions as well ascli- rnaticand oceanographicphenomena, An experimentalacoustic arena is beingdeveloped in the marineprotected areas within the securezone of the NASAand U.S, Air Forcelaunch complex at Cape Canaveral,

Function of Sound Production in Sciaenids Themost predictable and robust sounds produced by manyfishes are those associated with reproduction. As in many soniferous animals,it is the male that must attract a mate and induce her to donateeggs for fertilization,and, therefore, it isoften only the male that produces sound. Large choralaggregations of malesciaenid species are formed by spottedseatrout, weakfish, red drum andsilver perch specifically to attractfemales with whichto spawn.Since these male choral aggregations contributeno significantresources required by femalesexcept the malesthemselves no malepaternal care, no food,or nestsites! they areappropriately called seatrout "ieks",such as those formedby aggregative birds and amphibians strictly for thepurpose of reproduction Hoglund and Alatalo1995!. A lekis an arena to whichfemales come and on which most of the matingoccurs. An arenais a siteon whichseveral males aggregate but doesnot form the habitat normally used by the speciesfor other activitiessuch as feeding. Sciaenid leks are seasonal and are associated with a wide varietyof environmentalparameters that arefavorable for egg,larval and adult survival.The acousticproperties of lek sitesare undoubtedly favorable for matingcall transmission and must havespecific acoustic properties. Although many sciaenid spawning sites have been isolated to date,their acousticproperties have not beenstudied in detail Mokand Gilrnore, 1983; Saucier et. al, 1992,Saucier and Baltz, 1993, Luczkovich et al.,1999; Gilmore 2002!. Aggregative calling only occurs at theappropriate time for spawning,facilitating successful mating, egg fertilization, egg/larval dispersal and survival,

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 40 Sciaenid Sound Production Niechanisrns The most robust and energetic sciaenid sounds are produced by sonic musclesindirectly or directly vibratingthe membraneof the gasbladder. When a freshlycaptured, recently calling, male seatrout is dissected,the bright red sonicmuscles surrounding the gasbladder can be easilydifferentiated from the exterioriateral body muscles.The muscle vibratory rate is directlyassociated with the fun- damentalfrequency of the characteristicseatrout call producedby the gasbladder.

Mostof the 1,200species in this family producesound usingsonic muscles associated with the gas bladder.Using the speciesspecific muscle contraction rates and the gas bladder shape sciaenids producediagnostic sounds that canbe usedto identify specieswithin the family Mokand Gilmore ! 983!,as has been demonstrated in amphibiansand birds.The characteristic shape of the sciaenid gasbladder is so conservativethat it hasbeen used as one of the primarycharacters to classifysci- aenids and to determine their phyletic relationships Chu 1963;Chao 1978,1986!.

Classification of Sciaenid Sounds

Figure2 illustrate the diagnostic mating calls of sciaenids known to spawn in the Indian River Lagoon system of east central Florida.

SciaenidAcoustic and SpawningEcology: When and Where do Sciaenids ProduceSound? Mok and Gilmore 983! demonstrated that sciaenid sound production was specifically associated with crepuscularand nocturnalcourtship and spawningactivities. Pelagic eggs and larvaeof the spottedseatrout were collected with planktonnets at spawningsites during vocalization periods Mok and Gilrnore, 1983; Alshuth and Gilrnore, 1993, 1994, 1995!, These same studies of soniferous spawning aggregations have demonstrated long-term spawning site fidelity, with the principal spawning sites identified by Mok and Gilmore 983! being used for over twenty years Gilmore, 1994, 1996, 2002!.

Asmale spotted seatrout could be recognizedby distinctivecrepuscular calls their presenceor absencefrom specific locations could be determined and the percent occurrenceof calls at all acoustic listening sites derived. In addition, the approximate size of the calling group could be esti- rnated based upon sound intensity dB level, re 1 IiPa! and group sizeestimates using a three part scale:1- smallgroup or individualcallers; 2 - moderategroups of severaltens of callers;and 3- a largegroup of what appearto be hundredsof simultaneouscallers. Unfortunately, mixed species chorusbehaviors were cornrnon with Ariusfelis and Bairdiellachrysoura joining in with spotted seatrout calls,therefore, elevating site specific sound intensities and maskingseatrout numbers basedon soundintensity. The percent occurrence of spottedseatrout calls at a siteor time periodis the most objective data used to define site and period use by seatrout leks. However,Gilrnore 994! found that spatialand temporal distributions of the estimatedgroup size, egg and larval abundancein the water columnand percentoccurrence of callingtrout werehighly correlated r =

Proceedingsfrom the international IVorkshop on the Applications of PassiveAcoustics to Fisheries 41 0,92to 0.98at u= 0.05!.This indicates that group sizeestimates were a useful,independently derivedvariable that could be usedto verifycalling trout distributions and relative use of specific sitesor particulartimes of the year.These two datatypes have been used to isolatespawning times and locations,

Seasonalmating calls were directly associated with primaryspawning activity in eastcentral Florida sciaenids.Figure 4 summarizestheir seasonalcall pattern at this latitude basedon over 300 acoustic transects between 1978 and 2002.

Spatialdistribution of sciaenidspawning cal/s: All soniferousspawning populations of sciaenidsin the upperBanana River Lagoon, a lagoonassociated with the IndianRiver Lagoon system, within the protectedwaters of the KennedySpace Center have been mapped, Spawning sites are utilized only fromsunset to midnightduring the spawningperiod with greater call activity on newand full moonphases. Some sites within the IndianRiver Lagoon system have been known as favored spawningsites with mating calls having been recorded from these sites for over20 years. Figure 5 representsprimary call sitesfor all sciaenidsknown to spawnin the upperBanana River Lagoon basinnorth of the NASACauseway at the KennedySpace Center.

FutureTechnology Developments at KSCRelative to Acousticstudies of SciaenidFishes Oncelocations and periods of acousticactivity and spawning have been isolated as they have at the KennedySpace Center, then a numberof basicquestions and hypothesescan be addressedrelative to the evolutionary significance of sound production in sciaenids and other soniferousfishes. Examples are;

1, Doessciaenid sound production increase the probabilityof predationmortality? 2. Whatare the energeticcosts of sonifery? 3. Howdoes sciaenid foraging behavior relate to spawningand soundproduction and arethere sexualdifferences in foragingbehavior as a resultof differencesin matingbehavior, acoustic energetics? 4. Whatare the benefitsof soniferyto spawningaggregations? Withthe installationof permanentacoustic arrays, portable acoustic systems, roving robotic acousticplatforms and physicalsensor arrays we believeit will be possibleto addressdetailed researchobjectives that will finally unravel the intimatemating, foraging and predatory escape behaviorsof regional estuarine sciaenid communities,

Acknowtedgements SensorWeb pod deployments{developed by KevinDelin, NASA/JPL, Pasadena, CA! and our NASA/KSCPAMS Portable Acoustic Monitoring System! being deployedby the Cleliasubmarine during a NOAAOE project August 2001.

Proceedingsfrom the internationai I/I/orkshopon the Applications of PassiveAcoustics to Fisheries 42 Literature Cited Alshuth,S. and R.G. Gifmore. 1993. Egg identification, early larval development and ecology of the spottedseatrout, Cynoscion nebulosus C. Pisces:Sciaenidae!. ICES C.M. 1993/G 28, Dern. Fish Com; 18 PP.

Alshuth,S. and R.G. Gilmore. 1994. Salinity and temperature tolerance limits for larvalspotted seatrout,Cynoscion nebulosus C. Pisces:Sciaenidae!, ICES C.M. 1994/L:17, Biol. Oceanogr. Cttee., 19 PP.

Aishuth,S. and R,G.Gilmore. 1995. Egg and earlylarval characteristics of Pogoniascromis, Bairdielia chrysoura,andCynoscion nebulosus Pisces: Sciaenidae!, from the IndianRiver Lagoon, Florida. ICES C.M. 1995/L17,Biol. Oceanogr. Cttee. 21 pp,

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Chao,L.N. 1978. A basisfor classifyingwestern Atlantic sciaenidae Teleostei: Perciformes!. NOAA Tech. Rept. NMFS Circ. 415.

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Connaughton,M,A, and M.H.Taylor. 1994, Seasonal cycles in the sonic musclesof the weakfish, Cynoscion regalis. Fish, Bull. 92: 697-703.

Connaughton,M.A.and M.H,Taylor.1995. Seasonal and daily cyclesin soundproduction associated with spawningin the weakfish,Cynoscion regalis. Envir. Biol. Fish.42: 233-240.

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Dufosse,A.1874b. Rescherches surles bruts et lessons expressifs que font entendreles poissons d'Europeet surles organes producteurs de cesphenomenes acoustiques ainsi que sur les appareils

Proceedings rom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 43 de I'auditionde plusieursde cesanimaux. Annafes des Sci.Naturelles ser 5,20; 134 pp.

Fish,J.F. and WC. Cummings, 1972. A 50-dBincrease in sustained ambient noise from fish Cynoscion xanthurus!. J. Acoust. Soc. Amer. 52: 1266-1270.

Fish,M,P, and W.H. Mowbray. 1970. Sounds of westernNorth Atlantic fishes. The Johns Hopkins Press, Baltimore,

Gilmore,R,G, Jr, 1994. Environmental parameters associated with spawning,larval dispersal and earlylife history of thespotted seatrout, Cynoscion nebulosus Cuvier!, Final Program Rev., Contract No.LCD 347. Mar. Res. Inst., Fla. Dept. Environ. Protection, St. Petersburg, Fla,

Gilrnore,R G.,Jr.1996. Isolation of spawninggroups of spottedseatrout, Cynoscion nebulosus, using passivehydroacoustic methodologies. Final Report,21 November 1996,12 pp., Fla. Dept, Environ. Protection,Mar. Res. Inst., St. Petersburg, Fla. Subcontract to Dr.Roy Crabtree, Principal Investigator, FMRIstudy entitled: The reproductive biology of spottedseatrout, Cynoscion nebulosus, in the Indian River Lagoon.

Gilmore,R.G, Jr.. 2000. Spawning site fidelity, classification of spawningenvironments and evolu- tionarystable strategies: Serranids versus Sciaenids. Abstract! In Session54: Fish Aggregation Symposium.80th Annual Meeting Arn.Soc. Ichthy. And Herp.,La Paz,Mexico, June 14-20,2000.

Gilmore,R G,Jr..2002. Sound production and communication in the spottedseatrout. Chapter 11. pp.177-195, in Biology of the Spotted Seatrout,S.A. Bortone, ed. CRCPress, Boca Raton,

Goode,G. B. 1887, American fishes: a populartreatise upon the gameand food fishesof North Americawith specialreference to habitsand methodsof capture.L.C. Page Co,, Boston.

Hoglund,J. and R.V.Alatalo. 1995. Leks. Princeton Univ. Press.248 pp.

Knudsen,V.O., R.S. Alfred and J.W, Ernling, 1948. Underwater ambient noise. J. Mar. Res., Vol. 7:410- 429.

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Luczkovich,JJMW Sprague,SEJohnson and R C.Pullinger. 1999. Delimiting spawning areas of weakfish,Cynoscion regalis family Sciaenidae!, in Pamlico Sound, North Carolina usign passive hydroacousticsurveys. Bioacoustics 10: 143-160,

Luczkovich,J J., H J.Daniel Ill, M. Hutchinson, T.Jenkins, S.E. Johnson, R.C. Pullinger and M.W. Sprague. 2000.Sounds of sexand death in the sea:bottlenose dolphin whistles suppress mating choruses of silver perch. Bioacoustics 10. 323-334.

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Proceedingsfrom the lnternationo/Workshop an the Applicationsof PassiveAcoustics to Fisheries 44 Qi, M., S.Zhang and Z. Song. 1984, Studieson the aggregate sound production of most speciesof croaker sciaenoidfishes! in BohaiSea, Yellow Sea and EastChina Sea. Studia Marina Sinica, Peking, 21: 253-264,

Saucier,lVi.H. and D,M,Baltz. 1992. Hydrophone identification of spawningsites of spottedseatrout Cynoscionnebulosus Osteichthys:Sciaenidae! near Charleston,South Carolina.N.E. Gulf Sci.12!: 141-145.

Saucier,M,H. and D.M.Baltz. 1993. Spawning site selectionby spottedseatrout, Cynoscion nebulosus and black drum, Pogoniascromis, in Louisiana.Env. Biol. Fishes36: 257-272.

Schneider,H, and A.D.Hasler 1960. Laute and luerzeugungbeirn susswassertrommier Aplodinotus grunniensRafinesque Scianenidae, Pisces!, Zeitschr. Vergl. Physiol., Vol. 43: 499-517.

Takemura, A, T.Takita and K. Mizue. 1978. Studies on the underwater sound - Vll: Underwater calls of the Japanesemarine drum fishes Sciaenidae!.Bull.Jap. Soc. Sci. Fish.44;121-125.

Tavolga,W, N, 'l 960.Sound production ancf underwater communication in fishes.pp. 93-136, in AnimalSounds and Communication,Lanyon, W.E. and W.N. Tavolga, eds., AIBS 7.

Tavolga,W.N., A,N, Popper and R.R.Fay. eds!. 1981. Hearing and soundcommunication in fishes. Springer Verlag, N,Y.;pp 395-425

Proceedingsfrom the International iiyorkshopon the Applications of PassiveAcoustics to Fisheries 45 Fig.I. Representativesciaenidinternal anatomy revealing the gas b!adder and sonic muscles of a maleweakfish, Cynoscion regalis.

Proceedingsfram the riternatianal l4'orkshopon the Applications of PctssiveAcoustics to Fisheries Fig.2.Energy distribution patterns associated with hormonicfrequency bands ond fundamental frequenciesare speciesspeci fic and wereused to train a neurainetwork to recognizesci aeni d caiis Lin 1996!. IllLIStl'8tIOAScIACI DlcIQMMS

Figure4. Croakercourtshi p soundproduction expressedas numberof callsmin- t acrosstime. Valueswere deter- minedfor oneminute out of everyfive recorded over the course of theevening. The solid vertical lirie represents the first spawning event 929ph4and thedouble vertical line,thesecond 'l029piVl!.

Figure 5

Proceedingsfrom the international ifYorkshopon the App!icat onsof PassiveAcoustics to Fisheries 48 TheUse of Passive Acoustics toIdentify a Haddock Spawning Area

Anthony D. Hawkins

FRSMarine Laboratory,PO Box 101,Victoria Road,Torry, Aberdeen AB11 9DB,Scotland, UK. g reenseasObtopenworld.corn

Introduction

The haddock is an important food Fish,widely distributed throughout the deeper shelf waters of the North Atlantic.lt is very heavilyfished and in someareas is consideredto be exploitedbeyond safe biologicallimits. Fisheriesmanagement measures have included the closureof spawningareas Waiwood & Buzet,1989!. Haddockgather together close to the seabedto spawn Boudreau, 1992!. Fertilization is external and the pelagiceggs hatch near the seasurface. The larvae drift in the upperpart of the watercolumn before the youngfish movedown to the seabed.There is very little detailedinformation, however, on wherehaddock spawn. The iocation of the spawninggrounds hasto be inferredeither from catchesof matureFish, or fromthe distributionof pelagiceggs. Haddock are generally believed to spawn offshore at depths of 200-500m or even deeper Solerndalet al, 'l997!,but oralevidence from Fishermensuggests that in someareas haddock may spawn inshore Ames, 1998!.

Likeother membersof the codfamily Gadidae!,the haddockis a noisyFish. The male produces a diversityof soundsover the spawningseason, with distinctivesounds associated with particular behaviouralacts Hawkinsand Amorim,2000!.This behaviour offers the opportunityto detect the presenceof spawning Fishsimply by listening for sounds. A searchwas therefore carried out in coastalwaters by listeningfor the characteristicsounds of haddock.By this meansan aggregation of spawninghaddock was located at the upperend of Balsfjord,a sub-arcticfjord in Northern Norway.

Aquarium Observationson SpawningHaddock Spawning of captive haddock was observed in a 10 rn diameter annular aquarium tank at the FRS Marine Laboratory Aberdeen. Waterdepth was 1.5 rn and the water temperature was maintained at 8 'C.The Fish were observed from aboveby meansof a lowiight levelTV camera and their behaviour recorded on a time-lapsevideo tape recorder.

The sounds of the fish were detected with an omni-directional broad-band hydrophone ITC,605'C!, amplified StanfordSR560 pre-amplifier, bandwidth 30 Hzto 10kHz!, sampled at 8 kHzand recorded

Proceedingsfrom the InternationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 49 directlyas WAV files on the harddisk of a lap-topcomputer by meansof AvisoftRecorder. Sound analysis was performed with Avisoft SASLab Pro.

Inthe aquarium, individual fernale haddock spawned repeatedily over several weeks. Spawning was accomplishedthrough a closespawning embrace, and precededby elaboratecourtship behaviour. Soundswere recorded in the aquariumfrom maleand female haddock, and from juveniles. However,during the spawningperiod sounds were predominantly made by the malefish.

Haddocksounds have been described as a seriesof'knocks' Hawkins& Chapman, 1966!, repeated regularlyat differentrates. It hassince become apparent that eachknock can be subdividedinto two short,low-frequency pulses of sound,spaced closely together Hawkins& Amorirn,2000!.

Theindividual knocks produced by malefish were regularly repeated at a rangeof differentrates, dependingon the behaviourof thefish. Short sequences of repeated knocks were emitted during agonisticencounters, At spawningtime, male fish producedmuch longer sequences, lasting from severalseconds to severalminutes, the knocksbeing procfuced at intervalsvarying from 500ms to 30 ms. At the very fastest rates,with intervals of lessthan 50 ms,the soundswere heard as a contin- uoushumming. Different behavioural acts leading up to the spawningembrace were associated with differentrepetition rates. This rich diversity of soundsproduced by the male haddock appears to be characteristicof this species.

Malehaddock showed a distinctivesolitary display. Dominant males adopted a characteristicpattern of pigmentation,occupied a favouredarea and showed a characteristicpattern of rnovernent, moving in tight circles or a figure of eight. During this behaviour the male uttered an almost contin- uoustrain of regularlyrepeated knocks repeated at intervalsof between140 and 60 ms Figure1!. Duringthe spawningseason males spent much of their time in solitarydisplay 9 h out of 24,750/0at night!, interrupting the display only when other fish entered their territories.

Differencesbetween the soundsof individualmale haddock were analysed by measurementson the waveforrnor through waveletanalysis see Wood, these proceedings!. In mostinstances the knockswere composed of two pulsesseparated by intervalsof 10-20ms. The two pulsesoften dif- feredin frequency,the first beinghigher than the second, Within a givencall, or fromday to day, therewas little variationin the waveformfor an individualfish. Frommonth to month,however, there wasa significantchange in the detailof the waveform,though the doublepulse structure was usually retained. There were often striking differencesbetween the soundsof individual males Figure 2!.

Thecharacteristic sounds described from haddockin the aquariumprovided dear criteriafor the locationof spawningmale haddock in the sea.The short low frequencysounds below 1 kHz!, madeup of two pulsesseparated by intervalsof 10- 20 ms,regularly repeated at intervalsof 300- 30 ms,often for morethan severalseconds, provided unequivocal evidence of the presenceof haddock,Moreover, changes in therepetition rate of thesounds were indicative of differentstages in the behaviourof the haddock.The sounds were quite different from thosedescribed for other gadoid fish Hawkins & Rasmussen 978!.

Proceedingsfrom the InternationalWorkshop on the Appiicationsof PassiveAcoustics to Fisheries 50 Observations at Sea

Searchingtook place in Balsfjord,Tromse, Northern Norwayfrom a small researchvessel the FF Hyas,Norges Fiskerihegskole,Tromse, length 12m!. Balsfjordis a subarcticfjord 90 km~!with a 30 m sillat its entrance,with depthsin the innerfjord droppingto 190m. Trawlingsurveys have shown a preponderanceof cod Gadusrnoruaa, but alsosignificant catches of haddock.There is a small localfishery for cod and haddockin the spring,and reports from fishermensuggested that haddock spawned at the head of the fjord.

Sampling took place when individual fish echoes were detected on or close to the seabed on the echo-sounder.The ship was stopped, anchored by the bow,and the hydrophonehung 2 m abovea weight on the seabedby a cordattached to a smallsubmerged buoy, Sound recordings were made for a minimumof 15 minutesat eachstation with the mainengine and auxiliarygenerator of the ship shut down.The positionof the shipwas determined by GPS.

Four surveyswere carried out at Balsfjord7-19 April 2000;10-12 May 2000;9-10 December2000; 3-7April 2001!,The distinctive sounds of haddockwere detected at soinetime duringeach of the 4 surveys,though not at all stationsand with varyingincidence. In the first survey,12stations were examined.Distinctive haddock sounds were recorded at the majorityof stationswithin the main basin,especially close to the headof the fjord. Slowlyrepeated knocks, made up of doublepulses, were the most common Figure 3!. Somewere short a few seconds!,others extended over several minutes,Occasionally, sounds with a fasterrepetition rate were recorded, suggesting that the haddockwere engaging in agonisticand courtshipactivities. At one stationin the mainpart of the fjord, repeated grunts were recorded which lackedthe double pulse structure characteristicof haddock. Thesewere tentatively identified as coming from cod.

Soundswere recorded at all timesof the day andnight. However,in two areasa continuouslow frequency rumbling was detected at night, within which individual haddock knockscould be detected.

Duringthe secondsurvey, sounds were recorded at four of the five stationssurveyed, All stationsat the headof thefjord yielded haddock sounds, and at threeof them,the lowfrequency rumbling soundwas audible at night. At one stationit provedpossible to recordfor 10 minuteperiods every hour overa 24hour period.This revealed a 10dB increasein ambientnoise level at night,which wasattributable to the simultaneousproduction of soundby manyhaddock.

Thethird surveywas carried out at the beginningof winter,At threestations long slow knocking soundswere detected, made up of doubleand occasionallytriple pulses,confirming the presenceof haddock,The sounds were rare, however, and no low frequency rumbling was detected, suggesting that spawninghad not yet begun.'The fourth surveyinvestigated 22 stationsat the headof Balsfjord during Spring. Many haddock soundswere detected at stations closeto the head of the fjord. Lowfrequency rumbling wasdetected at nightat threestations. No haddocksounds were detectedat stationsalong the easternedge of the fjord.

Proceedingsfrom the internationai Workshopon the Appiications of PassiveAcoustics to Fisheries 51 Discussion Bylistening, it provedpossible to locateconcentrations of spawninghaddock at the headof Balsfjordduring Springover two successiveyears, confirming that passiveacoustics provide a reliable non-invasive technique for identifying the preciseareas where haddock spawn. The method maygreatly assist in the searchfor the spawningareas of commerciallyimportant food fishes. Sound production was most intense at night.

Acknowledgments Thesestudies were collaborative and depended on the efforts of others. Researchat the FRSMarine Laboratory was conducted with Licia Casaretto,Marta Picciuilin,& MarkWood, all of the Universityof Aberdeen. Studies at sea involved Licia Casaretto,Marta Picciullinand also Kjell Olsen and Captain Eilert Halsnes from the University of Tromso.

References Ames,E.P. 998! Cod and haddock spawning grounds in the Gulf of Maine, In;The implications of iocalized fishery stocks eds.von Herbing, I.H.,Tupper, M., & Wilson,J,! 55-64.NRAES, Ithaca, New York.

Boudreau,PR. 992! Acoustic observations of patterns of aggregation in haddock Melanogrammus aeglefinus!and their significance to production and catch. Can.J.Fish. Aquat. Sci.49,23-31.

Hawkins,A.D, &. Amorim, M.C.P.000! Spawning sounds of the male haddock,Melanogrammus aegiefinus. Env.Biol. Fish. 59,29-41.

Hawkins,A.D. and Chapman,C J.966! Underwater sounds of the haddock Melanogrammusaeglefi- nus L!. J. mar. biol. Ass. U.K.46, 241-247,

Hawkins,A,D. and Rasrnussen,KJ. 978! The calls of gadoid fish. J.mar. biol. Ass.U.K.58, 981-911,

Solemdal,P., Knutsen, T., Bjerke, H., Fossum, P., & Mukhina,N. 997! Maturation, spawning and egg drift of Arcto-Norwegian haddock Melanogrammus aeglefinus!, J.Fish. Biol,,51 Suppl.A!, p 419.

Waiwood, K.G.& Buzeta,M.I. 989! Reproductive biology of SouthwestScotian Shelf haddock Melanogrammus aeglefinus!.Can.J. Fish. Aquat. Sci.46, 153-170.

Proceedings from the international Workshop on the Applications of Passive Acoustics to Fisheries 52 I/lustrationsand Diagrams

0 1 2 S 4 5 6 7 8 9 s

1 kHz

100 200 300 400 500 ms

Figure 1. Repetitiveknocks from a malehaddock during solitary display.

0 2P 4Q 60 60 ms 0 20 40 60 60 ms 0 20 40 60 80

Figure2. Waveformsof'knocks' from threeindi vidual males A,B &C!.

0 1 2 3 5 6 7 6 9 s

100 200 300 400

Figure3. Soundsrecorded from Balsfjord,identified as haddock.

Proceedingsfrom the International Workshop on the Applications of PassiveAcoustics to Fisheries 53 ~ ~Usinga TowedArray to Survey Red Drum Spawning Sitesin the Gulf of INexico

Scott A Molt

Universityof Texasat Austin Marine ScienceInstitute, 750 Channel View Drive,Port AransasTX 78373 USA, sholt@utrnsi,utexas.edu

introduction

The red drum Sciaenopsocellatus! is an important recreational and, in some locations,commercial speciesthroughout its range.Juveniles generally live in estuariesand move to nearshoreoceanic watersas they reachmaturity Pearson1929!. Adults range widely overthe nearshorecontinental shelf waters throughout the year but apparently move to coastal waters to spawn Overstreet 1983!, Spawningis generally thought to take place in coastal waters near inlets Jannke 1971,Holt et a/. 1985!although Lyczkowski-Shultzet al, 9SS! found eggs and larvaeout to 34 km from shore in the easternGulf of Mexico.There is alsoevidence of limited spawningactivity within estuaries in Florida Murphy and Taylor 1990,Johnson and Funicelli 1991! and in North Carolina Luczkovich et a/.1999!.

Thelocation of spawningareas has typically been inferred through captureof fishwith mature gonadsor the distributionof eggsand larvae.Red drum makeloud, characteristic sounds during spawning Guest and Lasswell1978!. Listening for the characteristicsound production has recently beenused to locatered drum spawningsites in IndianRiver Lagoon, Florida Johnsonand Funicelli 1991!,and in PlamicoSound, North Carolina Luczkovich et a/.1999!,and at tidal inlets in South Carolina Collins et althese proceedings!.These surveys have been done with both hand-held hydrophonesand remotely placed sonobuoys.

Overa four-yearperiod from 1998-2001,a hydrophonemounted on a pierin the AransasPass, Texas tidal inlet hasbeen use to recordsounds of red drum spawningactivity every evening during the Septemberthrough October spawning period. Recordings were madefor 20 s every15 m from 1700to 0100hours and spannedthe 4-5 hourevening spawning period of reddrum Holt et al. 1985!.Red drum produced characteristic spawning sounds from about one hour before sunset to aboutthree hours after sunsetwith the mostintense activity occurring during the two hoursfollow- ing sunset S.Holt, unpublished data!. These data, aiong with collectionsof reddrum eggs and lar- vaeat the site,confirmed that red drum spawnactively in the vicinityof the tidal inlet.The spatial extentof red drum spawningwas still unknownbut it wasclear that surveyingsound production duringspawning was an effectivemeans of locatingspawning sites.

Thispaper reports on a surveyof potentialspawning sites in the nearshorewestern Gulf of Mexico using a towed hydrophone array.

Proceedingsfrom the /nternationalWorkshop on the App/icationsof PassiveAcoustics to Fisheries 54 Study Area and Methods Thesurvey was conducted in the northwesternGulf of Mexicoalong the centralportion of the Texas,USA, coast, Preliminary surveys with a hand-heldhydrophone in the arearevealed that red drum spawningsounds were more commonly observed along the 10 rn contourthan in eithershal- low waternear the surfzone or fartheroffshore in deeperwater. Mence, for this initial survey,three transectswere established roughly parallel to the coastlinealong the 10 m contour.Transects were sampledon threeconsecutive nights onetransect per night! in late September2000. Sampling commencedabout 30 -45 min before sunset,which was about 1925,and ran for about 3.5 hours.

The tawed arraywas composed of eight hydrophones in an 80 meter cable connected to a 200 metertowing cable and was towed at approximately4.5 kts from a 105foot sterntrawler. The array isspectrally flat i.e.no peaksin sensitivity!from 6Hz to 18kHz, with a sensitivityof approxirnately- 191dB re 1 voltper pPaat 7.2kHz. The signals from eachof the eight separatehydrophones were savedto an eight-trackdigital recorder TascamDA-88! sampling at 44 kMz.The combination of a temporalwindow of spawningvocalizations about 3.5 hours! and optimumtowing speedfor the array of ,5 kts! limited each nightly transect to about 20 km.

Reddrum producelow frequencysounds described as knocks Fishand Mowbray1970! or drumming Guestand Lasswell 1978!. Although Guest and I asswell918! foundthe "dominant energy" of theirrecordings from a tankwas around 240 Hz - 1000Hz, I havefound the fundamental frequency of reddrum calls obtained from unconstrainedfish in the field to consistentlybe around140 Hz 160Hz Fig,1!. Each call consists of a variablenumber of pulses,or knocks,that arerepeated at a rangeof pulserepetition rates Guest and Lasswell 1978, laboratory observations; S Holt unpublisheddata, field observations!,Whether there arespecific behaviors associated with specificcall typesis unknownbut the existenceof numerousvariants in call patternsuggests individual variability.Despite variation in callduration and pulserepetition rate, the consistencyin fundamentalfre- quencyand general character of the callpattern make recognition by ear relatively easy.

Recordedsignals from the arraywere analyzed by listeningto the tapeswhile observing the realtime powerspectra and real-timesonogram on a computerscreen SpectraPro3.32, Sound Technologylnc.!. Two classes of reddrum sounds could be distinguished. One was a lowfrequency rumblewith a prominentenergy peak in the 150Hz range, This was presumed to befrom large numbersof reddrum producing sounds simultaneously but at somedistance from the hydrophone, The sound produced by the ship and the hydrophone itself was determined to have dominant energyin the rangeof 250Hz - 300Hz.! 'The other classof soundswas clearly distinguishable calls made by an individual or small group of red drum.

Theoccurrence of backgroundrumble indicates spawning activity in thevicinity of thehydrophone but morework is neededbefore the spatialscale over which those sounds travel can be meaning- fullyinterpreted. For this paper, I willdescribe only the distribution of individualor small-groupcalls. Fromour observations and the work of Luczkovichetal. 999!, it appearsthat the drumming of an individualred drum can be distinguished over a distanceof about100 rn. Thus, we can roughly definethe spatialdistribution of individualred drumdetected by the hydrophonesas a 200rn

Proceedingsfrom the internationaliVarkshop an theApplications of PassiveAcoustics to Fisheries 55 swathalong the transect, The physical location of eachobservation was determined by comparing the underwaydata recorded from the ship's SAIL system which included time and latitude/longitude aswell asseveral physical parameters! and the clocktime on the digital recorderwhich was carefullysynchronized with the shipsclock. The data set was initially constructed by recording the hour/minute/secondof eachidentifiable call. The data wasthen summarizedby countingthe nurn- ber of callsheard in eachone-minute segment the shipslocation was recorded once per minuteso that wasour finestscale of spatialresolution!. The numberof calls/minutewas arbitrarily divided in two groups;<16 per minuteand 16or moreper minute,This division was set to separatethe typi- callylower occurrence of drumming-10 perminute was typical! from the relativelyrarer higher rate we rarelyheard more than 20-30per minute!.Finally the drummingrate i.e.none, low, or high! was plotted on the cruise track.

Results Reddrum calls were detected along mostsections of the threetransects Figs. 2 &3!.Calls were detectedboth in extensiveclusters and in isolatedoccurrences along the transects.For example, on the SanJose "A" transect Fig. 3!, there are two occurrencesof nearcontinuous calling that extend over several kilometers. On the same transect, there are several isolated occurrences of red drum callsand extensive segments up to 4 km!where there are no calls.Transect segments were dominated by the absence of red drum calls. There was a total of 474 minutes of observations over all transects.Of those,330 minutes 0%! had no red drum calls,109 minutes 396! had low drumming rates <16per minute!,and 35 minutes0/0! had high drummingrates >15 per minute!.Highdrurn- ming activitywas concentrated in two segmentsalong the SanJose "A" transect and in one segment of the Matagordatransect. One segment, on the eastend of the transect,spanned 5 minutesof towing time andcovered 600 m. The other, farther to the weston that transect,spanned 14 minutesof towing time and covered2.2 km. Only 4 of the 14 minutesin this segmentwere low leveldrumming and none were without drumming.

Themost intense drumming activity occurred between 1830 and 2130. Little drummingwas heard after 2130on the Matagordaor SanJose "A" transects datafor the laterpart of the SanJose "B" tran- sectwas lost due to an audiotape malfunction!.Low and high drummingrates were distributed throughout this time period without any temporal pattern.

Discussion Basedon the distributionof soundproduction, red drum appearto spawnall alongthe nearshore regionof the centralTexas coast, This survey was not spatiallycomprehensive enough to fully delin- eatethe spawningarea, but it is clearfrom this initial surveythat spawningactivity is widespread, Spawningwas not concentratedat inletsas suggested by earlierauthors Simmonsand Breuer 962!,Jannke971!. Areasof the coastlinefar removedfrom the inletshad relativelyintense drumming activityand confirms suggestions of Murphyand Taylor 990! that spawningalso occurs over the nearshore continental shelf.

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 56 It is still not exactlyclear how drumming by malered drum shouldbe interpreted.There are at least threepossibilities: 1!the drumming male will engagein spawningat that locationon thatevening; 2! the drummingmale is caliingfrom a potentialspawning site but will spawnat that site on that dayonly if joined or selected!by a cooperativefemale; or 3! the drummingmale may move to another place before engaging in spawning.Luczkovich et al. 999! observed instancesof red drum drurnrningwithout finding eggs and Johnson and Funicelli 991! foundred drum eggs without hearing drumming. In both instances,short-term observations were made in shallow water with a handheld hydrophone and the observers may have disturbed the fish or missedpart of thespawning process.At this point,it is assumedthat drurnrningroughly equates to spawningbut the issue needs more investigation.

Thedistribution of drummingmale red drum suggest that some,if notmost, of the spawningtakes placeamong widely distributed individuals as opposed to highlyaggregated groups. Only 7/0 of the one-minutesummaries recorded high drummingrates of morethan 'I5 callsper minute.Guest and Lasswell978! reporteda callrate of about 2-16calls per minutefor captivered drum in courtship.Our subjective impression from listeningto the tapeswas that manyof the low drurn- mingrates were produced by a singlefish. There were, however, at leasttwo largeaggregations of drummingfish. Both were in the vicinityof CedarBayou, a relativelysmall but historicallypersistent tidal inlet. One of these aggregationsspanned a linear distance of over 2 km and its breath was undetermined.The number of calls per minute up to 40! indicatesthat several red drum were calling simultaneouslywithin the roughly100 meter detection range of the hydrophonesand this"density" was consistent over most of the 2 km stretch.

Thefull extentof the offshorespawning area of red drum is yet to be determinedand much remainsto be learnedabout their reproductive strategies, but the useof towedhydrophone arrays offers promise of an efficient meansto achievethose goals,

Acknowledgments I thankJohn Keller for processingthe audio data and Cameron Pratt for preparingthe figures. The crewof the RN Longhornwas instrumental in acquiringthe recordings,This work wasfunded through a grant from the Sid W.Richardson Foundation.

References

Fish,M. P.,and W.H.Mowbray. 1970. Sounds of western North Atlantic fishes;a referencefile of biological underwater sounds.Johns Hopkins Press,Baltimore,

Guest W Cand J. L Lasswell.1978A note on courtship behavior and sound production of red drum. Copeia 1978: 337-338.

Holt,G.J., S. A, Holt, and C.R. Arnold.1985. Diel periodicity of spawningin sciaenids.Marine Ecology Progress Series 27: 1-7.

Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 57 Jannke,T.E.1971, Abundance of youngsciaenid fishes in EvergladesNational Park, Florida, in relation to seasonand other variables.University of MiamiSea Grant Technical Bulletin 11: 128p,

Johnson,D.R., and N.A.Funicelli. 1991. Spawning of the red drum in MosquitoLagoon, East-Central Florida. Estuaries 14: 74-79.

Luczkovich,J.J., H.J. Daniel, III, and M, W, Sprague. '!999. Characterization of critical spawning habitats of weakfish,spotted seatrout and red drum in PamlicoSound using hydrophone surveys. Pages 128, NorthCarolina Department of Environmentand NaturalResources, Morehead City, NC.

Lyczkowski-Shultz,J J,P. Steen, Jr., and B.H. Comyns, 1988. Early life historyof reddrum Sciaenops ocellatus!in the northcentralGulf of Mexico.Pages 148, Mississippi-Alabama Sea Grant Consortium.

Murphy,M.D., and R.G.Tayior. 1990, Reproduction, growth, and mortality of reddrum Sciaenopsocel- latus in Floridawaters. FisheryBulletin, US 88: 531-542.

Overstreet,R,M. 1983. Aspects of the biologyof thered drum, Sciaenops ocellatus, in Mississippi.Gulf Research Reports Supplement 1:45-68.

Simmons,E.G., and J, P. Breuer. 1962. A studyof redfish,Sciaenops ocellata Linnaeus and blackdrum, Pogonias cromis Linnaeus, Publications of the institute of Marine Science 8: 184-211,

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 58 Figure t, Sonogramof a reddrum call from an unconstrainedindividuaiinthe field.This particular cail consistsof threewidely spaced knocks foliowed by two pairs of closelyspaced knocks.

Figure2. LocationSan Jose "A"and "8" hydrophonetransects. The lineindicates the cruisetrack. Bars above the line indicatelow one-minute drumming rates at thatlocation. Bars below the line indicate high one-minute drumming rates.Sampling time is indicated randomly along the track.

Figure3, l ocationof the Matagorda hydrophonetransect. See Fig.2 legend for details,

Proceedingsfrom the lnternationai W!rkshop on the Apph'cationsof PassiveAcoustfcs to Fisheries 59 ~ ~ ~ ~ Reef FishCourtship and Mating Sounds:unique signals for acousticmonitoring

Phillip S. Lobel

Boston University Marine Program,Marine BiologicalLaboratory Woods Hole, MA 02543

The following text is extracted from: Lobel, P.S.2002 Diversity of fish spawning sounds and the application of passiveacoustic monitoring. Bioacoustics 12:286-289.

The table is reprinted from: Lobel, PS.001! Acousticbehavior of cichlid fishes.J.Aquaculture & Aquatic Sci.9, 167-186.

Introduction Marinebioacoustics is a rnultidisciplinaryfield with practicalapplications to economicallyimportant globalfisheries issues. One application of bioacousticsuses passive acoustic technology to record temporaland spatialpatterns of fish reproductionby detectingsounds associated with spawning Mann and Lobel 1995!.The applicability of this tool depends upon whether specific species pro- ducereliably identifiable sounds during courtship and spawning Label 2001a!. Monitoring courtshipand spawningsounds can be usedto defineimportant breeding habitats a priority in planning marine protected areas!and to understand the relationshipsbetween fish reproduction and the fate of larvae in oceancurrents. Mating is the crucial biological event to monitor in order to understandthe life historytactics of fishes,espeoally coastal marine species with a pelagiclarval phase.Mating is alsoa criticalendpoint measurement in pollutionimpact studies. Measuring a decreasein reproductionmay be an earlyindication of subtleadverse affects of pollution.It is well knownthat manyfishes produce sounds associated with courtship,However, which fishes produce specific sounds during spawning is not as well known.

A strong casefor the value of bioacoustic monitoring is made by the discoveriesthat two of the world'smost valuable fishes, cod and haddock,produce distinct courtship and spawningsounds Nordeideand KjellsbyI 999,Hawkins and Amorim2000!. This paper documents the spawning sounds of four coral reef fishesand illustrates different types of acoustic patterns.

Proceedingsfrom the Internationai IrVorkshopon the Appiications of PassiveAcoustics to Fisheries 60 Examplesof Spawning Sounds Methods are reported by Lobel 001 a! and spawning behaviorswith sounds are described in references cited below for each species,

Ostracionmeleagris Family Ostraciidae!produces a cleartonal sound with one harmonic Figure 1a, Lobel 1996!.

Dascy//usalbisella Family Pomacentridae!produces a spawningsound composed of a simple series of one to four pulses Figure 1b!.This spawning sound differs from its courtship sound only by having fewer pulses Lobel and Mann 1995!.A spawning sound was not found in another pomacentrid Abudefdufsordidus! or in related freshwater cichlids Lobel 1998,2001b, Lobel and Kerr 1999!, even though these other fishes produce courtship sounds similar to D.albisella.

Hypoplectrusnigricans FamilySerranidae! produces a distinct two-part spawning sound Figure 1c!. A short downward frequency sweepis followed by a short silenceand then followed by a broad- band sound,which is made asthe fish disperse gametes Lobel 1992!. This sound may be a combination of swimbladder sound and hydrodynamic noisefrom rapid fin fluttering.

Scarusiserti Family Scaridae!spawns in aggregations of about 20 to 40 individuals.These fish gather in groups over the reef surfaceand then suddenly and with great speed,rush upwards a few meters, turn rapidly while releasinggarnetes and dart back to the reef shelter Lobel 1992!. This spawning soundis hydrodynamicnoise produced by the fish'sswimming movements Figure 1d!.

Discussion Why do some fishes make spawning sounds?By the time mating has started, mate selection has already taken place.Such sounds may have originated as a mere by-product of movements associated with swimming and gamete extrusion. Furthermore,these sounds are in the low frequency range that has been shown to be highly attractive to predators,e.g. sharks Myrberg et al. 1972!. Spawning fishes may be lessresponsive to predatory threats once they are completely preoccupied with mating Lobeland Neudecker1985, Sancho et al.2000!. The possibility that spawningsounds may be an attracting signal to predatorson adults or newly spawnedembryos is a signiFicant potential cost in terms of natural selection.This implies that spawning sounds must also provide some evolutionary advantage as well. Spawning sounds may haveevolved to behaviorally synchro- nize gamete release in order to maximize external fertilization.

Proceedingsfrom the International VYorkshopon the Applications of PassiveAcoustics to Fisheries 61 Table1. Possibleinformation transmitted by sound patterns in orderof increasingcomplexity of signal interpretation!:

Message Acoustic clue

Mate location sound occurrence

Readiness to spawn sound occurrence synchonizationof gameterelease = matingor spawningsound!

Vigor l aggressiveness duration of call &I call repetition rate

individual size dominant frequency

Speciesidentity variation in pulse repetition rate in a call, number of pulses in a call,variation in pulseamplitude, call duration, plus color patterns & behavior

Individual identity combination of all above clues,plus other features of behavior

reprinted from Label 2001b!

Acknowledgement Researchfunded by the ArmyResearch Office DAAG-55-98-1-0304 andDAAD19-02-1-0218!. My participation in this meeting was supported by the Woods Hole SeaGrant office.

References Hawkins,A. D. & Arnorim,M.C. P. 000! Spawningsounds of the malehaddock, Melanogrammus aegelfinus. Environ. Biol. Fishes 59, 29-41.

Lobel,P, S992! Soundsproduced by spawningfish. Environ. Biol. Fishes 33,351-358,

Lobel,P.S. 996! Spawningsound of the trunkfish,Ostracion meleagris Ostraciidae!. Biol. Bul, 191, 308-309

Lobel,P.S. 998! Possiblespecies specific courtship sounds by two sympatriccichlid fishes in Lake Malawi, Africa. Environ. Biol. Fishes 52, 443-452. LobelP.S. 001a! Fishbioacoustics and behavior: passive acoustic detection and the application of a closed-circuitrebreather for field study, Marine Technology Society Journal 359-28

Lobel,P.S.2002 Diversity of fish spawningsounds and the applicationof passiveacoustic monitoring. Bioacoustics 12:286-289.

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 62 Lobel, PS.001b! Acoustic behavior of cichlid fishes.J.Aquaculture & Aquatic Sci.9, 167-186,

Lobel, P.S.2002Diversity of fish spawning sounds and the application of passiveacoustic monitoring. Bioacoustics 12:286-289.

Lobel, P.S. & Kerr,L M. 999! Courtship sounds of the PacificDamselfish, Abudefdu sordidus Pomacentridae!. Biol. Bul. 197, 242-244.

LobelP.S. & Mann,D. A. 995! Spawningsounds of the damselfish,Dascyllus albiseila Pornacentridae!,and relationship to male size.Bioacoustics 6, 187-198.

Label,P.S. & Neudecker,S, 985! Diurnalperiodicity of spawningactivity by the hamletfish, Hypoplectrusguttavarius Serranidae!, In; The Ecology of CoralReefs, Vol. 3, Symposia Series for UnderseaResearch, M. L. Reaka, ed!, NOAA, Rockville, MD, pp.71-86

Myrberg,A, AHa S.J.,Walewski S. & BranburyJ. C, 1972. Effectiveness of acousticsignals in attracting epipelagic sharksto an underwater source.Bull. Marine Sci.22, 926-944.Sci. 56, 326-332,

Nordeide,J.T. & Kjellsby,E. 999! Soundfrom spawningcod at their spawninggrounds. ICES J. Mar. Sci56, 326-332.

Sancho,G., Petersen, C.W. 8 Lobel,P.S. 000! Predator-preyrelations at a spawningaggregation site of coral reef fishes.Mar. Eco. Prog. Ser.,203,275-288.

Proceedingsfrom the international IVorkshopon the Applications of PassiveAcoustics to Fisheries 63 Figure!.Sonograrns produced using the hainming window function and an FFT size of 2048 points Canary software!,Frequency scale is thesame in all graphs,but timescale differsin each. a! Ostracionmeleagris, duration 6213 ms,dominant frequency DE258 Hz b! Dascyllusalbisei!a,3 pulses duration l30 ms DF 328 Hz c! Hypopiectrusnigri- cansduration 1587 ms; DF 656 Hz, d! Scar us iser ti duration329 ms, DF twopeaks! 492 0 2l l HzSize range of these fishesisabout 10-20crn Sl. reprintedfrom Lobel 2002!.

Proceedingsfrom the lrrternationa/ Workshop on the App ication»of PassiveAcoustics to Fisheries 64 ~Using ~ Passive ~ ~Acoustics to Nlonitor ~ ~Spawning of Fishes ~ ~in the DrumFamily Sciaenidae!

JosephJ. Luczkovich" and Mark W Sprague'

'Institutefor Coastaland MarineResources, 'Department of Biology,'Department of Physics, EastCarolina University,Greenville, NC, USA 27858 A [email protected] spraguernOrnail.ecu.edu

Introduction Drumfish FamilySciaenidae! are known for their sound production during mating, from which the familyderives its name Fish and Mowbray 1970!, Members of thedrum family are dominant speciesin the large and valuable commercial and recreational fisheriesin North Carolinaand the SoutheasternUSA. Recently, concerns have been raised about the deciine in the populationand spawningstock of somesciaenids, especially the red drum,5ciaenopsoce/latus Ross et al.1995!. Onemanagement option that has been suggested is to createspawning reserves, but spawning areasmust be surveyedfirst in orderto protectthem. Sciaenid fishes held in captivityproduce species-specificsounds associated with spawningbehavior Guest 8 Laswell1978; Connaughton andTaylor 1996, Sprague et al,2000!and recentlyspawned eggs and sounds co-occur in field samples Mokand Gilmore1983, Luczkovich et al. 1999!.Spectral analysis of thesesounds allows us to identifyeach sciaenid species based on their soundproduction, even when they co-occurin the samearea seeSprague et al 2000,Sprague and Luczkovichthese proceedings!. Because sounds are producedby malefishes in theSciaenidae in communication during courtship and spawning, we areable to usethese sounds as an indicatorof spawningareas. Here we reporton howwe used passiveacoustic survey techniques for mappingspawning areas of reddrum, weakfish Cynoscion regalis!,spotted seatrout C.nebulosus! and silverperch Bairdiellachrysoura! in ParnlicoSound, NC.

Methods Soundsof sciaenidfishes were recorded in two ways:1! a hydrophoneand recording system deployedfrom a smallboat that was able to movefrom station to station;and 2! a hydrophone arraysystem on a remotelyoperated vehicle ROV!with low-lightvideo capabilities. From May through September during 1997 and 1998,we used an lnterOcean 902! CalibratedAcoustic ListeningSystem [consisting of a gain-adjustablepre-amp, a hydrophone,and an overallsound pressurelevel meter] and a Sony TCD-D8! Digital Audio Tape recorder to recordfrom a smallboat at fixedstations in ParnlicoSound for upto 5 minper station after sunset on monthlyintervals. The

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 65 hydrophonewas suspended over the side of the boat at a depth of 1 rn. In order to confirm that the siteswhere we recorded sounds were spawning areas, we conducted ichthyoplankton surveys at thehydrophone stations immediately after each sound recording ended. A 28-cmdiameter bongo netwith 500pm mesh was towed at the surfacefor 5 minto capturethe buoyanteggs. In Mayof 2001,we useda PhantomS2 ROV with low-lightvideo and a calibratedInternational Transducer Corporation ITC-4066! hydrophone array to recordthe soundproduction of a silverperch in situ, Thehydrophone array was mounted on the ROVon a 1.5m longboom. The pre-amplified signal fromthe hydrophonearray was sent up the 900-footROV umbilical cord to an audioand video recorderon boardthe boat, Althoughwe used a four-hydrophonearray, which was originally intendedto help localizefish sounds,only one hydrophone hydrophone number 4 locatedon the far right sideof the boomas viewed from the point of view of the videocamera! was selected for recordingin thisstudy. All soundrecordings were resampled at 24 kHzfrom the original tapes usinga NationallnstrumentsA/0 board,We used 1024-point Fast-Fourier-Transforms FFTs! to obtainspectrograms and estimates of overallsound pressure levels. To generate the spectrograms, we usedVirtual instruments written for usewith LabViewdata acquisitionsoftware and Mathematicafor creatingplots. Statistical analysis was done using Systat 10 Spragueet al.2000!.

Results Wedetected the spawningaggregations of silverperch, weakfish, spotted seatrout, and red drum in PamlicoSound during both 1997and 1998.Male silver perch were detected on boththe eastern andwestern side of ParnlicoSound, but wereloudest at the inletstations during May and June of bothyears Figure 1a!.The male weakfish were detected making their characteristic "purring" soundsonly at stations on the eastern side of PamlicoSound, near Ocracokeand HatterasInlets in Maythrough August of bothyears, but the peakcalling was in Mayand June Figure 1b!. Spotted seatroutwere found producing their grunts at stations on both sides of the sound from June throughSeptember, but were moreregularly recorded near the BayRiver on the westernside of PamficoSound in Julyofboth years Figure1c!. Reddrum were heardboth at the inletsand on the westernside of the soundin Augustthrough Septemberboth years,but they wereloudest in Septembernear the mouthof the BayRiver in the westernside of the sound Figure 1d!. The overall pictureis one of a seasonallyshifting use of specificareas near river mouths and inlets by the four species,with distinct peak spawning times for each species.To demonstrate that these sounds are associatedwith spawningactivity, we collectedsciaenid type eggsin the areaswhere we had recordedfish sounds. The overall sound pressure level in dBre 1 pPa!at eachstation was directly correlatedwith the log]ptransformed sciaenid type egg density Figure 2, r =0.61!. This suggests thatthe sounds produced by malefish! and the recentlyspawned sciaenid eggs produced by femalefish! are associatedin spaceand time, an indication that the sounds are associatedwith spawning.

Thelow-light capabilities of the videocamera of the Phantom52 ROV allowed us to seefish as they madetheir sounds. Thus, we were able to measurethe sound production by silverperch when they werea knowndistance from the hydrophone,In this way,we wereable to determinethe sound

Proceedingsfrom the International Workshopon the Applications oFPassive Acoustics to Fisheries 66 sourcelevel for an individualfish in situ,which is a necessaryfirst stepfor modelingsound production andpropagation. In May2001, we hadthe opportunityto capturea singlesilver perch on video while it passedin front of the ROVand the hydrophone,producing some of the loudestsounds that we hadrecorded during our surveys,The ROVwas deployed in WallaceChannel, near Ocracoke Inlet,at a depthof 28 feet,in an areawhere we hadpreviously recorded loud vocalizationsof both silverperch and weakfish. Poor water clarityand strong currents at this site limitedthe camera's abilityto seeand the mobility of the ROV,which was deployed with a down-weightrig to holdnear to thebottom during the tidal current shifts, On May 5,2001 at 21:18;05,we iecorded a callingmale silverperch and measured the sound pressure level at hydrophone¹4 whenthe fish was swimming through from left to right!the viewing field of the low-lightvideo Figure3!. At thispoint, the soundpressure level was 126 dB re 1!iPa.At 21:18:15,after the fish swamacross the videofield of view,and closer to hydrophone¹ 4, which was on the boomto the right,the sound pressure level wasmeasured at 129dB re [email protected], the overallsound pressure level increased as the fish sound source!got closer to the hydrophone.

Discussion

The passiveacoustic approach we have described is limited to soniferous fishes,but almost all sci- aenidsfall into this category. Soniferous sciaenid Fishes produced sounds during spawning in ParnlicoSound, and these general areas have been mapped. Weakfish and silver perch call com- rnonlynear Hatteras and Ocracoke inlets, peaking in Mayand June, whereas spotted seatrout were commonlydetected calling throughout the summerin both easternand westernParnlico Sound, peakingin July.Red drum were less commonly detected by passiveacoustics than the other speciesof sciaenids,perhaps due to theirdeclining spawning stocks, they were only detected at the inletsand in westernParnlico Sound in Augustand September, with thegreatest sound production at the mouthof the BayRiver in September.Sciaenid-type egg abundancewas correlated to overall soundpressure level loudness!of sciaeniddrumming in fieldsurveys, suggesting that egg pro- ductioncould be estimated from sound production. This passive acoustic approach to estimating spawningstock relative abundance would be useful to fisherybiologists attempting to verifythe variationsin spawning stock sizesfrom year to year, No estimates of absolute fish abundancecan be madeat the presenttime; but biomassestimation may be possiblein the future if active acoustics were also used.

Fromthe ROVhydrophone measurement of sound source levels,we can now estimate the distance overwhich fish sounds can be detected. For an individual silver perch calling 1 mfrom the hydrophoneat 129dB re 1 pPa, assuming a cylindricalspreading model, where rmax is the radius of thecylinder, see Luczkovich et al. 1999!, we can now estimate r~,= 10"~""'"'~~~"""'v" = 79m. However,this cylindrical spreading model assumes that soundwaves will propagatethrough water withconstant temperature and salinity and a uniformdepth, conditions that are unlikely to occurat the inlets,Consequently, we maybe over-estimatingthe distancewhich we candetect sounds. It is alsopossible that sound may be channeled further than this due to particularbathymetric and water stratification conditions peculiar to Pamlico Sound and the inlets.

Proceedingsfrom the InternationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 67 References Connaughton,IVI.A. and M, H, Taylor. 1996. Drumming, courtship, and spawningbehavior in captive weakfish,Cynoscion regalis. Copeia 1996,195-199

Fish,M, P,and W. H. Mowbray. 1970. Sounds of WesternNorth AtlanticFishes, The Johns Hopkins Press,Baltimore and London, 194 pp.

Guest,W. C. and J. E, Lasswell. 1978. A noteon courtshipbehavior and soundproduction of reddrum. Copeia 1978, 337-338,

Luczkovich,J.J., M WSprague, 5, E. Johnson, and R.C.Pullinger 1999. Delimiting spawning areas of weakfish,Cynoscion regalis Family Sciaenidae! in Parnlico Sound, North Carolina using passive hydroacousticsurveys. Bioacoustics 10, 143-160.

Luczkovich,J.J., H, J, Daniel III, M. Hutchinson, T, Jenkins, S. E. Johnson, R.C. Pullinger, and M.W. Sprague.2000. Sounds of sexand death in the sea:bottlenose dolphin whistles silence mating choruses of silver perch. Bioacoustics 11, 323-334.

Mok,H. K. and R.G.Gilmore, 1983. Analysis of sound productionin estuarineaggregations of Pogoniascromis, Bairdiella chrysoura, and Cynoscionnebulosus Sciaenidae!.Bulletin of the Institute of Zoology,Academia Sinica. 22, 157-186.

Sprague,M WJJ. Luczkovich,R.C. Pullinger S. E. Johnson, T Jenkins,and H.J. Daniel III. 2000. Using spectralanalysis to identifydrumming sounds of someNorth Carolina fishes in the family Sciaenidae.Journal of the ElishaMitchell Society 116,124-145.

Ross,J, L., Stevens, T.M. and Vaughan, D, S. 1995. Age, growth, reproductive biology, and population dynamics of red drum Sciaenopsocellatus! in North Carolinawaters. Transactions of the American FisheriesSociety 124,37-54.

Proceedingsfrom the International IVorkshopon the Applications of Passive Acoustics to Fisheri es 68 I a!

! !&we ~:i!i!'8 ~!. ,i!,, !!

T ? " i ~ T' Figure2 l.og 10transformed sciaenid-type i egg production plotted versussound pressure level fdb re t @pa}.Line fitted wi th a ocaDy weigh ted regression LOPYESS!.

s y j 4+ I g ,! ! O ~!!,' !! 4 ? !!!!~ j 0~ >- +~~~ Q.' '~Vi~ '??0 ?2o ?30 ?40 1 SovndPress&"e L@~!!? a[3;

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Figure3. Spectrogram of 24 s segmentof theROY audio track from hydrophoneA, recordedS May200 l, beginning at 2l: 18:00.The sound source levels in soundpressure in d8 re F@pa! are shown for two times at which the silver perchfirst appearsin the ROIrvideocamera field of view at 5-6 s! andjust afterit passedout of view of the camera, when it was the loudest' at 16-17s!

Proceedingsfrom the international 5'orkshop on the Applications of PassiveAcoustics to Fisheries 69-- Is acousticcalls a prematingreproductive barrier between two northeast Atlanticcod Gadusmorhua! groups a review

Jarle Tryti Nordeide' and Jens Loss Finstad'

'Facultyof Fisheriesand Natural Sciences, Bode Regional University, N-8049 Bode, Norway. 'Masterstudent at: Departmentof Fisheriesand MarineBiology, University of Bergen,Norway

Surnrnary Thispaper reviews the first attemptsto testthe hypothesisthat spawningcalls of malemigratory "Arctic"and a stationary"Coastal" cod group, which are sympatric during the spawningseason, is a premating behavioural reproductive barrier.As predicted from the hypothesis,a hushed hubbub of soundwith a transientcharacter, band-width and harmonicspacing typical of cod calls,was revealedat a majorspawning ground during the spawningperiod but not six monthslater. Moreover,individual calls from malecod kept in tanksvaried a lot both in harmonicspacing and duration,from 42 to 79Hz and 0.11 to 1.25s, respectively. Such individual variation in callsis expected if femaleschoose mate on the basisof their calls.However, the resultsso far hasfailed to support thethird prediction, since no differences have been found between the callsof thetwo groups,nei- ther in harmonic spacing,duration, or temporal structure of the calls.

Introduction NortheastAtlantic cod consist of two stocks,the NortheastArctic, or "Arctic" cod, and the Norwegian coastalcod, or "Coastal"cod Roliefsen1934!. Arctic cod migratefrom the feedingareas in the BarentsSea to the spawningareas along the Norwegian coast and the mostimportant spawning areais off the Lofotenislands where the mainspawning occurs in Marchand April Bergstad& al. 1987!.Coastal cod inhabit coastal areas and fjords, migrate short distances and spawns in a large numberof fjordsalong the Norwegiancoast Rollefsen1954!, including off the LofotenIslands Hylen1964!. Both cod groupsspawn in Marchand April and maturespeciemens are syrnpatric during spawning at the major spawning grounds off the Lofoten Islands Nordeide 1998!.A controver- sialtopic during decades has been whether or notthe two codgroups interbreed, and a majorityof studiesconclude that they rarelydo seereferences in Nordeide& Pettersen1998!. If so,active part- nerchoice is required, and lekking has recently been suggested to bestdescribe the cod's mating system Hutchings & al. 1999;Nordeide & Folstad2000!.

Meller968! suggestedthat activepartner choice based on acousticcalls may be an behavioural mechanismwhich preventsinterbreeding between the two cod groups.The aim of this paperis to

Proceedingsfrom the international Iilrorkshopon the Applications of PassiveAcoustics to Fisheries 70 summarizethe first attemptsto test predictionsderived from Meller'shypothesis. The predictions are that i! recordingsfrom major cod spawning grounds should reveal sound with characteristics typical of codwhereas much less sound should be revealedoutside the spawningseason, ii! calls from individual cod should show considerable variation, and iii! calls from Arctic and Coastal cod should differ.

Material and methods To study soundat a majorspawning ground, recordings were carried out duringthe night at five stationsoff the LofotenIslands at 68 13,0'N14'38.7'E in NorthernNorway, during the spawningsea- son8 and9 April1997, and half a yearlater on 4 September1997 Nordeide8 Kjellsby1999!, The measuringhydrophone with a 32dB gain built-in preamplifierhad a totalsensitivity of -152dB re 1 V/pPa within the frequency range of 16 Hz to 2 kHz.In order to emphasizethe transient character of the sound the digital recordingswere analysedwith Short-time Fouiier Techniques STFT!,at the Norwegian DefenceResearch Establishment Nordeide & Kjellsby1999!.

To compare the callsfrom the two groups, recordingswere carried out in land-basedtanks in 1998 to 2001 Finstad,2002.!.Speciemens of the Arctic and Coastalcod were caught by trawl and trans- ferredto tankswhere recordings were carried out duringthe spawningperiod in 1998- 2001.The smallestmale used was 53 cmand the largestmale was 94 cm long,whereas the smallestand largestfemales were 51 cm and 104cm long,respectively. The average length of the five cod groups variedfrom 74.2crn to 84.0cm for males,and from 68.8crn to 90.5cm for females,Most recordings werefrom three6 m diameterfibreglass tanks, but a 3m diameterfibreglass tank wasalso used. Waterlevel was 1.4- 1.5m inall tanks.Recording equipment was a 1inch piezoceramicspherical hydrophonewith a sensitivityof -198dB ref 1V1@Pa, a Levell preamplifier type TA601 with 60 dB gain, and a SonyTCD-D100 digital tape recorder. In 1998,the recordingswere carried out with 12 speciemens six Coastal maies! in the experimental tank, whereas seven Arctic cod mates! where present in 1999.After the first yearsof experience we had identified two major problems: i! we were not ableto identifywhich cod producedthe calls,and ii! relativelyfew grunts had been recorded.In 2000and 2001we thereforechose to first recordgrunts with all cod in eachgroup kept together, to increasethe number of grunts. Thereafter,we split the groups of fish into a total of 10 smallersub-groups to increasethe minimumnumber of individualcod whichcould possiblypro- duce the grunts.The groups in 2000 and 2001 consistedof 8 males!,25 9 males! and 22 males! cod, respectively.The sub-groups consisted of from 4 males!to 16 1 males! cod,Towards the end of the spawningseason the fish werekilled. Examination of their otolithsby the Instituteof MarineResearch in Bergen,revealed that the recordingswere carried out with groupsand sub- groups consisting of i! only male Coastalcod with or without the presenceof Arctic females, ii! only male Arctic cod with or without the presenceof Coastalfemales, and iii! a mixture of Coastal and Arctic malesand females.These three alternative combinations are referred to as"Coastal-vocal'; "Arctic-vocal"and "Mix-vocal" groups respectively, since only malesproduce sound during the spawning period Brawn 1961c,Hawkins & Rasrnussen1978,see also Templeman& Hodder 1958, Engen & Folstad1999!. The number of individual cod statistical"N"! which could have produced the

Proceedingsfrom the internationalIVorkshop on the Applicationsof PassiveAcoustics to Fisheries 71 recordedgrunts were minimum 3 andmaximum 12 in the"Coastal-vocal" group, minimum 2 andmaxi- rnum 7 in the "Arctic-vocal",andminimum 4 and maximum22 in the "Mix-vocal"groups. Analysis by Avisoft-SASLabProv.3.74 provided estimates of harmonicspacing and duration of the grunts.Temporal structureof 78 recordedhigh quality grunts were analysed from oscillograms. Parameters included werenumber of downwardpeaks, time-intervals between peaks, and duration of the grunt.These parameterswere analysedby PrincipalComponent Analysis by the software"The Unscrambler"v. 7,5,

Results and Discussion Fieldrecordings provide support for the hypothesisthat acousticcommunication is importantduring cod spawning. Sound recordingsat the major spawning ground off the Lofoten Islands revealed a hushedhubbub of sound,at approximately40- 500Hz during the spawningperiod Fig.'la!. Much lesssound was revealed in September Fig, 1b! when no cod spawn and migratory cod had ernigrat- ed to the BarentsSea. Nordeide & Kjellsby999! arguesthat this soundmost likely is madeby spawningcod since! Thesound activity is highestin the frequencyrange where it hasbeen suggested cod communicate Chapman8 Hawkins 1973;Hawkins & Rasmussen1978!. ! The sound above 50 Hz had a transientcharacter as expected for cod grunts. ! More than ca. 50 million male cod spawnedoff the LofotenIslands in April 1997,and recordings were made where the Instituteof MarineResearch in Bergenlocated the highestdensities of spawningcod, ! Codtotally dominated,by constitutingmore than 98% by wet weight,the experimentaland commercialcatches in the areathe sevendays before, during and after the recordings Nordeide & Kjellsby1999!,

Variationin callsbetween individual cod kept in tanksis asexpected under the hypothesisthat acousticcommunication is importantduring female mate choice. Grunts from cod kept in tanks vary in harmonic spacing from 42 Hz to 79 Hz,and in duration from 0.11 s to 1.25 Table 1!.The two grunts with the lowest and highest harmonic spacing camefrom two different individuals, since they wererecorded from two differentsub-groups. The shortest and longestcalls were also produced by two differentindividuals. This shows that differentcod individualsmay grunt at different frequenciesand durations, but we cannot tell anythingabout each individual cod's possibility to vary their calls,

Table1. Mean,minimum and maximumvalues of frequencyand durationof gruntsfrom CC-vocal1, NAC-vocal2and the MIX-vocal3group. Number of grunts N! of frequency measurementsand duration measurementsdiffer becausesome of the durationmeasurements were difficult to perform due to background noise.The table is from Finstad002.!.

Frequency Hz! Duration s!

N Nlean Min Max N Mean Min Max

CC-vocal' 18 534 47 60 11 0.33 0.13 0.94

NAC-vocal' 11 55.7 50 60 11 0.31 0.1 1 0.74

MIX-vocal' 126 51.5 42 79 95 0.22 0.13 1.25

All grunts 155 52.1 42 79 116 0.24 0.11 1.25

Proceedingsfrom the International VYorkshopon the Applications of PassiveAcoustics to Fisheries 72 Grunts from groups and sub-groupsconsisting of CCmales and CCand NACfemales, based on otolith analyses Gruntsfrom groupsand sub-groups consisting of only NACindividuals, based on otolith analyses Gruntsfrom groupsand sub-groupsconsisting of both CCand NAC, both malesand females, based on otolith analyses

Theaverage harmonic spacing of gruntsfrom the Coastal-vocalgroups and Arctic-vocal groups were53.4 Hz and 55.7Hz, respectively, and the callsfrom the two cod groupslasted on average0.33 s and0.31 s, respectively Table l!,The differenceof 2.3Hz in harmonicspacing and 0.02 s indura- tion betweenthe two groups,is probablynegligible. The difference cannot be testedstatistically becausethe gruntsare not independentevents, since we werenot ableto tell whichcod produced eachcall, Moreover, the callsfrom the Mix-vocalgroups show no bimodaldistribution in harmonic spacingor duration,as is expectedif Coastaland Arcticcod callat two separatefrequencies or durations.In the multivariateanalysis of the temporalstructure of the grunts,the first andsecond principal componentexplained 45 and20%, respectively, of the total variation.However the analysisdid not clusterthe gruntsfrom Arctic-vocaland Coastal-vocalcod into two separategroups, as should be expectedif the temporalstructure of the two cod-groupsdiffered Finstad,2002.!.The hypothesis thus failedto passthe third test,since we havenot beenable to separatethe callsfrom the two cod groups. However,analysis of temporal structure will continue with lessrough analytical tools,

References Bergstad,O.AT, Jergensen, O. Dragesund 1987, Life history and ecology of the gadoid resourcesof the Barents Sea.- Fisheries Research 5:119-161.

Brawn, V.M. 1961c. Sound production by the cod Gadus callarias L.!; Behaviour 18:239-255.

Chapman,CJ. & A.D.Hawkins 1973. A fieldstudy of hearingin the cod,Gadus morhua L.- Journalof Comparative Physiology. 85: 147-167.

Engen,F. & I. Folstad 1999,Cod courtship song: a song at the expenseof dance?-Canadian Journal of Zoology 77:542-550.

Finstad,J.L, 2002, Acoustic callsof Norwegian coastal cod and North-EastArctic cod Gadusmorhua!. Cand.scient. thesis at the Departureof Fisheriesand MarineBiology, University of Bergen,Bergen,

Hawkins,A.D. & KJ.Rasrnussen 1978, The calls of Gadoidfish.- Journal of the MarineBiology Association of U.K. 58:891-911.

Hutchings,J.A,, T.D, Bishop & C.R.McGregor-Shaw 1999, Spawning behaviour of Atlanticcod, Gadus morhua: evidence of mate competition and mate choice in broadcastspawner.- Canadian Journal of Fisheries and Aquatic Sciences 56:97-104.

Hylen, A, 1964. Coastal cod and skrei in the Lofoten area. - Fiskeridirektoratets Skrifter Serie Havundersekelser, 13:27-42.

Proceedingsfrom the International Workshop on the Apptications o Passive Acousticsto Fisheries 73 Meller,D. 1968, Genetic diversity in spawningcod alongthe Norwegiancoast.- Hereditas 60:1-32.

Nordeide,J.T. 1998. Coastal cod andnorth-east Arctic cod do they mingleat the spawninggrounds in Lofoten?- Sarsia 83:373-379.

Nordeide,J.T. & I.Folstad 2000. Is cod lekkingor a promiscuousgroup spawner?- Fish and Fisheries 1:90-93,

Nordeide,J,T, & E,Kjellsby 1999. Sound from spawningcod at their spawninggrounds.- ICES Journal of Marine Science 56;326-332.

Nordeide,J.T.8 I.H.Pettersen 1998,Haemoglobin frequencies and vertebrae numbers of cod Gadus morhuaL.! off northernNorway - testof a populationstructure hypotheses.- ICES Journal of Marine Science 55;134-140.

Rollefsen,G. 1934. The cod otolith asa guideto race,sexual development and mortality,-Rapports et Proces-Verbauxdes Reunions du ConseilInternational Pour I'Explorationde la Mer 88:1-6.

Rollefsen,G. 1954.Observations on the cod and cod fisheries of Lofoten,- Rapportset Proces- Verbaux des Reunionsdu Conseil International Pour I'Exploration de la Mer,13640-47.

Templernan,W. & V.M.Hodder 1958.Variation with fish length,sex, stage of sexualmaturity, and season in the appearanceand volumeof the drummingmuscles of the swirnbladderin the haddock, Melanogramrnusaeglefinus L.!.-Journal of the FisheriesResearch Board of Canada.15:355-390,

Proceedingsfrom the international 8'orkshop on the Applications of PassiveAcoustics to Fisheries 74 Figure1. Recordings from a major spawningground off theI.ofoten Islands, a! duringthe spawning period in April and b} in Septemberwhen no cod spawn.Reprinted from ICFSJournaI of MarineScience Vol 56,Nordefde JT 8 E KjeIIsby, Sound from spawning cod at theirspawning grounds, 326-332, I ggg, by permission of thepublisher Academic Press. Applications~ ~ ofunderwater ~ ~acoustics data ~ ~in fisheries ~ management for spotted seatrout, Cynoscionnebulosus, in estuariesof South Carolina

Bill Roumillat and Myra Brouwer

Marine ResourcesResearch Institute, South CarolinaDepartment of Natural Resources, 217 Ft, Johnson Rd., Charleston, SC 29412. roumillatbOmrd.dnr.state.sc.us [email protected],state.sc.us

Introduction

The spotted seatrout, Cynoscionnebulosus, is an estuarine-dependentmember of the family Sciaenidae.Spotted seatrout are year-round residentsof estuariesalong the South Atlantic coast and spawning takes place inshore and in coastal areas McMichael and Peters, 'I 989; Luczkovich et al.,1999!, During summermonths, male spotted seatrout produce "drumming" sounds, this resulting from the contractionof the swimbladderby specializedmuscles which are seasonally hypertro- phied from the abdominal hypaxialis muscle mass Fishand Mowbray,1970; Mok and Gilmore, 'I983!. Direct involvement of sound production with spawning has been shown for this and other sciaenids Mok and Gilrnore,1983; Saucier et al., 1992;Saucier and Baltz,1993; Luczkovich et al., 1999!.By listening to these sounds during evening hours Holt et al. 1985! using hydrophone equipment we determined the locations,seasonality and diurnal periodicity of spawning aggregationsin Charleston Harbor Saucieret al., 1992;Riekerk et alunpublished data!.

Spottedseatrout are group-synchronous spawners with indeterminatefecundity. As such, they releasegametes in severalbatches over a protracted spawning seasonand total fecundity is not fixed prior to the onset of spawning Wallace and Selman,1981!. The spawning seasonextends from April through September along the South Atlantic and Gulf of Mexico coasts Overstreet,1983; Brown-Peterson et al., 1988; McMichael and Peters, 1989; Wenner et al1990; Saucier and Baltz, 1993!.As in other indeterminatespawning fish, annual fecundity in this speciesis dictatedby the number of oocytes releasedduring each spawning event batch fecundity, BF! and the number of such spawning events during the course of the season spawningfrequency, SF!. Estimationof annualfecundity AF!is intuitivelynecessary to determinethe contributionof an entirespawning season,and is madeeven more useful for fisheriesmanagement purposes if separatedby sizeclass or age cohort within a population Prager et al., 1987;Zhao and Wenner,1995!,

Behavior patterns basedon acoustic data enabled us to target females in imminent spawning condition,then carryout oocytecounts for batchfecundity estimation. Additional random sampling in other estuarineareas of the SCcoast provided the datanecessary to estimatespawning frequency

Proceedingsfrom the international Workshop on the Applications of PassiveAcoustics to Fisheries 76 for each of the three dominant age classes ages 1-3! in our waters,Ultimately, our annual fecundity estimatesfor each age classwill facilitate management of this speciesin South Carolina.

Estimationof batch fecundity Weconducted sampling for batchfecundity studies during two consecutiveafternoons fortnightly from the rniddleof April throughthe first weekof September1998, 1999 and 2000, We deployed a trammel net from a shallow water boat at pre-selected sites in CharlestonHarbor. Siteswere chosen based on proximity to known spawning locales establishedthrough hydrophone work. Water depth at the sampling sites ranged from 0.3 to 1.5 meters and sampling was conducted during the afternoon400-1800 h! high tide.Male spotted seatrout, identified by their drummingsounds, were measuredand releasedon site. Femaleswere brought back to the laboratory for processing. Werecorded standard life-history parameters for eachspecimen, preserved sagittal otoliths for agingand removedsections of the posteriorportion of eachovary for histologicalwork. In addition, whole ovariesthat evidenced oocyte maturation were fixed in 10% buffered seawaterformalin for enumeration of hydrated oocytes Hunter and Macewicz,1985!.

One hundred and thirty-five ovarieswere used to estimate batch fecundity of spotted seatrout aged 1-3. We re-weighed preserved ovariesto the nearest 0.01 g and randomly extracted 130-150mg aliquotsfrom three of eight possibleregions in the ovary fourper lobe!.We counted hydrated oocytesand usedtheir meannumber per subsampleto estimatethe total numberof oocytesin the ovary.To investigatethe relationshipsbetween batch fecundity and length,somatic weight ovary- free body weight!, and age we used linear regression on log-transformeddata. We used ANOVAon ranked data for comparisons of mean batch fecundity among ages,months and years.

Asexpected, we found a significantdifference in meanbatch fecundity among age classes Kruskal- Wallistest, P< 0.05!, Age 1 spotted seatrout, produced an averageof 145,452oocytes per spawn. Fishaged 2 and3 spawnedan averageof 291,123and 529,976oocytes per batch,respectively, Therefore,mean batch fecundity was compared among months and yearsfor each age classsepa- rately. There were no significant inter-annual or monthly variations in mean batch fecundity for any of the three age classes.

Pooling data acrossyears, total length explained 6996of the variability in spotted seatrout batch fecundity. Batch fecundity showed a similarly strong relationshipto fernale somatic ovary-free! weight but did not relate quite as strongly to age. The equations below describethese relationships:

Log BF = 3.134 Log TL! - 2.653 r' = 0.686! P<0.05

Log BF= 1.011 LogOFWT! + 2.709 r' = 0.675! P<0.05

Log BF = 0.288 Age! + 4.844 r' = 0.586! P<0.05

Proceedingsfrom the International 5'orkshop on the Applications of PassiveAcoustics to Fisheries 77 Calculationof spawningfrequency Weobtained samplesfor spawning frequency determination during the courseof stratified random trammel net sampling in several estuariesalong the SCcoast. Eachstratum was sampledonce a month throughout the year during ebbing tide. However,we only used spotted seatrout samples obtained during summer months May through 31 August! for this study.

Wecalculated monthly spawning frequencies for ageclasses 1-3 using the postovulatoryfollicle methodof Hunterand Macewicz985! wherespawning frequency is the inverseof the proportion of ovarieswith postovulatoryfollicles POF!< 24h oldamong mature and developingfemales.

Overa decadeof samplingthe CharlestonHarbor estuarine system we haveobserved that, among femalescaptured in shallowwater during the spawningseason, oocyte maturation begins at about 1200h. Fromrnid to late afternoonthese females leave the marshedge for deeperwater to spawn. Ourhydrophone surveys have indicated that spawningtypically begins around 1800 h andceases around2200 h. Femalesthen returnto feedinggrounds near the marshwhere they are available to our samplinggear. Knowledge of this reproductivebehavior enabled us to targetspotted seatrout in the rnid-tateafternoon specifically to capturefish with late-maturingoocytes for batchfecundity estimation.Females that were backin the shallowsafter havingspawned the previousevening were avaiiablefor captureduring daytime sampling. In addition,we carriedout round-theclock sampling on two occasionsduring the 2000-spawning season. Samplesfrom this effort allowed for the calibration of criteria used to age POFs.

A totalof 941fernale spotted seatrout, captured during the spawningseasons of 1998,1999and 2000 was examinedto determine spawning frequency. Femalesused to determine SFranged in lengthfrom 240mrn to 542 mm mean340 rnm! and in agefrom 1 to 5. However,97'Yo of the speci- rnensbelonged to ageciasses 1-3. Thus, reproductive parameters are presented only for theseage classes.

Smallsample sizes prevented calculation of monthlyspawning frequencies for eachage class by year.Thus, data for all three yearswere pooled to obtaina singlemonthly spawning frequency esti- mateby ageclass Table 1!,Overall, spotted seatrout ages 1-3 in SouthCarolina spawned every 4,4 daysor roughly 28 times during the reproductive season.

Estimationof annual fecundity Wecalculated monthly egg production MEP!by multiplyingthe monthlyspawning frequency by the meanmonthly batch fecundity for eachspecimen. Because not all age-1female trout were matureat the beginningof the spawningseason, the fractionof matureage-1 females obtained from a previousstudy Wenner,unpublished data! was used to refine the MEPestimate. MEP esti- rnateswere then summedto arriveat an annualfecundity estimate for eachage class Table 1!.We usedlinear regression on log-transformeddata to investigatethe relationshipbetween annual fecundityand age and thus predict annual fecundity for spottedseatrout aged 4 and5. Age

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 78 explained98% of thevariability in annualfecundity for ageclasses 1-3. From this relationship, the predictedannual fecundities for ageclasses 4 and5 were43,752,211 and 101,157,945, respectively. Table1. Fecundityparameters for C.nebulosus ages 'I - 3from South Carolina estuaries. BF= batch fecundity in numbersof oocytes;SF= spawning frequency expressed asthe numberof spawnsper month; MEP= monthly eggproduction= BF"SF!%mature. Annual fecundity is the sum of incanmonthly MEP values for each year classand represents the total number of oocytesproduced by any given female from 1 lViayto 31August. Numbers in parenthesesindicate sample size,

Age Month Mean BF SF % mature Mean MEP 1 May 117,760 2! 4,18 89! 78,6 386,897 June 135,403 6! 9AO 66! 94.0 1,196,418 July 141,237 6! 6.54 85! 97.0 895,978 August 176,594 8! 4.57 29! 100 807,035 Annual fecundity = 3,286,328

May 280,724 4! 6.80 14! 100 1,908,926 June 307,322 0! 7.60 9! 100 2,335,650 July 370,170 ! 9.04 8! 100 3,346,337 August 307,195 ! 6.34 4! 100 1,947,620 Annual fecundity = 9,538,533

May 487,475 3! 7.42 6! 100 3,6'l 7,061 June 519,630 ! 9.12 3! 100 4,739,027 July 765,911 ! 3.1 0! 100 2,374,325 August 590,994 ! 11.61 8! 100 6,861,439 Annual fecundity = 17,591,852

Weexpanded annual fecundities relative to theabundance of eachage class in oursamples for the threeyears of thestudy. We estimated that the overallaverage contribution from age 1 fishto the reproductiveoutput for the season was approximately 25% whereas fish aged 2 and3 contributed 34'/o and 19% of oocytes,respectively. Ages 4-5, which comprised less than 396 of specimenssam- pled,each contributed about 11% based on predictedannual fecundity values.

Discussion Attemptsat estimatingthe spawning potential of a specieshave rarely incorporated spawning behaviorinto the methodologyused in capturingthe animalsprimarily due to limitationsof the samplinggear, Moreover, estimates of fecundity batch numbers and spawning frequencies! have reliedon the assumption that the collectionof a reasonablesize range of adultfemales during

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 79 establishedspawning periods should be sufficientto coverall phasesof reproductiveactivities DeMartini and Fountain,1981; Lisovenko and Adrianov, 1991!. Our choice not to use the relative occurrenceof hydratedoocytes to estimatespawning frequencies was based on our knowledgeof the spawningbehavior of this species.Previous work conductedin the studyarea Riekerket al., unpublisheddata! established the locationand timing of spawningactivities allowing us to focus our samplingefforts in shallowwaters near known spawninglocations to collectfemales with fate maturing oocytes. This constant loss of late maturing femalesfrom the fish available to our nets in shallowwater would have decreased the relativeabundance of this maturitystage in our samples, Therefore,using the relativenumber of late maturingoocytes for spawningfrequency calculations would haveresulted in an underestimateof spottedseatrout reproductive potential.

Becauseobtaining representative numbers of animalswith late-maturingoocytes is not often feasi- ble,researchers have relied on the relativeabundance of postovulatoryfollicles to calculatespawn- ing frequencies i.e.Hunter and Goldberg,1980; Hunter et a/,,1986;Brown-Peterson et al1988; Fitzhughet al.,1993; Taylor et a!1998;Macchi and Acha,2000; Brown-Peterson and Warren,2001; Nielandet al2002!.Thismethod has depended on the abilityto time the disappearanceof these structures.Our diurnal sampling of reproductivelyactive spotted seatrout during warmwater conditions allowedus to establishcriteria to accuratelyestimate the age of POFsthroughout the spawning season.Furthermore, we wereable to verifyour assessmentsby samplingaround the clockon two occasionsto collectfish overthe time period irnrnediatelyfollowing a spawn.This would not havebeen possible had we failed to establishand verify the locationof spawningaggregations with the use of passiveacoustics.

Themain impetus behind this study was to establishrealistic annual fecundity estimates by age classthat couldbe usedin predictivemodeling of the spottedseatrout population in coastalSouth Carolina.Herein, we presentequations relating fecundity to lengthand agethat can be usedto estimatethe reproductivepotential for eachage classof spottedseatrout along the SouthCarolina coast.The average season-long oocyte output of age 1 fishwas one-third that of age 2 -3.28M vs. 9.5M!,When analyzed in relationto the abundanceof the other ageclasses,age 2 fishwere predict- edto contributemore overall fertilizable oocytes to the environment.Even though the average age 3 fishproduced almost twice asmany oocytes 7,5 M! than the averageage 2, the abundanceof age 3 trout in our estuarinesamples was low enough to make their overallcontribution to a season'sspawning effort only half that of 2 year-olds.This exemplifiesthe potential for error in estimating reproductiveoutput based on the abundance of yearclasses, especially that ofyounger fish,

Acknowledgements Wethank membersof the InshoreFisheries Section of the SouthCarolina Department of Natural Resourcesfor assistingin fielddata collection throughout this study Dr.C.Wenner, J.Archambault, H.von Kolnitz,W. Hegler, E. Levesque, L Goss, C. McDonough, C.Johnson, A. Palmer!, Dr.C. Wenner, H. vonKolnitz and E. Levesque conducted age assessments. Histological processing was provided by C. McDonough,R. Evitt, A. Palmer and W. Hegler. C. McDonough, T. Piper, K. Maynard and R.Evitt assisted withoocyte counts.J. Archarnbault coordinated data managementand Dr.C.Wennerand E. Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics ta Fisheries 80 Levesqueprovided heipful suggestions on the manuscript.Funding for this studywas provided by the National Marine FisheriesService under MARFINgrant ilNA77FF0550,

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Holt,G J.,S.A. Holt andC. R. Arnold. 1985. Diel periodicity of spawningin sciaenids.Mar Ecol.Prog. Ser. 27:1-7.

Hunter,J.R., and S.R.Goldberg. 1980. Spawning incidence and batchfecundity in northernanchovy, Engraulis mordax. Fish. Bull. 77:641-652.

Hunter,J. R., and B,J, Macewicz. 1985. Measurement of spawningfrequency in multiple spawning fishes.In: An egg productionmethod for estimatingspawning biomass of pelagicfish: application to the northernanchovy Engraulis mordax R.Lasker, ed.! p. 79-94.U. 5, Dep. Comrner., NOAA Tech. Rep, NMFS 36.

Hunter J.R.,B J.Macewiczand H.R.Sibert.1986The spawning frequency of skipjack tuna, Katsuvvonuspelamis, from the South Pacific. Fish. Bull, 84:895-903.

Lisovenko,L.A., and D. P. Andrianov, 1991. Determination of absolutefecundity of intermittently spawning fishes.Voprosy ikhtiologii 31;631-641.

Luczkovich,J.J., H,J. Daniel III and M.W.Sprague. 1999, Characterization of criticalspawning habitats of weakfish,spotted seatrout and reddrum in PamlicoSound using hydrophone surveys, Final report and annual performance report F-62-2and F-62-2. North CarolinaDepartment of Environment and Natural Resources,Division of Marine Fisheries,Morehead City, NC 28557.

Macchi,G. Jand E.M.Acha. 2000. Spawning frequency and batchfecundity of Brazilianmenhaden, 8revoortiaaurea, in the Riode la Plataestuary off Argentinaand Uruguay.Fish. Bull. 98:283-289,

McMichael,R. H., and K.M.Peters. 1989. Early life-history of spottedseatrout, Cynoscion nebulosus Pisces:Sciaenidae!, in TampaBay, Florida, Est. 12:98-110. Proceedingsfrom the InternationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 81 Mok,H. K., and R.G. Gilmore.1983. Analysis of soundproduction in estuarineaggregations of Pogoniascrornis, Bairdiella chrysoura, and Cynoscionnebulosus Sciaenidae!.Bull. Inst, Zool.,Acad. Sinica Taipei! 22:157-186.

Nieland,D, L., R, 6 Thomas,and C.A. Wilson. 002!. Age,growth and reproductionof spotted seatrout in Barataria Bay, Louisiana. Trans. Arn. Fish. Soc. 131:245-259.

Overstreet,R.M. 1983. Aspects of the biologyof the spottedseatrout, Cynoscion nebulosus, in Mississippi.Gulf Res.Rep. Suppl, 1;1-43.

PragerM.H., J. F O'Brien, and S. B. Saila. 1987. Using lifetime fecundity to comparemanagement strategies:a casehistory for striped bass,Am.J. Fish.Manag. 7:403-409.

Riekerk,G. H, M., S.J. Tyree, and W.A. Rournillat. 1997, Spawning times and locationsof spotted seatroutin the CharlestonHarbor Estuarine System from acousticsurveys. Final Report to CharlestonHarbor Project, Bureau of Oceanand CoastalResources Management, South Carolina Department of Health and Environmental Control, Charleston.

Saucier,M. H., D.M. Baltz, and W.A. Rournillat. 1992. Hydrophone identification of spawningsites of spotted seatrout Cynoscionnebulosus Osteichthys: Sciaenidae! near Charleston,South Carolina.N. Gulf Sci.12;141-145.

Saucier,M. H,, and D,M. Baltz. 1993. Spawning site selection by spottedseatrout, Cynoscion nebulosus,and black drum, Pogoniascromis, in Louisiana,Env, Biol. Fish.36:257-272.

Taylor,R.G., H.J. Grier and J.A.Whittington. 1998.Spawning rhythms of common snook in Florida.J. Fish Biol, 53:502-520.

Wallace,R.A,and K, Selman.1981. Cellular and dynamicaspects of oocytegrowth in teleosts.Amer. Zool. 21: 325-343.

Wenner, C.A., W.A. Roumillat, J. E, Moran Jr., M.B. Maddox, L.B. Daniel III and J.W. Smith. 1990. Investigationson the life history and population dynamics of marine recreationalfishes in South Carolina:part 1. FinalReport F-37. Marine Resources Research Institute, MarineResources Division, South CarolinaDepartment of Natural Resources,217Ft. Johnson Rd.,Charleston, SC 29412.

Wenner,C.A. and B.Zhao. 1995. Stock assessment and fishery rnanagernent of the spottedseatrout, Cynoscionnebulosus, on the South Carolinacoast. Marine ResourcesResearch Institute, Marine ResourcesDivision, South CarolinaDepartment of Natural Resources,217Ft,Johnson Rd., Charleston, SC 29412

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 82 ~ ~ ~ Soniferous Fishes of Massachusetts

Rodney Rountree',Francis Juanes',and Joseph E. Blue'

'Schoolfor MarineScience and Technology, UMASS Dartmouth, 706 Rodney French BlvdNew Bedford, MA 02744-1221 [email protected]

'Department of Natural ResourcesConservation, University of Massachusetts,Amherst, MA 01003

'President,Leviathan Legacy, Inc.,3313 Northglen Drive, Orlando, FL 32806 jblue46498Oaol.corn

Introduction

Sincethe seminalwork of Fish and Mowbray 970!, little advancement has been made towards the study of soniferousfishes from the marine waters of the Northeastern United States.A review of the iiteraturesuggests at least51 fishesare vocal in NewEngland waters Table1!, although many of thesespecies are uncommon stragglers to thesewaters. Spontaneous sound production is known from onlyabout half of thesespecies, However, laboratory studies are often hamperedby the difficulty of maintaininghealthy specimens, and the difficultyof inducingnatural behaviors such as spawningunder confinement. This is further complicated by the fact that manyfish areprimarily vocalduring the spawningseason, and may not vocalizeuntil maturity,and becausevocal behavior is usuallylimited to males e,g,,hadcfock and weakfish!. The objectives of this studywere to conduct a pilotfield surveyof soniferousfishes in Massachusetts'swaters to determinewhat speciesare vocaland examine temporal patterns in vocalbehavior. However, because of the unexpectedfind- ing of widespreadcalls of the stripedcusk-eel on CapeCod, this paperwill focuson this enigmatic species.

Table 1 below!,Partial list of speciesknown to be capableof sound production based on field and/or laboratory studies,andwhich occur at leastseasonally in HewEngland Long Island to IVlaine!estuarine and shelf waters Fishet al.1952,Fish and Mowbray1970, Hawkins and Rasrnussen1978, Tavolga 1980, IVlann et al. 1997!, "Soundproduction capability assumed based on the presenceof anatomicalstructures usually associated with vocalization. All specieswere not necessarilysubjected to both mechanicaland electrical stimulation in the Fish et al, 1952and Fish and Mowbray 1970studies!,

Scientific name Common name Sounds produced spontaneous- ly ! or under either mechanical M! or electrical E! stimulation

Anguillidae American eel Weak:M,Eand 5 Anguilla rostrata American eel Weak: M,E and 5 Clupeidae American eel Weak: M,E and 5 Brevoortia tyrannus Atlantic menhaden Weak; M

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 83 Clupea harengus Atlantic herring Weak; M,E Opisthonema oglinum Atlantic thread herring Weak: M,E Gadidae Brosme brosme Cusk ? Gadus morhua Atlantic cod Strong: M,S Melanogrammusaeglefinus Wad dock Strong: S Merlucci us bili nearis Silver hake Weak: M Pollachi us virens Pollock Weak; M Urophycis chuss Red hake Weak: E Urophycis regia Spotted hake Weak: E Ophidiidae 'Lepophidium profundorum Fawn cusk-eel ? Ophidion margi natum Striped cusk-eel Strong: S Batrachoididae Opsanus tau Oystertoadfish Strong; 5 Dactylopteridae Dactylopterus voli tans Flying gurnard Strong: M Trig lidae Prionotus carolinus Northern searobin Strong: M, 5 Prionotus evolans Striped searobin Strong: S Cottidae Myoxocepha!us aenaeus Grubby Weak: M,E Myoxocephalus octodecemspinosus Longhorn sculpin Strong: M,S Percichthyidae Morone saxatilis Striped bass Moderate: M,E Serranidae Centropristis stri ata Black sea bass Weak: M,E Pomatomidae Pomatomus saltatrix Bluefish Weak: M,E Carangidae Alectis ciliaris African pompano Strong: M Caranx crysos Blue runner Moderate: M,S Caranxhippos Crevalle jack Strong; M,S Caranx latus Worse-eyejack Strong: M,E,S Caranx ruber Barjack Strong: M,S Chloroscombrus chrysurus Atlantic bumper Moderate; M,E Se/enesetapinnis Atlantic moonfish Strong: M Se/ene vomer Lookdown Strong: M Seriola dumerili Greater amberjack Moderate. 5 Lutjanidae Ocyurus chrysurus Yellowtail snapper Weak: M,E,S Lutj anus griseus Gray snapper Weak M,E Haemulidae Orthopristis chrysoptera Pigfish Strong; M,S Sparidae 5 tenotomus chrysops Scup Weak: M Sciaenidae Bairdiellachrysoura Silver perch Strong: M,S Cynoscion nebulosus Spotted seatrout ? Cynoscion regalis Weakfish Strong: M,S

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 84 Leiostomus xanthurus Spot Moderate: M,E,S Menticirrhus saxatilis Northern kingfish Weak: M Micropogon undulatus Atlantic croaker Strong; M,S Pogonias cromis Black drum Strong: M,S Labridae Tautoga onitis Tautog Moderate: E,S Tautogolabrus adspersus Cunner Weak: E Balistidae Aluterus schoepfi Orange filefish Moderate: M,E,S Balistes capriscus Graytriggerfish Moderate: M,E,S Monacanthus hispidus Planehead filefish Moderate: M,E Ostraciidae Lactophrys guadricornis Scrawled cowfish Moderate: M Tetraodontidae Chilomycterusschoepfi Striped burrfish Moderate: M,E 5 phoeroides maculatus Northern puffer Moderate: M Molidae Mola mola Ocean sunfish Strong: M

Methods Recordingsof fish soundswere made at 12 differentsites across Cape Cod at leastonce between Juneand October 2001. However, the primary sampling location was the Cotuit town landing whichwas sampledon 18different dates, including 5 dateson whichmonitoring was conducted overthe dielcycle. Except for the diel studies, most sampling was conducted around sunset, usually beginning 1 to 2 hours before sunsetand continuing for 2 to 3 hoursafter sunset.To obtain infor- rnation on the daily pattern of fish calls,diel studies were conducted on five different dates at Cotuit town landing. Forthese studies, sounds were recordedapproximately from 1300-1400h, 1900-2300 h, 0100-0200h, and 0400-0600 h, corresponding to afternoon,sunset, night, and sunriseperiods, respectively.Low cost hydrophones Arretec, PB 3098 Bletchley, Milton KeynesMK2 2AD, United Kingdom! were deployed from docks,piers, jetties and small boats and recordedto a hi-fi VCR. Occasionally,recordings were made to a Sonyhand-held tape recorder model TCM-929!.In addition,whenever possible, video recordings were made simultaneously to the VCR using a hand- deployedunderwater video camera equipped with infraredlights modelsmade by VistaCam, 9911 Goodhue St. NE,Blaine MN 55449,and Aqua vu, NatureVision lnc.,213 NW 4th StBrainerd, MN 56401!.Sounds were captured to a PCwhile playingback from a VCRusing Cool Edit 2000 made by SyntrilliumSoftware Corporation!, Some spectral analyses were also conducted using Signal for Windows Engineering Design,43 Newton St, Belmont, MA 02478!. To quantify call frequency, 1-4 hoursound samples were divided into 10-minutesegments and a randomlyselected 2 minute soundclip wasobtained from each. Callsfor toadfish,striped cusk-eel and searobinswere identified and counted. Referencesound clips of unknown callswere made and usedto make counts of unknown sounds by type e.g"grunt-A",etc.!.

Results

Over53 VHSand 12cassette tapes comprising over 160hours of recordingswere collected. Calls of stripedcusk-eels, Ophidian marginatum, oyster toadfish, Opsanus tau, and stripedsearobin, Prionotus Proceedingsfrom the internationalWorkshop on theApplications of PassiveAcoustics to Fisheries 85 evolans, dominated the observations. Several unidentified calls were also common. We are continuing our efforts to identify these calls. In addition, various sourcesof natural and man-made noise werealso recorded including: outboard boats, barges jet-skies, dock noises, fishing noises, depth- finders,and gasrelease from sediments.Based on the occurrenceof vocalchoruses, we found sunset spawning aggregations of the striped cusk-eelsat eight of 12 locationssampled acrossthe length of Cape Cod,including two sites BarnstableHarbor and ProvincetownHarbor! on the north shore.Cusk-eels were recorded from the first sampling date June11! through the end of August, but abruptlystopped by early September, Oyster toadfish were also already calling at the startof the field season,but sunsetchoruses had ceased by mid-July.Striped searobin calls were not associatedwith sunset, but occurredthroughout the night, Searobin calls were most frequent in August andSeptember but werestill present in October.The cusk-eel sounds recorded in MAare nearly identicalto stripedcusk-eel sounds recorded by the first authorunder laboratory conditions in New Jersey Mann et al. 1997!,and morerecent sounds recorded in the Fieldand attributed to stripecusk- eelsin NarragansettBay Perkins2002! and North Carolina Sprague and Luczkovich 2001!. Our attributionof thesesounds to the stripedcusk-eel is further validatedby the captureof a 170mm TL specimenwhile recordingsounds in Cotuit,MA in July2001, and by subsequentsightings of a larger individual later that same month. Cusk-eels can sometimes be observed in the shallows at night with the aid of a spotlight Rountree,pers. Observ.!. In Figure1, chatters vary in relativeampli- tude and rangeform 8 to 16 pulsesand calltimes of 275msec to 730msec. The dominant frequency was1098-1866 Hz comparedto the toadfishcall at the beginningof the sequenceat 171-585 Hz!. A samplecall recordedfrom Provincetown,MA on August23, 2001 is shownin Figure2. This call is considerablylonger 1 pulses,1,715 msec! than thosein Figure1, but is still well within the rangecharacteristic of the species Mann et a!,1997,Sprague and Luczkovich2001!, A singlerepre- sentativepulse has most energy between 914 and 1524Hz Fig.2!.

Stripedcusk-eel calls can be heardsporadically throughout the day,but callsclearly become more frequentat sunset Fig.3!. Peaknumber of callsoccurred between 20 to 60 minutesafter sunset, anddeclined to nearzero within two hours.In contrast, the oystertoadfish calls more frequently duringthe day, but alsoexhibits a strongincrease in activityassociated with sunset Figure 4!. Althoughdata are more limited,peak activity occur 1-2 hours after sunset, with moregradual declines through the night compared to the striped cusk-eel,

Proceedingsfrom the international Workshopon the Appiications of PassiveAcoustics to Fisheries 86 Discussion It issignificant that the stripedcusk-eel was the most frequently heard and widely distributed speciesencountered during this studyas it haspreviously been thought to occurfrom BlockIsland southto Florida,with only rarestragglers occurring as far north asCape Cod Colletteand Klein- MacPhee2002!, despite extensive faunal surveys in theregion over several decades. This finding nicetydemonstrates the usefulnessof passiveacoustics as a supplementto traditional survey methods,particularly for speciesdifficult to samplein otherways. The seasonal and daily pattern of stripedcusk-eel vocal activity agrees with publishedlaboratory findings IVlann et al.1997, Sprague andLuczkovich 2001!. Striped cusk-eels were already chorusing by rnid-Junewhen sampling began,but hadstopped by mid-Septemberin good agreement with previousstudies, Call frequency increasesrapidly at sunsetdeveloping into a loudchorus that lastsfrom 1 to2 hours Fig. 3!. Captivecusk-eels have been observed to chorusafter sunset as part of courtshipand spawning behavior Mann et al. 1997,Rountree and Bowers-Altman2002!. We believe that our observations suggest widespread spawning of striped cusk-eelswithin estuariesof both the north and south shoresof CapeCod. The species'cryptic nocturnal behavior, and habit of remainingburrowed duringthe day likely account for thefailure of previousresearchers using conventional sampling gears i.e.,trawls and seine sampling mostly limited to daylighthours! to recognizeits importance to the region. At this time the northernrange of the stripedcusk-eel must be reconsidered.How much fartherup the cost the speciesextends is unknown. It is notable that Geoghegan etal. 998! recordeda singleadult striped cusk-eel at Seabrook,New Hampshire and argued that it mightrep- resenta smallfocal population. Therefore, we suspect that reproducing populations of thisspecies mayoccur at leastto NewHampshire waters. However, the scarcityof ophidiideggs in ichthyoplankton surveysof the region is puzzling e.g.,Fahay 1992! and future studies on the distribution and ecologyof thiscryptic species are needed. Boat sounds were problematic during the day, some- timesoccurring during 50-99/oof the soundsample clips. Duringthese times, sounds of fishes couldnot beheard above the boat'snoise. Boat noise was rare during the evening hours. The impactof boat-associatednoise on the behaviorof fishesis poorly known, but it hada strong impacton ourability to recordday-time fish sounds, It ishoped that the newly available archive of fishsounds originally published by Fish and Mowbray 970! andrecently repackaged by the University of Rhode Island Rountree et al. 2002! will aid in the identification of the unknown calls recorded on Cape Cod. In summary this study hasdemonstrated the usefulnessof even low-cost passiveacoustics technology as a tool to survey estuarineand marine fishes. Information on the temporaland spatial patterns of fishvocal behavior can be used to gaininsight into temporal and spatialpatterns in habitatuse patterns by vocal species. In particular,identification of spawning habitatsthrough passiveacoustics surveys is promising.

Acknowlecigernents MeganHendry-Brogan and KatieAnderson are thanked for diligent workin both the field and labo- ratoryto collectand process fish sound data. This project received major funding from the Northeastand Great Lakes National Undersea Research Center, which aiso provided extensive Iogis-

Proceeclingsfrom the internationalWorkshop on theApplications of PassiveAcoustics to Fisheries 87 tical support. TheWoods Hole Sea Grant College Program also provided supporting funds.

TheSounds Conservancy, Quebec-Labrador Foundation/Atlantic Center for the Environmentprovid- ed a stipend for Megan'sfieldwork.

Literature Cited

Collette, B.B.,and G. Klein-MacPhee. eds.!. 2002. Bigelow and Schroeder'sFishes of the Gulf of Maine. 3rd Edition.Smithsonian Institution Press, Washington, D.C. 748 p.

Fahay,M.P. 1992. Development and distributionof cuskeel eggs and larvaein the middleAtlantic Bightwith a descriptionof Ophidionrobinsi n.sp. Teleostei;Ophidiidae!. Copeia 1992!:799-819.

Fish,M.P., A.S, Kelsey, Jr., and W.H. Mowbray, 1952. Studies on the productionof underwatersound by North Atlantic coastal fishes.J. Mar. Res. 11:180-193.

Fish,M.P., and W.H,Mowbray. 1970. Sounds of WesternNorth Atlantic fishes. Johns Hopkins Press, Baltimore, MD. 205 p.

Geoghegan, P.,J.N. Strube, and R.A. Sher. 1998. The first occurrence of the stripedcusk eel, Ophidion marginatum Dekay!,in the Gulf of Mexico. Northeastern Naturalist 5!:363-366.

Hawkins,A.D. 1986, Underwater sound and fish behaviour.pp. 114-151. In: The Behaviourof Telcost Fishes. ed. T J. Pitcher!. Groom-Hellm. London.

Hawkins,A D.,andKJ. Rasmussen.'I978 The calls of gadoidfish.J. Mar. Biol. Ass. U K,58891-911.

Mann,D.A., J. Bowers-Altrnan, and R.A.Rountree. 1997. Sounds produced by the stripedcusk-eel Ophidionmarginatum Ophidiidae! during courtshipand spawning.Copeia 1997!:610-612.

Perkins,P J.2002. Drurnrning and chattering sounds recorded underwater in Rhode Island. Northeastern Naturalist 8!;359-370.

Rountree,R.A. and J.Bowers-Altman. 2002. Soniferous behavior of the stripedcusk-eel, Ophidion marginatum, Bioacoustics 12/3!:240-242.

Rountree,R.A., PJ. Perkins, R.D. Kenney, and K.R,Hinga. 2002. Sounds of WesternNorth Atlantic Fishes: Data rescue. Bioacoustics 12/3!:242-244.

Sprague,M.W. and J.J. Luczkovich. 2001. Do striped cusk eels, Ophidian marginatum Ophidiidae! pro- ducethe'chatter'sound attributed to weakfish,Cynoscion regalis Sciaenidae!? Copeia 2001 !: 854-859,

Tavolga,W.N. 1980, Hearing and sound production in fishesin relationto fisheriesmanagement. P,102-123,In: Bardach,J.E., J.J. Magnuson, R.C.May, and J.M.Reinhart eds.!,Fish Behaviorand its use in the captureand cultureof fishes.ICLARM Conference Proceedings 5, 512 p. InternationalCenter for LivingAquatic Resources Management, Manila, Philippines.

Proceedingsfrom the internationalI/I/orkshop on the Applicationsof PassiveAcoustics to Fisheries 88

Figure3. Dailypattern of stripedcusk-eel, Ophidion marginatum, calls collected on two dotes027 Juneand 2 3July 2007!. All callsheard within 2 minutessound clips were counted, Sample clips were taken randomly from within 70-minutesample bins. The vertical arrow marks the time of sunset as obtained from a handheld GPS.

Figure4, Dailypattern of oyster toadfish,Opsanus tau, ca!1on June 20 27,2007.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 9P Themating behaviour ofAtlanti««od Gorfua morhuo!.

SherrylynnRowe and JeffreyA, Hutchings

Department of Biology,Dalhousie University, Halifax, Nova Scotia,83H 4J1,Canada. rowesC>is2,dal.ca

Introduction Atlanticcod Gadusmorhua! is a marinedemersal fish that inhabitscool-temperate to subarctic waters from inshore regions to the edge of the continental shelf on both sidesof the North Atlantic Scottand Scott 1988!. Atlantic cod has been harvested throughout its rangefor hundredsof years and yet despitebeing of theoreticalinterest and practicalimportance, very little hasbeen learned about its reproductive behaviour during this period.

Throughout the Atlantic,there are many recognizedcod stocks,each of which has its own set of characteristics.Age at maturityvaries between 2 and7 years Myers et a/.1997!and Atlanticcod typicallyspawn over a periodof lessthan 3 months Brander 1994; Chambers and Waiwood 1996; Kjesbuet al, 1996! in water depth ranging from tens Smedbol and Wroblewski 1997!to hundreds of metres Brander1994; Morgan et ai, 1997!.Individuals are assumed to breedannually and Atlantic cod areconsidered to be batchspawners as only 5-250ioof a femalesegg complementis released at anytime during her3- to 6-weekspawning period Chambersand Waiwood 1996; Kjesbu et ai. 1996!.Individual females release hundreds of thousands,often millions,of tiny eggs.2-1.6 mm in diameter!,for which no parental care is provided,directly into oceanic waters Scott and Scott 1988!.

Thelimited information available on Atlanticcod spawning behaviour suggests complex mating patterns,the occurrenceof behaviouraland acousticdisplays by males,mate choice by females,and alternativereproductive strategies among males Brawn1961a; Hutchings et ai, 1999!,However, there is no information on the selective causesand consequencesof these behaviours,nor the structure of the mating system Nordeide and Folstad 2000!,

Ourresearch employs a quantitativeapproach to understandcauses and consequencesof variation inthe mating system of Atlanticcod at the individualand population levels, We are incorporating both detailed experimental studiesin the laboratory and observations of cod in the wild. Our researchinvolves several components including the following: i! mating systemstructure and identificationof behaviouraland phenotypic correlates of reproductivesuccess, ii! intra- and inter-pop- ulationvariation in soundproduction during spawning, and iii! patternsof variationin drumming muscle mass.

Proceedingsfrom the International!4'orifshop on the Appiicationsof PassiveAcoustics to Fisheries 91 Laboratoryobservations of spawningAtlantic cod Thelaboratory component of our researchinvolves cod from two spatiallydistinct areas in the NorthwestAtlantic: Southwest Scotian Shelf and SouthernGulf of St.Lawrence, identified by the NorthwestAtlantic Fishery Organization NAFO! Divisions as 4X and 4T,respectively. Mature adults fromeach stock were collected and taken to a 680rn' aquariumat Dalhousiewhere spawning occurred.Groups of fish representingeach stock were examined separately during their temporally distinctspawning periods. Cod were maintained at densitiessimilar to thosein nature approxi- mately0.1 fish perm'; Rose1993; Morgan et a/. 1997!and spawningbehaviour of individually taggedfish wasrecorded by videotapeand visualobservation. A hydrophonewas placed in the centreof the tankand soundswere recorded continuously during the spawningseason, A random sampleof fertilizedeggs was collected daily and pedigreeanalysis is being undertakenusing rnicrosatelliteDNA. In additionto providinginformation on individualmale and femalereproduc- tive success,the DNAanalyses, coupled with behavioural observations,will allow us to determine phenotypic and behaviouralcorrelates of reproductive success.

Observationsto datesuggest that strongdifferences in spawningbehaviour exist between and within Atlanticcod populations.A strongdominance hierarchy, territoriality, and high levelsof aggressioncharacterized males from 4T but this wasn'tthe casefor malesfrom 4X amongwhich very little aggressivebehaviour occurred and no fish heldterritories for prolongedperiods. However,preliminary examination of the soundrecordings have suggested that 4Xfish aremore vocal than 4T fish. Similarly,we found that for both females and males,4Xfish had heavier drumming musclesrelative to their body weight drumming muscle somatic index! than those from 4T Figure 1!,

Wealso observed intra-population differences in behaviour,particularly for fish from 4T,We found that the aquariumwas dominated by 3-4 malesthat fiercelydefended territories during the spawning seasonand frequently engaged in courtshipactivity. Other males were much more passive and it seemsthat somespecialized as sneakers in spawningevents and evenmight havebeen imitating femalesto gainaccess to maleterritories. Initial observationssuggest that fish whichwere dominant and engagedin mostcourtship activity wereones with the largestdrumming muscle somatic index andwere not necessarilythe largestin length!, Weare waiting for resultsof the pedigree analysisto determinethe wayin whichthese behaviours might haveinfluenced reproductive success.

Field observationsof variation in Atlantic cod drumming inusclemass Soundproduction by malesis hypothesizedto be importantto successfulmating in cod Brawn 1961a,b; Engenand Folstad 1999; Hutchings et a/. 1999!and we wantedto examinepatterns of variation in the sizeof their sound-producing "drumming" musclesin more detail. Brawn 961b! found thatAtlantic cod produced sound most frequently during the spawning period and although both sexeswere capable of producingsounds throughout the year,only malesseemed to do so during the spawningseason, typically during aggressivedefense of territoriesand courtshipdisplay.

Proceedingsfrom the /nternationa/ Workshop on the App/ications of PassiveAcoustics to Fisheries 92 During March 2001 February20G2, we sampled approximately 1GGcod/month from NAFODivision 4Xto quantifyseasonal and individual variation in body conditionand drumming muscle mass, We found that drurnrningmuscle mass tended to increasewith fish size,Furthermore, when we con- trolledfor fishsize, we found that spawning males had larger drurnrning muscles than non-spawning males Figure 2! butthere was no such relationship for females.In addition,males had larger drummingmuscles than females both duringspawning and non-spawningseasons.

Interestingly,we also observed a weak,but significantrelationship between drumming muscle somaticindex and bodycondition for malesin spawningcondition Figure3!. Thissuggests that maledrumming ability could convey reliable information to femalesabout mate quality.

Conclusions Wewill continueour research on Atlanticcod by combining pedigree data with phenotypicand behaviouralobservations of fish in our aquariumto assesscorrelates of reproductivesuccess, Also, we will studysound production by codin moredetail by examiningthe typesand characteristicsof soundsproduced, the behaviourafcontexts in which soundsoccur, and temporalpatterns of sound production.

In recent years,stock collapseshave causedmany Atlantic cod fisheriesto be reduced and others evenclosed, Knowledge of Atlanticcod spawningbehaviour will likelycontribute to betterunder- standingof populationdynamics and improved ability to predictthe effects of fishingon codpopu- lations.

Acknowiedgernents Thanksto JimEddington, Paty Avendano, and the Fishermenand Scientists Research Society for technicalassistance. Financial support for this researchwas provided by a NaturalSciences and EngineeringResearch Council grant and a Petro-CanadaYoung Innovator award to JAH.

References Brander,K. 1994,Spawning and life history information for NorthAtlantic cod stocks. ICES Coop, Res.Rep. No. 205.

Brawn,V.M, 1961a. Reproductivebehaviour of the cod Gaduscallarias L.!. Behaviour 18; 177-198.

Brawn,V.M. 1961b. Sound production by the cod Gaduscallarias L.!. Behaviour 18: 239-255.

Chambers,R C.,and K GWaiwood. 1996. Maternal and seasonal differences in eggsizes and spawning characteristicsof captiveAtlantic cod, Gadus morhua. Can, J, Fish. Aquat. Sci. 53; 1986-2003.

Proceedingsfrom the Internationa! Workshopon the Applications of PassiveAcoustics to Fisheries 93 Engen,F., and I. Folstad, 1999. Cod courtship song: a song at the expense of dance? Can.J.Zool. 77: 542-550.

Hutchings,J.A., T.D. Bishop, and C.R.McGregor-Shaw. 1999. Spawning behaviour of Atlanticcod, Gadusmorhua: evidence of matecompetition and matechoice in a broadcastspawner. Can.J. Fish. Aquat. Sci, 56; 97-104.

Kjesbu,O.S., P. Solemdal, P. Bratland, and M.Form. 1996. Variation in annualegg productionin individual captive Atlantic cod Gadusmorhua!. Can.J.Fish. Aquat. Sci.53: 610-620.

Ivlorgan, MJ., E.M. DeBlois, and G,A,Rose, 1997. An observation on the reaction of Atlantic cod Gadusmorhua! in a spawningshoal to bottomtrawling. Can.J.Fish. Aquat, Sci, 54: 217-223.

Myers,R.A,, G, Mertz, and S.Fowlow. 1997. The rnaximurn population growth ratesand recovery times of Atlantic cod Gadus morhua!. Fish. Bull. U.S.95: 762-772.

Nordeide,J.T., and I.Folstad, 2000. Is cod lekkingor a promiscuousgroup spawner?Fish and Fisheries 1: 90:93.

Rose,G.A. 1993. Cod spawning on a migration highway in the north-west Atlantic. Nature 366:458- 461,

ScottWB., and MG.Scott. 1988.Atlantic Fishes of Canada.Can. Bull. Fish. Aquat. Sci. 219, 731 pp.

Srnedbol,R.K., and J.S.Wroblewski. 1997. Evidence for inshorespawning of northernAtlantic cod Gadusmorhua! in Trinity Bay,Newfoundland, 1991-1993. Can.J. Fish, Aquat. Sci.54: 177-186.

Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 94 Illustrationsand Diagrams

3,5

3,0

2.5

2.0

Q 1.5

1.0

0.5 0.0 FemaleFemale Male Male 4T 4X 4T 4X Figure1. Drumming muscle somatic index DMSI!for femaleand male Atlantic cod from North west Atlantic Fishery Orgonization NAFO!Divisions 4T and 4X. Boxplots indicate outli ers points! and 10th,25th, 50th,75th, and 90th percentiles. Sample sizes given oboveestimates.

3,5 3.0

1.0 05

0,0 Female Female Male Male Non-spawningSpawning Non~wningSpawning

Figure2.Drumming muscle somaticindex DMS for! non-spawning and spawning female and male Atlantic cod fromNorthwest Atlantic Fishery Organization NAFO! Division 4X. Box plots indicate outliers points!and 10th,25th, 50th,75th, and 90thpercentiles. Sample sizes given above estimates.

3.0

2.5

V3 2.0 CI15

1.0

0.5 0.900,95 n00 1.05 1.10 1.15 130 1.25 130 pnlton'5 K

Figure3, Therelationship between drumming muscle somaticindex DMSI! and body condition asindicated by Fulton'sK conditionfactor! for spawningmale Atlantic cod from Northwest Atlantic Fishery Organization NAFO! Division 4X.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 95 Proceedingsfrom the internationalWorkshop on theApplications of PassiveAcoustics to Fisheries 96 Section 2

Technology, Future Development and Applications

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 97 Proceedingsfrom the internationalWorkshop on theApplications of PassiveAcoustics to Fisheries 98 ~ Spotted Seatrout Spawning Requirements and Essential Fish Habitat: A MicrohabitatApproach Using Hydrophones

Donald M. Baltz

Oceanographyand CoastalSciences, Coastal Fisheries Institute, LouisianaState University,Baton Rouge, LA 70803, USA.

Summary Hyrdrophonescan be usedin conjunctionwith a rnicrohabitatapproach to yielda fish'seye view of its habitatrequirements. At the finestscale, the rnicrohabitatof an individualis the site it occupies at a given point in time, Sitesare presumablyselected to optimize an individual'snet energy gain while avoiding predators i.e.,tradeoffs of growth vs mortality!. Sincesimilarly sizedindividuals of a speciesselect similar microhabitats, many careful measurements of individualsand associated physical,chemical, and biological variables should define the population's responsesto environmental gradients. As defined here,the microhabitat is an occupied site,not a little bitty habitat type, Fine- scalemeasurements of environmentalconditions at a siteoccupied by oneor moreindividuals con- stitutean observation,and manyindependent observations characterize the population'sresponse to complex gradients.

Habitatis a looselyused ecological term that canbe appliedat the individual,population,and corn- rnunitylevels and is often entangledwith so manyother ecological concepts that it canmean everythingand thereforenothing. The term 'habitat'has almost been relegated to the statusof a pseudocognate sensuSalt 1979,Ecology! in that it is a term in common use and each individual who uses it feels that all others share his own intuitive definition. Nevertheless, it is used and can be useful.We can usehabitat as the rangeof environmentalconditions in whicha species/population/life-history stage can live. It is a generalterm that broadly defines where a specieslives without specifyingpatterns of resourceuse sensuHurlbert 1981, realized niche = resourcesused: energy, materials,and sites EvolutionaryTheory 5:177-184!!.There are severalpoints of view. Froma fish's point of view,its distributionover environmental gradients describes its habitat.From a biologist's point of view,strata in the environmentcan be arbitrarilydescribed as habitats, but moreproperly as"habitat types". At the cornrnunitylevel, the environmentsdominated by a singlespecies e.g., Spartinaalterniflora! may be characterizedas Spartina habitat, but moreproperly as a "Spartina community".

Theconcept of EssentialFish Habitat EFH!is basedon 1996federal legislation and is aimedat enhancingthe sustainabilityof our fisheries.The legislation established four levelsof dataquality in

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 99 defining EFH:I. Presence/absence,II. Density patterns e.g.,population responses to gradients,suit- abiiity!, III. Condition/health e.g.,growth, parasite loads,pollution loads,RNA/DNA ratios!, and IV. Production e.g.,secondary production, reproductive output!, Whatis EFH?Essential is a qualifier that carries a notion of quality. We are notjust asking where a specieslives Level l!,but where it liveswell LevelsII-IV!. Where are its resourceneeds best met? Nowwe areconcerned with patterns of resourceuse sensuHurlbert 1981, realized niche = resourcesused: energy, materiais, and sites Evolutionary Theory 5:177-184!!.

How can we use a fish'seye view to define EFH?We can seekanswers to three questions. How are speciesand life historystages distributed in the environment?What intervals along environmental gradientsare selectedor avoided?What is mostimportant to the fish in termsof growthand/or survival?

LevelI data:Presence/Absence data: Mostrisk averse approach to protectinghabitat basedon the precautionary principle!; however,reliance on Level I data overprotects lessvaluable habitat and essentiallyequates water with EFH,High quality habitatis giventhe samelevel of protectionas Low quality habitat and scientists/managerslose credibility.

LevelII data:Density data:. Uses fish population'sresponses density patterns! to environmentalgra- dients. LevelII assessmentscan be improvedby relatingpopulation's response in termsof resource useto resourceavailability e.g., habitat suitability!, and high qualitycan be distinguishedfrom low quality habitat. HabitatSuitability [S = Suitability= P E F!/ P E!]is an indexof habitatquality based on a quotient of ResourceUse and ResourceAvailability Bovee,K.D. & T.Cochnauer, 1977, U,S.Fish & WildlifeService Biological Services Program FWS/OBS-77/63!. Resource use is a probability statement,given the presenceof fish,and resourceavailability is a probabilitystatement, regard- lessof the presenceof fish. Suitabilityis an indexof usedivided by availabilitythat rangesfrom zero intolerable! to one optimal! after standardization,

LevelIII data:Growth data: I havenot beenable to relatethis levelto hydrophonework on spotted seatrout, but others may find an application for other soniferousspecies that make soundsfor non- reproductivefunctions e.g.,foraging parrotfishes!. What environmental conditions foster growth of earlyjuvenile spottedseatrout? Nursery microhabitat selection is presumablycontrolled by some combinationof physiologicalconstraints, prey distributions, foraging success, competitor densities, and predationpressure, all of which mayinfluence growth and/or survival. Linkages between rnicrohabitat,diet, & conspecificdensity may predict recent daily growth which in turn revealsthe recruitment potential of preferred nursery characteristics Baltzet al,1998,Env Biol Fish53: 89-103!.

LevelII/Production data: Thisis the bestkind of informationand the bestexample is from a studyof oysterseed production Chatry,Dugas, and Easley1983, Cont. Mar. Sci. 26: 81-94!. Oyster seed set and growth are bestat 20-22ppt LevelIII data!,but oysterpredators drills, etc! seriouslydeplete populationsin high salinitywater > 15 ppt!. Oysterseed production is highestfor seedset at 12-16 ppt the previoussummer, and thereforeEFH for oysterseed production is highestin a narrowsum- mer salinity range of 12-16ppt.

Proceedingsfmrn the International Workshopon the Applications of PassiveAcous'ties to Fisheries 100 I will argue that suitability indicesfor reproduction Saucier5 Baltz,1993,Env Biol Fish36: 257-272! arehigh-level EFH data and qualifyat LevelIV. Moreover,this kindof datacan be acquiredeasily with hydrophones.Saucier and Baltz993! useda microhabitatapproach to identifyselected and avoidedpoints along salinity,depth, substrate, and velocitygradients used for spawningby spotted seatrout.Relatively deep, moving waters with a salinityof 14-23and a temperatureof 29-33'C were selected.Conflicting literature from earlierstudies in the northernGulf of Mexicosuggested that spawningoccurred more or lessexclusively in bays,passes or the opengulf. Wefound that spotted seatroutspawn across a widevariety of habitattypes bays,channels, passes, and opengulf! where environmentalconditions are right. Wefound that spawninglocations shifted along a salinitygradi- ent up to 30 km on a north-south axis, and concluded that environmental conditions were more important than places,

Spawningtemperatures for Louisianaspotted seatrout Spawning salinity for Louisiana spotted seatrout Thereare several pitfalls to avoid.Non-linear effects along environmental gradients should be expected.Non-representativeness in sampling design may lead to biasedresults, especially sarn- pling biasthat focuseson particularhabitat types may generate misinformation, Noisy crews, boats and trafficmay makeit difficultto locatespawning aggregations. Misidentification of drumming speciescan be avoidedby carefulcomparisons with knownrecordings, and verification of actual spawningby the collectionand rearingof eggsfrom drummngsites to identifiablelarvae is important. A stratifiedwater column may present contrasting environmental variables in a verticalprofile We want to know what's going on at the fish's nose!.

HydrophoneTechniques 8 Assumptions: Aggregation size: Sound Intensity may be usedto estimate SourceLevel SL!if distanceto sourceis known. SourceLevel is calculatedby addinga one-way sphericalspreading loss i.ea 20 log [depth in meters- 1]!for a correction absorption is ignored!, It is a continuousvariable that estimatesgroup sizefor statisticalmodeling: SL = microhabitatvari- ables+temporal variables+ e. A recordedSound Intensity my standardsettings were 132 db re 1 Ii pascal!of +5 db yieldsa SourceLevel of 139.6db for an aggregationon the bottom in 15 m of water[e.g., 132+ 5+ 0 log 14!= 139.6db]. A cylindricalcorrection or no correctionmay be more appropriate under given circumstances.

FutureApplications: My wish list is topped by a fixedor moveablelistening array with overlapping directionalcapabilities to generateposition fixes, computer programs to processfix data,and realtime transmissioncapabilities to allowa smallboat to moveto aggregationsites and random sites for measurementsof resourceuse and availability.

Recommendationsfor EFH:Quality research and wise managementrelated to fish habitatdepend on how clearlywe candefine habitat and EFkand that we areall discussingthe sameconcepts. We shouldtry to take a fish'spoint of view and let them describewhat isessential along environmental gradients.By comparing resource use with environmentalavailability, we gain insightsinto patterns

Proceedingsfrom the International Workshop on the Applicatians of PassiveAcoustics to Fisheries 101 of selection and avoidance. We can identify biological endpoints that reflect the health and well beingof individualsand communitiesof fishes.Use of the bestdata and researchdesigns available will help avoid management errors in describing EFH.Management errorsthat result in over- or under-protecting EFHcan be viewed as having positive and negative outcomes:

Over-protection Under-protection

Species & habitats are better protected +! Species& habitats at greater risk -!

Scientists& managersmay lose credibility -! Scientists& managersmay lose credibility -!

Costs the regulated group its profits -! Regulated group is happy +!

Enforcementis more expensive -! Enforcement is lesscostly +!

Cieariy,we can usehydrophones and a microhabitatapproach to crediblydescribe EFH for some soniferousspawning fishes,like spotted seatrout.

Acknowledgments I amgrateful to Grant Gilrnore and Mike Mok for an acoustical primer and other assistance,Scott Holtfor showingus how to rearlarvae, Louisiana Sea Grant for funding,and RodneyRountree, Tony Hawkins,& Cliff Goudey for putting together the workshop.

Proceedingsfrom the international WorAshopon the Applications of PassiveAcoustics to Fisheries 102 ~Creating ~ a Web-based Library ofUnderwater Bioiogital Sounds

JackW. Bradbury and Caroi A. Bloomgarden

MacaulayLibrary of NaturalSounds, Cornell Laboratory of Ornithology 159Sapsucker Woods Road, Ithaca, N.Y. 14850, macaulaylibraryOcornell.edu

Introduction Establishinganarchive of fishand other underwater biological sounds will meetmany of thelong- standingchallenges faced by marineacousticians - the ability to cataloguetheir soundsand data in a waythat fosterscomparative studies, easy access to the soundsfor analysisand identification, and thecapacity to searchthrough passive recordings for soundsof particularinterest. The Macaulay Libraryof NaturalSounds MLNS!, with a longhistory of workingtoward these goals in ornithology and animal behavior,recently launched a new Internet-accessiblearchive of underwater sounds with the help of over sixty individual recordistsand institutions worldwide. Researcherswill be able to annotatetheir soundswith detailedand extensive data through an onlinedatabase application, summarizesearch results in exportabletables and maps,and downloadcopies of recordingsfor research,teaching, and conservation. MLNS is cornrnittedto dual goalsof maintainingopen access to allowother researchers to listen and help identify sounds, while protecting recordists'copyrights and restrictingaccess during the publicationprocess. Detailed and extensivemetadata are needed, however,to create the functionality such an archive requires.

Acquisition of Source Material A recentsurvey of suitableoriginal recordingsresulted in commitmentsby morethan 60 researchersor institutionsto supplyoriginal tapes and rnetadatafor archivalat MLNS.These consist of over8000 hours of audiotape and 800 hours of videoand include recordings of 95species of marinemammals and morethan 200 speciesof fish representing36 families!and marine invertebrates.Upon request, MLNS staff will visitparticipating institutions to helporganize and pack origi- naltapes, collect the metadataand any information required to importit, and then carefully track the statusand location of all contributedmaterial through the shippingand archival processes,

Restoration Manyolder recordings exist on deterioratingtape stocks. These must be treated before copying. MLNShas extensive experience and an excellenttrack record in tape restoration.Many of these tapescan be restoredin-house using controlled baking and vacuumtreatments. A fewmay be so

Proceedingsfrom the InternationalWorkshop on theRpplications of Passivekcoustics to Fisheries 103 deteriorated that they must be out-sourced to specialistswho examine the molecular structure with electron microscopesbefore undertaking situation-specific restoration procedures.

Ingestion Most analog sound tapes are digitized once at high resolution 96 kHz/24 bits!. Although the high samplingand bit ratesare not necessaryfor all recordings given ambient noise levels and frequency compositionof the sounds!,these high-resolution settings greatly accelerate the archivalprocess by freeingtechnicians from detailedmonitoring of signallevels and inadvertentaliasing. They also preserveany high frequencysounds that are unnoticedor in the backgroundbut that maylater prove of interest. Properdigitization of Odontocete sonar signalswill require a combination of replay at reduced speedsand even higher digitization rates.Digital recordings are copied at their original rates. Analog video will be converted to digital tape replicas.All digitized materialswill be stored on iocal hard disks until transferred to hard media,

Extraction Whereasterrestrialrecordists can limit recordingtime by watchingtheir subjects,marine researchersoften recordblindly for long periods,and their recordingstherefore often havea much smaller fraction of useful content than do terrestrial ones. At least a third of the contributed audio material consistsof such unedited continuous recordings.Once digitized, these must be examined in real-timeand the relevantsounds extracted. We will workwith developersto adaptprototype detector software for real-time extraction of appropriate marine sound tapes. This tool will be essentialfor reducing raw audio streamsto separate sound files.

Formatting & Storage All high-resolutiondigital copies of extractedsounds and videoswill be preservedin a deeparchive. Soundswill be storedas AIFF files on DVD-ROMdiscs in a computer-controlledjukebox array. Video will be encodedas MPEG-2 files and storedin a near-linedigital AIT AdvancedlntelligentTape! library.Copies of eachsound and video will be created in a variety of down-sampled popular for- mats compact disc quality, RealAudio,QuickTime, Windows Media,and perhaps MP3! and stored on CLO'snew EMCSymmetrix hard drive system.These latter copies will be the ones availableover the Web.High-resolution copies can be obtainedby specialorder, Automatic routines will randomly monitorthe integrityof the DVD-ROMcopies and the EMCsystem copies. Damaged files can be robotically regeneratedfrom backup high-resolution copies.

Identification and Annotation Remoteexperts will be ableto examinecopies of extractedsounds or annotatecopies of longer

Proceedingsfrom the international Workshop on the Appiications of PassiveAcoustics to Fisheries 104 behavioralsequences both audio and video!. Given our ability to createa lowerresolution copy of anysound or videoclip, it will beeasy to downloadthese to theconsultant over the Web along with softwarefor recordingidentifications or annotationsthat would then be uploadedto our database. Oursoftware will bespecifically designed to acceptannotation data created remotely and synchro- nizeit with all subsequentcopies of thefiles. These tools willthus create a muchlarger pool of participating consultants.

Importing of Metadata CLOhas adopted one of theindustry standards for itsdatabase, Oracle's relational system, and is designinga dataarchitecture that conforms with the DublinCore http: //www.dublincore.org! protocols. Thesedefine a setof rnetadataand XML tags that allow our databasesto be accessibleand compatible with other librariesand rnuseumsworldwide, Lower levels in this architecture allow for taxon-specificdata for behavioralrepertoires or habitatuse, sophisticated GIS links using ESRI routines,complex and high leveldata mining protocols, and within-file e.g.annotation and extracted parametricdata! searches. CLO is developing general tools for dataimportation and searching througha widevariety of databaseformats, All data,whether entered by handor ported,will be checkedfor accuracyand veracity before being published online.

Client Services CLO'ssound and video libraries have a widediversity of users.These include private individuals, sci- entificresearchers, conservationists, wildlife managers, education programs at all levels,website owners,military and government agencies, the mediaand film industries,and variouscommercial companies.Our major goal in the recentacquisition of an EMCenterprise storage and Web delivery systemwas the provisionof rapid,direct, and reliable access to theCLO archives through the Internet.This requires JAVA and MTML/XML programs for theWeb pages and underlying engines for a vaiiety of online servicesincluding a! powerful searchesof our metadata and within-file annota- tions;b! provisionof searchresults as data tables with hot linksor mapsincluding links to a variety of onlineGIS tools; c! theability to hearany selected cut online;d! theability to collecta seriesof multimediaselections onto a worktablefor comparison,sequencing, or editing; e! creationof a shoppingcart with secure credit-card payment protocols; and f! trackeddelivery of requested resourcesthrough streaming, Web downloads, or shipmentof hardcopies CD,DVD!. Some of these featuresare being developed CLO-wide, but others will requirespecific adaptations for the marine animal sound collections.

Analytical Tools ln additionto search,selection, and retrieval, CLO intends to providevarious sound analysis tools online.These may include the abilitiesto a! seea playablespectrogram or waveform or both time-

Proceedingsfrom the InternationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 105 aligned!of anysound in the archive;b! selectand playany part of a visiblespectrogram or waveform; c! selecta large number of soundsin the archive and submit a batch job to compare each sound with every other sound using any of severalalternative tools spectrographic cross-correlation, temporal cross-correlation, multiple measurement and PCA, etc.!; and d! submit an unknown sound and associatedrnetadata and receivea likely identification or list of alternative suspects!,

Acknowledgements Fundingfor the MarineAnimal Sounds Archive is throughthe U.S.Office of NavalResearch. Many thanksto BobGisiner at ONRfor his encouragementand support on this project.

Proceedingsfrom the Internationa/ IrVorkshopon the Appiicatioris of PassiveAcoustics to Fisheries 106 '~ Potential~ for coupling ~ of underwaterTV monitoring with passiveacoustics

Charles A. Barans', David Schmidt', Myra C. Brouwer'

', ' Marine ResourcesResearch Institute, South CarolinaDepartment of Natural Resources,2'I 7 Ft. Johnson Rd,,Charleston, SC 29412 ' [email protected] 'brouwermornrd,dnr state.sc.us

'Jackson and Tull - SMARTech Division, 1211 Ben Barron Lane, Moncks Corner, South Carolina 29462 [email protected]

Introduction The temporally and spatially fluid nature of fish associationsoften confuses interpretations of their underwatersounds. Ideally, visual confirmation of the soundproducers and any behaviorsassociat- ed with soundmaking should accompany acoustic data. Investigators have long beenexpanding their inventory of specific sounds that represent,conclusively or potentially, specific underwater sources. These are the acoustic "standards" by which to compare unknown sounds for recognition/identification purposes.Unfortunately, these standardsare often not availablefor acoustic researchon fishes.Although some sonic signatureshave been corroborated with visual observations,many more are needed to assistin interpretationsof sonicdata from hydrophones placed in complex habitats with many interacting speciesof vertebrates and invertebrates.The underwater television UWTV! is ideal for direct correlations between specific sounds and their causes,if the water visibility is acceptable.

Underwatervideo devicescan provide a wealth of information to scientists and fishery managers including seasonalrnovernents of fishes,the potential for development of indices of abundance for some migrating and resident populations,and any seasonalbehaviors associated with the forma- tion of pre-spawningaggregations along a migration route. An UWTVsystem offshore allows the study of fisheson the bottom throughout the year without the costly trips to a researchsite in inclement weather.The present visual capability of UWTVshould be integrated with acoustic information to enhancefisheries biologists'understanding of fish behavior and movements within the region.This paper describesrecent resultsfrom a permanent installation of an UWTVat an artificial reef offshore.

The UnderwaterTelevision System Theresearch site was established in 25-28m ofwater about 72 Krnoff centralGeorgia on May 11, 1999with the deploymentof severallarge fish attraction units ArtificialReefs, Inc.!. On August 24, 1999,the underwaterTV cameras, cable and computer were installed and imageswere transmitted

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 107 via microwavesto shore.Artificial reef structuresare arranged in a circlearound the camerasystem to maintain a residentaggregation of reef fishes,to attract transient speciesand to focus local fish activities within the view of the cameras,

Thevideo systemconsists of two main parts,A pressurehousing, located on the seafloor and a video capture engine,located remotely.Six monochromevideo camerasare housed with a rnicro- controllerand a fewbasic sensors. The micro-controllerprovides the meansto multiplexthe 6 analog video signalsto onecoaxial cable running between the pressurehousing and the videocapture engine.The video capture engine is a computerrunning under the WindowsNT operating system. A consoleapplication controls a videoframe grabber, which takes the analogvideo signaland con- vertsit to digital images.The system has the abilityto capturemulti-frame or singleframe images basedon parametersset by the user,The micro-controller in the pressurehousing receives corn- mandsfrom the videocapture engine for cameraselection, tilting data,and systemstatus updating. Theembedded computer also acts as a webserver through which the videosystem is controlled. File transfer and systemparameter updates are made possible by an interface between the web server and the consoleapplication controlling the video system using pcANYWMERE.

Small black and white security cameras SupercircuitsPC-23C! with low light capabilities to 0.04 lux! and relativelylow resolution60 lines!were used. Camera lenses of 8 mmallowed a 12degree angleof view,and the seabedwas in view at about 13.7m fromthe camera.Daily observations -65! wereconducted between 1200 and 2130GMT GreenwichMean Time!. Still images-15 Kb jpg! were recorded and logged at 10 minute intervalsfor 10 sec,Video clips -400 Kb avi! were recorded on the hour from camera No. 5, since only cameraNo. 5 wasdirected at reef structure with any reeffish activity.Images were downloaded from the remotecomputer to the laboratorycorn- puter for fish counts and long-term data storage.

Observationsusing UWTV We havelearned how to deployand maintainthe UWTVsystem and remoteoperations systems. We havetemporally documented species presence and activity. The seasonal dates of the first appear- anceof variousfish speciesare especially important for identificationof any prespawningmigration to the southby adultgrouper, one of our maintarget species. Seasonal changes in the makeupof the fish assemblageat the UWTVsite appearmuch greater than previouslybelieved. We are documenting the annual cycle of juvenile recruitment in spring and summer followed by intense predation by transient specieslater in the year,

Largeschools of baitfish havebeen present in mostseasons accompanied by schoolsof predatory greateramberjacks Serio/a dumerili!.The subjects of interestto us,snapper and grouperspecies, however,have yet to establishresident populations at the site.Year-round resident species included Atlanticspadefish Chaetodipetus faber!, gray triggerfish Baiistescapriscus!, and the predatorsblack seabass Centropristisstriata!,and great barracuda Shyraena barracuda!.Other resident species may

Proceedingsfrom the /nternationa/ Mforkshopon the Applications of PassiveAcoustics to Fisheries 108 not havebeen observed due to decreasedvisibility and/or increased cryptic behavior during winter.

The visibility near the bottom was relatively poor throughout May,at some times in late summer and often after winter Northeasterstorms and hurricanes.Swarms of juvenile round scad Oecapteruspunctatus! appeared in rnid-May and were occasionallyaccompanied by snapper and grouperspecies. Transient species in Mayincluded loggerhead seaturtle Caretta caretta!, sand tiger shark Odontaspistaurus!, rock hind Epinephelus adscensionis!, nurse shark Ginglymostomacirra- tum!,and cobia Rachycentrumcanadum!. The settlement and recruitment to an areaby juvenile baitfishmay attract many temporary predatory species. In 2000,we first sightedsmall baitfish in April, although periodic clouds of very small juveniles could not be identified to species.

During 1999,tomtate Haemulonaruolineatum!, especially juveniles, were one of the most abundant and conspicuousrnernbers of the fish assemblagein closeproximity with the structuralreef units. Largeschools of roundscad often swamin and out of view nearthe tops of reefunits. Immediately aboveany fish structureand well up into the watercolumn were loose aggregations of adult greateramberjack, Other jacks occasionally passed through the site,including biack bar jack Caranx ruber!.

Although residentpredators must significantly reduce recruitment of manyspecies, large stochastic predationevents appear to havea formidableinfluence on mortalityand survivalof smalland juvenile reef fishes.Two important large-scalepredation events observed in 1999-2000were the arrival of migratingloons Caranxruber! and the rnid-winterappearance of largepopulations of ctenophores believed to be Leucothea milticornus! near the bottom. We observed the loons to visu- ally selectfish preyin and nearthe structuralreef units within a meterof the bottom.Also, the large numbersof ctenophoresand/or jellyfish in winter correspondedto the temporaryresidence of an oceansunfish Mo/amola! and a relativelylarge population of adult Atlanticspadefish. Both species are knownto feedon jellyfish.The importance of predator-preyrelationships was confirmed by inference from general observationsof the relatively simultaneousarrival of baitfish and some of the higherlevel predators in the earlyspring. The infrequent appearance of high levelpiscivores at the smailartificial reef site suggests large feeding ranges of manyspecies, which appear to be"pass- ing through" looking for feeding opportunities. Speciesthat may move back and forth between other habitatswithin their huntingrange and wereobserved at the site includelarge adults of log- gerheadturtles, sand bar sharks, red snapper Luj anus campechanus!, gag Mycteropercamicrolepis! and scamp M. phenax!,

Discussion Observationsfrom the artificialreef research site can contribute significantly to the understanding of the short-termand long-termtemporal changes in an offshorereef fish assemblage.Permanent installations of UWTVsystems have the advantage of non-obtrusiveobservations of fish interactions.The sortsof behaviorsthat areof mostinterest to biologists,such as feeding or spawning,are rarelyobserved in the wild.Documenting such rare events often requiresconstant, long-term obser-

Proceedingsfrom the international Workshop on the App/ications of PassiveAcoustics to Fisheries 109 vationthat is difficult undernatural conditions because the oceanis always changing, Observations by diversare severelylimited duringseasons of high seas,often includingboth winterand spring, whenmigration and/or spawningactivities among reef fishes most often occur.

Althoughthe lackof mobilityof our UWTVis a spatiallimitation, a semi-permanentsetting allows temporalinvestigations. Similar visual studies could develop sound catalogs of transientspecies and moredetailed behavior-related sound patterns of residentspecies for potentialmanagement applications.For instance, estimates of populationsize of coral-nibblingparrot fish might be madeafter correlations between the mean rate of munching done per fish, with visual verification of the feeding behavior/sound relationship.

Synergistic information would come from the simultaneous combination of visual and sonic infor- rnation.The addition of lessexpensive, passive acoustic data gathering devices could compensate for the lackof spatialcoverage by moreexpensive UWTV systems. It couldalso provide more com- pletecoverage of the eventstaking place in the vicinityof the cameras,but beyondtheir field of view.

Imagine,if you will, the interestingarray of soundsthat mighthave accompanied the feeding of loonson cigarminnows near the bottom,Atlantic spadefish biting a chunkoff a passingjellyfish or a schoolof tuna passingthrough the artificialreef structures. Each of thesecomplex sound series maybe far more interpretablewith TVdocumentation during the first severalencounters, Behavioral observations correlated with acoustics and environmental conditions and validated over time would contributeto the interpretationsof resultsfrom othersampling areas for whichonly acoustic data are available.

Integrationof a relativelypermanent TV and passivehydrophone offshore to refinethe acoustic "dictionary"seems to be nearingreality. The UWTV systems exist associated with FishWatch, Africarn,Aquarius and specific public aquariums throughout the US.The bandwidth necessary to add simultaneouspassive acoustic data should be minimaland be waitingonly forthe enthusiasm to make it happen.

Theprimary scientific objective of the UWTVsystem established off Georgiawas to documentand quantifyprespawning aggregations of gag grouperas they movesouth along the continentalshelf. lf an associatedsound recognitionpattern were associated with suchfish aggregations and movements,multiple listeningstations could be establishedat keylocations across the shelfand along the potentialmigration path at a costfor monitoringmuch less than that usingother methods.The visualfindings of the presentUWTV study expand our understandingof the importanceof large scalestochastic predation events on relativelylocalized reef fish aggregations, especially of juveniles and bait species.The soundsgenerated by the assemblageinteractions would havetilled chapters of a catalogon reeffish sounds, The scientific cornrnunity anxiously awaits the developmentand application of tools that will allow simultaneousvisual and sonic investigationsof fish associations and behaviors.

Proceedingsfrom the International III/orkshopon the Applications of PassiveAcoustics to Fisheries 110 Acknowledgments Any marine researchrequires a team effort with many experts and professionalsinvolved to accom- plisheven a smalltask offshore. In thecase of remotetransmissions from an underwater TV system, the numbersof supportelectronics/computer, divers, vessel operators and agencies willing to loan facilitiesand/or manpower to getthe job donecan be staggering, We thank all those multi-agency staffand, in particular,the staffthat always can be depended on to accomplishmultiple tasks to keepthe system functioning: Trent Moore, Cheryl Burden Ross and Travis McKissick. We thank many staffof thefollowing institutions/ agencies/ groups for theirundying support, including: the SkidawayInstitute of Oceanography,the Gray'sReef National Marine Sanctuary, the SCMarine ResourcesDiv, Artificial Reef Section and MARMAPprogram, the GeorgiaCoastal Resources Division andthe USNExplosive Ordnance Disposal Mobile Unit ¹12. We are grateful for funding from the US Navythrough the Office of NavalResearch, National Oceanographic Partnership Program, Grant No, N00014-98-1-0808.

Proceedingsfrom the International 5'orkshop on the Applications of PassiveAcoustics to Fisheries 111 ~ ~ ~ ~ Application of PassiveAcoustic Methods for Detection, Locationand Tracking of Whales

Christopher W. Clark

BioacousticsResearch Program, Cornell Lab of Ornithology, 159 SapsuckerWoods Rd,,Ithaca, NY 14850cwc2Ocornell .edu, http:IIwww.birds. cornell.edu/brp/

Introduction Baleenwhales produce species specific sounds, At leastfive speciesproduce long, patterned, hierar- chicallyorganized sequences of soundsreferred to assongs. Baleen whale distribution and relative abundanceestimates are traditionally based on visualsurveys from vesselsand/or airplanes. This approachis limited by visibilityconditions and accessto observationplatforms. Acoustic monitoring usingeither singleor multiplesensors offers a significantirnprovernent by increasingspatial and temporal sampling.Throughout the last 20 years,acoustic hardware and software tools have been developedand appliedto surveywhale species and gaininsights into naturalbehaviors, This includesthe useof NavySOSUS arrays to detect andestimate numbers of vocalanimals throughout an ocean basin,autonomous seafloor sensorsto detect, locate and track speciesof interest in regions,and sparseor towed hydrophonearrays to detect,locate and track selected species in spe- cificstudy areas.For at leastfour species,SOSUS data reveal annual seasonal and largegeographic fluctuationsreflecting migration, feeding and breedingpatterns. For bowheads combined visual- acousticefforts have lead to calculationof a robustpopulation assessment and trend over a 20-year period,as well asunderstandings of acousticfunctions. For blue and fin whales,integrated approachescombining passive acoustic methods with visual,biopsy, photo-ID and preyfield sur- veysare beginningto revealcritical details of behavioralecology and significant insights into vocal functions.

Background TheCornell Bioacoustics Research Program specializes in the developmentand applicationof advancedtechniques to investigatethe mechanismsand evolutionary bases of animalacoustic behaviors.Techniques successfully developed for the studyof one organismor taxonomicgroup are often appliedto anothergroup. Part of the motivationfor includingthe topic of whalesin this sym- posiumwas to providean opportunityto exchangeinformation with researchersprimarily interested in fishes.Clearly many of the tools developedfor studieson whalesare applicable to fish.Species in both taxa producerich assortmentsof soundsin the low-frequencyband <1000Hzj. Most sounds are speciesspecific and can be used as indicatorsof speciespresence and relative abun-

Proceedingsfrom the international IIIIorkshopon the Appiications of PassiveAcoustics to Fisheries 112 dance.Males are knownto produceacoustic displays associated with breeding.Similar sound prop- agationmodels can be appliedto quantifyprobabilities of detection,An integratedapproach in whichacoustic techniques are combined with other methods e.g.,visual, molecular, oceanographic! canyield tremendousadvancements in our collectiveunderstandings of marinebiology.

Whale bioacoustics All 11species of baleenwhales produce sounds, Representations of soundrepertoires are complete forthe five coastal species, bowhead, gray, humpback and the southern and northern right whales. There are good representationsfor two pelagic species,blue and fin whales.Whale sourcelevels RMSpower in dB re 1pPaCi 1 m!have been reported as high as 188dB tabulatedin Richardsonet al.1995!. Under certain conditions e.g.,water depth that is not well matchedto the signal'sfrequen- cy bandof lowesttransmission loss, or highly reverberantenvironments!, there is little or no advan- tageto increasedsource level, and selectionshould favor changes in otheracoustic features to optimize communication effectivenessand range.

In the marineenvironment, assuming a selectiveadvantage for tong-rangecommunication, the influencesof physicalacoustics should have imposed strong selective pressures on the acousticfea- turesof communicationsounds. There is evidencein supportof this generalhypothesis on sound functionwhen consideringthe physicalacoustic properties of the oceanenvironment in combination with the acousticfeatures of soundsproduced by mysticetewhales. Two primaryacoustic prop- ertiesthat stronglyinfluence cornrnunication range are transmission loss TL!and ambientnoise. In a shallowwater habitat < 200-300rn! soundsin the 100-800Hz band experience the lowestTL and thereis often a windowof low ambientnoise in this frequencyrange. Along a shelfbreak or in deep ocean environments > 1000 rn!, sounds below 100 Hz experiencethe lowest TL and between 10-50Hz there is a plateauof low ambientnoise. The acoustic features for specieswhich breed and foragein predominantlycoastal habitats are very different from those from a pelagicenvironment, as illustrated in Figure 1.

Ambientnoise levels are different for thesetwo environments,and the dominantfrequency band of a species'songis generallymatched to the frequencyband of low ambientnoise as shown in Figure 2 Clarkand Ellison,in press!.

Traditionalvisual survey methods are inadequate for documentingspecies presence/absence, distri- butionor relativeabundance. The spatial and temporalsampling scales required are prohibitive for shipor aerialsurveys, but passiveacoustic sampling can offer an effectivesolution. Over the lastten yearsthe acoustic activity of four specieshave been monitored on an ocean-scalebasis in the north Pacificand North Atlanticusing the Navy'sSOSUS network Watkinset a/,2000,Charif et a!.2001!. Resultsprovide large scale patterns of vocalactivity throughout the yearin areaswhere animals e.g.,humpbacks! are knownto breed.Surprisingly, however, for pelagicspecies with no known breedingor calvinggrounds, singing occurs throughout most of theyear even during the feeding seasonin high latitude areas Figure 3!,

Proceedingsfrom the InternationalWorkshop on theApplications of PassiveAcoustics to Fisheries 113 Forregional-scale sampling, autonomous seaffoor recorders have been used in conjunctionwith visualsurveys aircraft or vessels!to estimatespecies densities and with active acoustic surveys to studythe relationshipbetween whales and the physicaland biologicaloceanographic conditions, Theresults from such integrated efforts are immensely more informative than any one survey methodalone, The number of casesin whichacoustics detected species first andmore often than visualsurvey is increasing,even for speciesthat areplentiful and highlyvisible.

Incases where a highlyfocused effort is required, for example,when conducting a visual-acoustic censusor testingspecific hypotheses regarding sound function, a varietyof hydrophonesystems canbe used,This includes sparse arrays of hydrophones,distributed networks of autonomous seafloorrecorders or a towedbearnforming arrays Clark et al.1996; Clark and Fristrup 1997; Croll et al.2002!. Such techniques provide mechanisms to continuouslydescribe the number,locations and movements of individual animals in great detail. When combined with data from other focused field methodssuch as photo-id and biopsy sampling, one ran relateage, sex, breeding status and behaviorof individualswithin a populationto theiracoustic behaviors e.g., Croll et a/. 2002!. Integrated approachesoffer tremendous opportunities for expandingcritical knowledge in suchdiverse areas as marine vertebrate mating strategiesand human impacts on the marine environment.

Acknowledgements Thebasis for thissynthesis comes from several decades of researchsponsored by the National GeographicSociety, New York Zoological Society, National Science Foundation, Naval Research Lab, NorthSlope Borough Department of WildlifeManagement, and the Officeof NavalResearch. Jack Bradbury,Donald Croll, William Ellison, Leila Hatch and Roger Payne provided stimulating discus- sions.I amindebted to all the staff in the BioacousticsResearch Program for assistancewith data collection, analysis,and interpretation.

References Charif,R, AClapharn, P.J. and Clark, C.W. 2001. Acoustic detections of singinghumpback whales in deep waters off the British Isles.Mar. Mamm. Science17!:751-768,

Clark,C.W., Charif, R., Mitchell, S.,and Colby,J,1996. Distribution and Behaviorof the Bowhead Whale,8alaenamysticetus, Based on Analysisof AcousticData Collected During the 1993Spring Mig ration off Point Barrow,Alaska. Rep. int. Whal. Cornmn. 46: 541-552.

Clark,C.W., and Ellison, W.T. In press.Potential use of low-frequencysounds by baleen whales for probingthe environment:evidence from modelsand empiricalmeasurements. in Echolocation in Batsand Dolphins J. Thomas, C. Moss and M.Vater, eds.!. The University of ChicagoPress.

Clark,C Wand Fristrup, K. 1997, Whales'95: A combinedvisual and acoustic survey of blueand fin

Proceedingsfrom the International8'orkshop on the Applicationsof PassiveAcoustics to Fisheries 114 whalesoff southern California.Rep. Int, Whal. Commn.47:583-600.

Croll,D, A,, Clark, C.W., Acevedo, A., Tershy, B., Flores, SGedamke, J. and Urban,J. 2002.Only males fin whales sing loud songs. Nature 417:809.

Richardson, W J., C, R,Greene, Jr., C. I. Malme, and D. H,Thomson. 1995. Marine Mammals and Noise. AcademicPress, New York,576 pp.

Watkins,W.A., M.A. Daher, G. M, Reppucci,J. E.George, D. L. Martin, N. A. DiMarzio,and D. P.Gannon. 2000.Seasonality and distributionof whalecalls in the North Pacific.Oceanography 13:62-67.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 115 lltustrationsand Diagrams

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Figurel. Spectrogramsofblue and humpback songs to illustratedifferences in ocousticcharocteristics for species predominantlyfrom pelagic blue! and coastal humpback! habitats.

Figure2. Spectra solid lines! for pelagic blue!and coastal humpback! species overlaid on ambientnoise spectra dashed lines! for the two different habitats.

Proceedingsfrom the International IVorkshop on the Applications of PassiveAcoustics to Fisheries 116 ~ ~Multihydrophonelocalization of low frequency broadband sources

Stephen E. Forsythe

Naval UnderseaWarfare Center, 1176 Howeil Ave, Newport Rl 02841 USA, [email protected]

Introduction

To localize high areasof fish activity and adequately characterizefish behavior,it is useful to localize individualfish by their emittedsounds over a rangeof 10s-100sof meters,In theory,one canuse multiple hydrophonesdistributed in spaceto localizea sourceposition/direction: using time-of- flight differencesamong the hydrophones,generate multiple hyperboloids then solve for the sur- faces'intersection to give a unique position for the source,perhaps in the least-squaressense. In practice,this is difficult f'or low frequency signals generated by fish thumps, etc.! becausethe onsetsof the signalsare not well defined.By using cross correlations among the receivedsignals as a "fuzzy"measure of time differenceit is possibieto do the equivalentof the intersectinghyper- boloidscalculation with an uncertainmeasure of time differences,giving the equivalentof a probability density of sourcelocation over a predetermined spaceof a priori possible locations.

The proposed method of tracking should be flexible, easily deployed, and self-calibrating.A useful side benefit of this kind of computerized fish tracking is to provide a record of vocalizations for later processing,

Prior art: conventionalbeamforming approach A conventionalbeamformer coherently adds the outputsof severalhydrophones using time delays per hydrophoneto emphasizeenergy arriving from a particulardirection andto suppressenergy arrivingfrom otherdirections!. In general,the spacingamong hydrophones must be severaltimes the wavelength of the detected sound to form an accurate estimate of direction; in addition, con- ventionalarrays of hydrophoneshave ambiguity in locatinga soundsource e.g.,the angulararnbi- guity around a line array!,

Alternative:Position estimates from time differencesamong hydrophone pairs An alternative to bearnforming is to use a "loose"array of hydrophones with an irregular geometry to performthe localization.In this method,hydrophones are used in pairs.For each pair, correlated pulsesof soundarriving with a timedifference t betweenhydrophones correspond to a single

Proceedingsfrom the international Workshopon the Appiications of PassiveAcoustics to Fisheries 117 sourcewhose position lies on a hyperboloidwith the hydrophonepair at the foci.Using several pairsof hydrophonesreduces the problemof locationto finding the intersection possibly in the leastsquares sense! of severalhyperboloids. The problem with this methodis that uncertaintyin the required t producesan uncertainestimate of the hyperboloids'intersections.This uncertainty is relativelysmall for high frequencyclicks, but is greaterat low frequenciesor for narrowbandsignals tike thumps and whistles,

Toovercome the effectsof uncertainty,it is usefulto keepthe estimatesof t "fuzzy"by replacingthe number by a probabilitydistribution around the mostlikely t. The useof statisticsderived from the crosscorrelation functions between pairs of hydrophonesdoes exactly this. Data from multiple hydrophonepairs can be fusedinto a singlecoherent picture by combiningstatistics from several hydrophone pairs in a mannerto multiplying probabilities of independent events to obtain the probability of all events occurring simultaneously.

Positionestimation experiment Totest the effectivenessof the localizationtechnique,5 hydrophones were deployed in a lake,The hydrophoneswere arranged as verticesof an inverted square pyramid l meter on a side with the apex 1 meter beiow the base.

Figure1 belowshows the "fuzzy"surface mapped as a Mercatorprojection using elevation from the horizontalplane and "longitude" around the equator!formed from the magnitudeof the cross correlationfunction of a cusk-eelsound as measured by a pairof hydrophonesin the array,The dark redareas are the mostlikely positions of the sourceas measured by the magnitudeof the crosscorrelation of the two hydrophones'signals.Figure 2 representsthe product of the first two cross correlation magnitudes.

Theimprovement using just two pairsis dramatic,Finally, figure 3 belowshows the resultsof including all hydrophone pairs in the product.

Discussion

Thetechnique described above performs well in a low-noiseenvironment. By simulation, several potentialsources of errorwere modeled using the acousticdata gatheredin the originalexperi- rnent. The error sources considered were

Uncertainty in hydrophone positions contaminatesall measurements!;

2. Uncertainty in signal arrival times;

3, Signalsat hydrophones not exact copies of source directivity of source!; 4. Reverberation images of the signal from boundaries!;

5. Ambient noise;

Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 118 6. Overlapping signalsfrom multiple sources.

Of the 6 sourcesof error,the mostdamaging were numbers 4 and6. Becausethe estimationprocess usedhas a nonlinearcomponent productof magnitudes!,multiple signals received simultaneously fromthe same type of fishgenerate multiple cross correlation peaks. These in turngenerate spurious product terms when multiplied together to form the final estimate.The minimization of this effect is the subject of future research.

Proceedingsfrom the international lrl'orkshopon the Appiications of PassiveAcoustics to Fisheries 119 Illustrationsand Diagrams

Figure1. Magnitude of thebroadband cross correlation dB relative to max!for 2 hydrophones apex and 1base!,

Figure2. product of correlationmagnitudes for the first 2 hydrophonepairs,

Proceedingsfrom the international Workshopon the Applications ot PassiveAcoustics to Fisheries 120 Figure3. product of magni tvdesof all hydrophonepairs.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 121 Illustrationsand Diagrams

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Figure3. Daily counts of blue toppanel! and humpback bottom panel! singers detected on SOSUSarraysin the westernhlorth Atlantic over a threeyear period.

Proceedingsfrom the /nternationalNlorlrshop on the Applicationsof PassiveAcoustics to Fisheries 122 PassiveDetection andLocalization ofTransient Signals from Marine Mammals usingWidely SpacedBottom Mounted Hydrophonesin Open Ocean Environments

Susan 3arvis and David Moretti NavalUndersea Warfare Center Division NewportEngineering,Test and EvaluationDepartment 1'I 76 Howell St., Newport, R.l. 02841-1708

Abstract Oneobjective of the MarineMammal Monitoring on NavyRanges project is to useexisting Navy undersearange infrastructure to develop a toolset for passivedetection and localization of marine mammals.The Office of NavalResearch funded the M3Rproject as part of the Navy'seffort to determine the effects of acoustic emissionson marine mammalsand threatened/ endangeredspecies. A necessaryfirst step in this effort is the creationof a baselineof behaviorwhich requires long-term monitoringof marinemammals. Such monitoring, in turn, requiresthe abilityto detectand localize the animals,This paper will present algorithms for passivedetection and localizationof transient signalsdeveloped as part of the M3Rtoolset. It wiII also present results of the application of these tools to detection and tracking of various toothed whales at the Atlantic UnderseaTest and Evaluation Center AUTEC!, Andros Island, Bahamas.

Introduction

Navy undersearanges such as the Atlantic UnderseaTest and EvaiuationCenter AUTEC!use arrays of widely spaced bottom mounted hydrophonesto acousticallytrack underseaand surfacevehicles. Traditionally,the vehiclesare equipped with acousticpingers that emit knownidentification signals at knownrepetition rates. Increasingly, range instrumentation infrastructure Figure 1! is being appliedto non-traditionaltracking problems, The Marine Mammal Monitoring on NavyUndersea Ranges M3R!program has developed a set of signal processingtools to detect and track marine mammalsusing Navy range facilities [11. Under the M3Rprogram, algorithms were developed to automatically detect and track two classes of whale vocalizations clicks and whisties. Both of these classesof signals are transient in nature. The tool set was recently tested at AUTECover a two- weekperiod. Over five hundredsquare nautical miles of oceanwere simultaneously monitored via 68 broad-bandhydrophones. Several species of toothedwhales where automatically detected and trackedin real-time.The positionalaccuracy of the M3Rtracking tools was confirmed by visual sightings by a surfacecraft and by manual analysisof the hydrophone data.

Proceedingsfrom the international workshop on the Applications of PassiveAcoustics to Fisheries 123 Discussion Visualsightings [2] and auralanalysis of hydrophonerecordings [3] indicatethat manyspecies of toothed whalesare presentat AUTEC.The mostcommonly seen and heardare spermwhales, dol- phinsand short finned pilot whales,all of whichare present nearly year round. Consequently,the M3Rtools weredeveloped to detect and trackthese common species. For purposes of algorithm development, the vocaiizations produced by the whales were characterizedas clicks and whistles. Clicksare, in general,any impulsive,broad-band signal. However, sperm whale clicks were of particular interest.Sperm whale clicks are very distinct,have high sourcelevel, and occurin regularpat- terns [4] or "clicktrains" Figure2!, Whistles were more broadly defined as any narrowbandevent that sweepsin frequencyover time Figure3!.

Thereare three distinct partsto the whale localizationproblem. First the vocalizationsor whale callsmust be automaticallydetected. In orderto determinethe positionof the animalin three dimensions,a givencall mustbe detectedon a minimumof four hydrophones.The second part of the problemis the associationof the detectionsreceived on varioushydrophones with eachother. Thatis, one must be able to determinethat the call received on hydrophone A at time tA is the samesignal that wasreceived by hydrophone B attime tB. Finally, associated sets of arrivaltimes areinput into a multilaterationalgorithm to solvefor position.A three-dimensionalhyperbolic positioning model [5] is usedto determinethe vocalizinganimal's location in X,Y, and Z aswell asthe time of emission of the call.

M3Remploys a real-timefrequency domain energy detector for whalecall detection. A spectrogram of the incomingacoustic data from each of thehydrophones isformed using 512-point fast Fourier transforms FFT! with a rectangularwindow and fifty percentoverlap. The resultant spectrogram hasa frequencyresolution of approximately51 Hzand a timeresolution of approximately9.8 ms. Eachtime-frequency bin of the spectrogramis comparedto a timevarying threshold, D f t!. The thresholdis set to be m dBabove the time! averagepower within frequencybin f.The output of the detector,Q~ t!,f for eachhydrophone, is a binaryvalued "detection spectrogram" which contains a 1 in eachtime-frequency bin that exceededD f t! anda 0everywhere else Figure4!. The detection spectrogramindicates, in real-time,the presenceof whalevocalizations as well asproviding infor- mationon their frequencycontent. As evidentin Figures2 and3, the signalstructure of sperm whale!clicks is very differentfrom the signalstructure of whistles.Therefore, separate detection associationalgorithms were developed for eachsignal type.

A seriesof clicks from a single sperm whale exhibits nearly the same inter-click interval on ail receiv- ing hydrophones.Calls from eachadditional animal exhibit their own uniquepattern. In fact,inter- clickinterval patterns were found to be an effectivemeans of both differentiatingbetween individ- ualwhales and associatingpatterns of detectionsamong hydrophones [6]. In the first stepof the M3Rclick association algorithm the time-frequencydetection spectra from all hydrophoneswere reduced to binary "click maps".Click maps contain a 1 for time indices where broad band events occurredin the detectionspectrum and 0 forall other times Figure 5!. Conceptually,the next step is to crosscorrelate the clickmaps from severalhydrophones with a masterhydrophone to Findthe difference in time of arrival between each hydrophone and the master. However,care must be

Proceedingsfrom the international Workshop on the Applications of PassiveAcovstics to Rsheries 124 taken in implementing the crosscorrelation in order to properly associateeach click detection amongthe hydrophones.Figure 6a showsan exampleof a clickmap from a singlehydrophone containingclicks from two individuals,Figure 6b showsthe clickmap from a secondhydrophone overthe sametime period.The question is which clicksin figure6b belongto whichindividual?

TheM3R click association algorithm uses the notionof a "scanningsieve" [7] to matchdetection pat- ternsbetween hydrophones. The sequence of cilickdetections i.e. click map! within the scanning sieveon the masterchannel is comparedto the clicksmaps from surroundinghydrophones "scanned"signals!. The scanning sieve time window always starts on a click detection, and is moved acrossthe scannedsignal one click detection at a time, That is,the resultant correlation valueat anytime delayrepresents the numberof matchesbetween the masterchannel pattern startinga specificclick and the scannedchannel pattern starting at a specificclick, The delay of the rnaxirnum correlation value represents the difference in time of arrival where the first clicks in the scanningsieve and the scannedsignal were best aligned. The output of the scanningsieve process are sets of time difference of arrival TDOA! for each click detection received on the master channe! Figure7!. TheTDOA data from eachhydrophone are then histogrammedto estimatethe number of separablesources Figure 8!, Onlydetections associated with significantpopulations are used Figure9!. Theseassociated TDOA sets are then sentto the AUTECmultilateration tracking algorithm which calculates3D position.

Whistle vocalizations do not typically follow known repetition patterns. An individual can emit a single short whistle or groups of sweepsthat last severalseconds or both. However,the time-frequency characteristicsof the calls in whatever sequencethey may occur remain the same on all receivinghydrophones. To determine the TDOAof signalsamong the hydrophones,the detection spectrogramsQ f t! of the availablehydrophones are cross-correlated against a masterchannel, M [8].The cross correlation C tg between the i-th channel and the masterchannel is calculatedover a time window of approximately6 to 10 seconds.That time windowis then advancedby onehalf its duration and Ci tg is updated,

Ci t,x!=ZZQ~ f,t!Qi f,t+~!

Thetime delayassociated with the peakof the correlationfunctions indicates the TDOAfor a signal relativeto the masterhydrophone Figure 10a!. If whistlesfrom multiplewhales are presentwithin a crosscorrelation time window,multiple correlation peaks will be evident Figure10b!. Note that if both clicksand whistlesare present at the sametime, sperm whale clicks will dominatethe detection spectra.Correlation peaks due to whistlesignals will be obscured.Therefore, for practicalpur- poses,broad-band click events should be removedfrom the detectionspectra prior to crosscorrelation.

Whilecross correlation of detectionspectra indicates times of signalarrival and the presenceof multiplewhales, it doesnot associatethe time delaysof the correlationpeaks with an individual acrossthe hydrophonechannels. However, as mentionedearly, the sequenceof whistlesfrom an individualis the sameon all receivinghydrophones. Figure 11 shows the time differencesof arrival relative to a master hydrophone of the correlation peaksfor five hydrophones. Notice that there are

Proceedingsfrom the internationalWorkshop on the Appiicationsof PassiveAcoustics to Fisheries 125 two distinctpatterns of detectionsversus time along specific time delays. Matching these patterns alongtime delaysassociates the TDOA'samong the hydrophoneswith an individualwhale.

Associatedsets of TDOAcan then be the sentto the multilaterationtracking algorithm which calculates 3D position.

Recent Results TheM3R toolset was demonstrated at AUTECas part of a jointexperiment with researchersfrom WoodsHole Oceanographic Institution WHOI!. The WHOI team was testing a newwhale tagging system[9]. TheM3R algorithms were used with sixty-eightof the AUTEChydrophones to monitor over500 sq. NMi. When marine mammals were localized, their positions were relayed to thetagging vessel,which then endeavoredto maneuverclose enough to placea tag.

Thedetection, association and tracking algorithms described in Section2.0 were implemented to runin real-timefor arrays of fiveto sevenhydrophones. Given that there were 68 hydrophones to monitor,other display tools were used to broadlylocate whales before applying the high resolution positioningalgorithm. The Circle display is a Matlabprogram that showsthe numberof detections on eachhydrophone by drawinga circlearound the respectivehydrophone. The number of detections per minuteis mappedto the colorof the circle.Figure 12 showsan exampleof the Circledis- playwhile two groups of whaleswere on the range.The bright circles around Hydrophone 85 were causedby a singleclicking sperm whale. The bright circles around Hydrophone 53 were caused by a groupof pilot whalesjust off the range hydrophones47,48, 54 and55 werenot monitored!.The WHOIteam successfully tagged two of the pilot whalesshortly after this picturewas taken.

Thestrip chart program displays the detection spectrogram from a particularhydrophone in realtime. Theprogram reads the detectiondata from a serverprocess allowing the user to runmultiple chartson multiplecomputers simultaneously. During the AUTECtests this display was quite handy for monitoringphones over a widearea. At varioustimes, both broad sperm whales clicks, and pilot whale clicks and whistles were evident Figure 13!.

Boththe click association and whistle association algorithms worked well during the exercise. Vocalizingwhales were hearcf on rangealmost everyday, At differenttimes, individuals and/or groupsof spermwhales, short finned pilot whales,roughed toothed dolphins,melon headed whalesand even a beakedwhale were all detected and tracked by the M3R algorithms. The track positionsproduced by M3Rwere confirmed by GPSreadings and visual observations from the tag- gingvessel, as well as by manualmonitoring of the hydrophones.Figures 14a-b show an example of real-timeX-Y position and depth plots for a groupof two or threesperm whales. The depth plot indicatesthat thesewhales were likelyperforming deep feeding dives. On somedives monitored duringthe test, sperm whales were tracked at depthsof 1000to 1200m. Figure14c shows the depthtrack for a singlesperm whale that was performing shallow, near-surface dives. Figure 15 showsthe real-timeX-Y position plot for a groupof whistlers,which were later identified by WHOI team members as roughed toothed dolphins and melon headed whales.

Proceedingsfrom the international Workshopon the Applicationsof PassiveAcoustics to Fisheries 126 Summary TheM3R project has developed algorithms for the passivedetection and tracking of marinemam- malsusing widely spaced, bottom-mounted hydrophones characteristic of Navy undersea tracking ranges.While these algorithms have been implemented and testedfor deploymentat the AUTEC, theyare applicable to anyfixed or portablerange that usesrnultilateration tracking algorithms. Potentialranges with the hardware to supportthe M3Rsystem include the Pacific Missile Range Facility,the Southern California Offshore Acoustic Range, and any of theNavy's various portable sys- terns.

TheM3R algorithms have been designed to work in a highlychannelized multi-processor hardware environment,and the softwarearchitecture has been developed to be fully networkcompatible. Signaldetection, and detection-association algorithms for two primarytypes of whalecalls, whistles andclicks, have been developed. These algorithms are specifically designed to beused with widely spacedsensors, and assumethat the marinemammals vocalize repetitively with sufficientsource levelsto be detectedon multiple hydrophones.

TheM3R algorithms, for bothclicks and whistles, have been successfully demonstrated resulting in realtime 3Dtracking of severalspecies of toothed whalesincluding sperm whales, rough toothed dolphins,melon headed whales and pilot whales.The M3Rtool set allows automated collection of datapreviously unavailable for the long-termmonitoring of marinemammal bioacoustics within their naturalenvironment, This opportunity hasbeen created with minimalinvestment in infra- structureby providingNavy ranges as a dual-useasset. Research applications of the M3Rsystem include the ability to remotely estimate marine mammal abundance, assessmentof bioacoustic behavioralbaselines, and evaluationof the impactof anthropogenicnoise compared to thosebase- lines.

Acknowledgements

We would like to acknowledge our sponsor,Dr. Robert Gisiner,at the Office of NavalResearch, for fundingthis project. We would also like to thankthe AUTEC personnel, especially Thomas Szlyk, for accessto their considerableinfrastructure and ongoing support. In addition,we would liketo thank the NUWCDivision Newport ILIR program manager, Richard Philips, for supportingthe initiative to createa baselinesperm whale bioacoustic characterization in the Tongueof the Ocean TOTO!.

References [1] Moretti,D., eI al.,"MarineMammal Monitoring on NavyRanges M3R!", Proceedings of the UnderseaDefenseTechnology Hawaii 2001 Conference,October 2001,

[2] NavalUndersea Warfare Center Detachment AUTEC,"Final Environmental Review, Adoption of a RangeManagement Planfor the Atlantic UnderseaTest and Evaluation Center AUTEC!,Andros

Proceedingsfrom the lnlernationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 127 Island,Bahamas", p. 57,September 1997,

[3] Perkins,P.J,, "Bioacoustics at AUTEC, Bahamas: A Surveyand Guide",Naval Undersea Systems Center Technical Mernorandurn 87-2018, 1987,

[4] JaquetN., Dawson S., and Douglas L.,"Vocal behavior of malesperm whales; Why do theyclick?", Journalof the AcousticalSociety of America,Vol.109 S!,pp, 2254-2259, 2001.

[5] Vincent,H., "Models, Algorithms, and Measurements for UnderwaterAcoustic Positioning",Ph.D. Dissertation.University of Rhode Island,Kingston, R.I.,2001.

[6] WardJ.,"Sperm Whale Bioacoustic Characterization at the Tongueof the Ocean,Bahamas U!," NUWCDIVNPTTM-01-106, Naval Undersea Warfare Center, Division Newport, Rl, December 2001 Unclassified!.

[7] Hu,Jand H.Vincent,"A Real-Time Multi-Hydrophone Data Association Algorithm for Marine MammalTransient Signals" ,NUWCDIVNPT TM-01-107, Naval Undersea Warfare Center, Division Newport, Rl. December 2001 Unclassified!.

[8] Moretti,D., et al"OpenOcean Marine Mammal Monitoring Using Wideily Spaced Bottom Mounted Hydrophones U!",to appear in Journal of Underwater Acoustics,2002,

[9] Tyack,P., et al.,"Acoustic Response and Detectionof MarineMammals Using and Advanced DigitalAcoustic Recording Tag - C51188",www.serdp.org/reportong/reporting.html.

Proceedingsfrom t'he InternationalWorkshop on the AppIicationsof PassiveAcoustics to Fisheries 128 , ths!f'.Mj Figure1: A JTEChas sixty eight broadband bottom mounted hydrophones with a 2A%i baseline.

6'gure2: Spectrogramshowing sperm whale clicksfrom severalindividuals,

Figure3: Spectrogramshowing a sequenceof whistles probably from a shortfinned pilot whale

proceedings from the inter»ational Yrorkshopon the Application.. of passiveAcoustics to Fisheries 129 Figure4: Detectionspectra-gram, 0 f t!, of whistles.Threshold was set 6-d8 above the average spectrai power.

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Figure5: Clickmaps are formed by summing the detection spectrum above! along frequency then thresholding the sums.The red curveindicatesthe click map for this data.

Proceedingsfrom the internationalIrIrorkshop on the Apph'cationsof'Passive Acoustics to Fisheries 'l 30 tx«««neinal Ala!«Dca«ct«ann!«n. S n«a«an 'Sn««nac I«« .! 1' sinn«an1 ! [ ...... Oa«ncce I I O «11-

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Figure6: Clickmaps for two hydrophonescontaining clicks from twoindividuals. itis not evidentwhich clicks received by hydrophoneB areassociated with Source1 or Source2.

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Figure7: Preliminary output of the M3Rclick associationalgorithm showing the estimated TDOAbetween the scanning sieve,hydrophone 61 1,and five additionalhydrophones

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries '1 31 Figure8: Aboveisthe output of theclick association algorithm for hydrophone6 12 indicated in purpieinfigure 7!, Twoseparate ti mesof arrivalare evidentindicating the presence of 2 whales.A histogramof theTDOA data shows two significantpopulations.

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Figure9i Finaloutput of theclick association algorithm for calls from a singlesperm whole, The points indicate the TDOAat whichthe algorithm found the best matches between the scanning sieve and theclicks maps of hydrophones605, 603,604,612 and 606 relative to masterhydrophone,611, Notice the minimal scatter of theTDOA points.

Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 132 Figure 10:

a!Resultsof crosscorrelation indicating the TDOAof the signal from one whale.

b!Cross correlation results indicating the TDOA'sof signalsfrom two whales,

TvroW~

Figure1 1;TDOA data resulting from cross correlations of fivehydro phones against a masterhydrophone. Two indi- vidualwhales show two distinct patterns indicated by purple and green boxes! of detectionsversus time along specific TDOA's.

Proceedingsfrom the internationalWorkshop on theApplications of PassiveAcoustics to Fisheries 333 Figure12: Circle detection count display, Maps color of thecircle around a hydrophoneto thenumber of detection per minute.

Figure13: Strip chart displays scroll horizontally todisplay detection spectra for a given hydrophone in realtime. Thetop rightand lowerleft chartsshow sperm whale clicks while the top left and lower right show whistles.

Proceedingsfram the internationalWorkshop an the Applicationsaf PassiveAcoustics ta Fisheries 134 b!

Figure14: Examp!esof position and depth plots for spermwhales.a! Real-timeX-Ydisplay for agroupof2 « or 3individuals. b! Thedepth plot Forthat group. c! A depthplot showing the shallow divesof a singlesperm- whale.

Figure 15:Areal-time X-Y position plot for multiple whistlers.Theicon shapesindicatetheindividuals that the NR toolswere ab!e to identify.This group was observed by researchers aboard the O'HOi whale tagging vessel. The group consistedof more than twenty roughed tootheddolphins and melon headedwhales.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 135 ' Synchronized underwater audio-video recording

Phillip S. Lobel

Boston University Marine Program,Marine Biological Laboratory Woods Hole, MA 02543

Extracted from: Lobel P.S.2001 Fish bioacousticsand behavior:passive acoustic detection and the applicationof a closed-circuitrebreather for field study.Marine Technology Society Journal, 35;19-28

Introduction Oneadvanced technique used in undersearesearch to studyfish acousticbehavior is simplythe interdisciplinary application of established acoustic technology combined with new mini-video camerasand hydrophoneswhile diving with a UBArebreather. Rebreathers and hydrophoneshave beenaround for morethan 40 yearsbut it hasbeen only in the lastdecade that videocameras and hydrophoneshave become miniaturized. Most importantly, these video cameras are equipped with audioinput enablingsynchronous audio-video recording. Acoustic signal analysis is alsogreatly simplifiedby directconnections to advancedportable computers and new soundanalysis software. Evenso, the basicsituation is the samenow aswhen Steinberg and Koczy964! stated,"the prino- ple accomplishmentof the techniquesfor underwaterobservation is that of extendingman's senses of sight and hearing underwater".

Beingable to observeand recordthe sonicbehavior of marineanimals was recognized as an irnpor- tant scientific approach to understanding fish behavior ever since it was first revealedthat sounds wereintegral to behaviorin manyspecies Fish 1954, Griffin 1955, Moulton 1958,Tavolga 1960!. The approach that I usein recording bioacousticswas pioneered in the 1960'sat the LernerMarine Laboratoryin Bimini,Bahamas and during missionsof the underwaterhabitat, TEKTITE. In 1963, a televisionand hydrophonesystem was deployed in about20m depth and linkedby cableto the Lernerlab with a roomfull of electronicequipment for recording see figures in Kronengoldet al, 1964!.This system recorded a varietyof soundsbut the fixedcamera did not usuallycatch the identity of the soundproducer Kumpf1964!. This early system did, however, clearly document several temporalpatterns of distinctivesound production by marineanimals Cummings et al,1964!.This systemwas also used for the playbackof soundsto determinethe effectivenessof pulsedlow frequencysounds for attractingsharks and other fishes Richard 1968, Myrberg et al.1969!.Duringthe TEKTITEmissions of 1969, divers used rebreathers from an underwater habitat to record fish sounds usinga Bmmfilm moviecamera and a tape-recorderwith hydrophoneoperated independently but simultaneously Bright 1972!. Bright clearly noted the benefitof the noiselessrebreather when

Proceedingsfrom the InternationalWorkshop on theApplications of PassiveAcoustics to Fisheries 136 recordingfish behavior.The two majoradvances today are 1!advanced video and hydrophonetech- nologyenabling truly synchronousaudio recording in a muchsmaller package! and 2! the increasedreliability of electronic rebreather systems.

Bubble Noise Bubblesnot only producenoisy sounds but alsonear-field vibrations in the water Fig.1,2!. This waterdisturbance is probablysimilar to the hydrodynamicdisturbances produced by fast moving predatorsto which mostfish areespecially sensitive by meansof their lateralline and sensorypore system.The common range of reeffish hearingis roughlybetween 20 and 1000Hz although some hearingspecialist species can hear in rangesup to 10 KHz.Oneherring species can hearat 180KHz Hawkins 1981,Mann et al.1997, Popper and Fay 1998!.However, it is fair to note that some fish apparentlyhabituate to boatand scubanoise, as is seenat somemarine protected areas or other sites with high diver activities.For example, I recently recorded a situation where scubaand exces- siveboat noisedid not affectthe matingactivity of the damselfish,Dascyllus reticulatus in a lagoon Lobel pers.obs., Saipan,July 2000!.

I started recording the acoustic behavior of free ranging fishes in 1988 using open circuit scubaand first generation8mm camcordersconnected to a hydrophone Label 1992!. Because of the scuba bubbles,I hadto spendmany hours per day in the waterto allowthe subjectfish to habituateto my presence,This required remaining motionless on the bottomfor long periodsand carefullycontrol- ling my breathingso that only a trickleof tiny bubbleswas slowly exhaled Figure3!.This somewhat avoided the louder noise caused by a big burst of bubbles from a singleexhalation, In order to obtain quality acoustic recordings without scuba bubble noise interference,acoustic measurements were edited in the lab from those portions of the video made between breaths. Thus, divers needed to be verydisciplined in their respiratorypace and activitywhiie recording.

We started using a rebreatherthree years ago and, without a doubt,it is the most successful methodfor obtainingfish behavioraland bioacousticdata Lobeland Kerr,pers. obs!. Beginning with myfirst field experiencewith the rebreather after31 yearsof scuba!,I wasgreatly impressed with howdifferently fish behavedwhen there wereno bubbles.The great advantage of the rebreatheris to allow usto approachanimals more closely. But this is alsoa bit morerisky for the same reason.I havefound that eels and grey reef sharksare more inquisitive and approach much closerwithout noisybubbles. On the other hand,the only time I experienceda schoolof juvenile parrotfishactually swim toward and over me,as if I wasjust a rock,was when usinga rebreather. Thisaspect of usingrebreathers will haveits mostsignificant impact on the practiceof conducting underwater transects for speciescensus and abundance surveys.We havefound that we see more individuals and a greater diversity,especially large fishes,while diving with the rebreather Lobel and Kerrpers. obs.!. Taking this one stepfurther, we haverecently acquired camouflage pattern wet- suits that are made to blend in with reef habitat. Thus,divers not only make no noise,but their sil- houettesare lessconspicuous and makethe diverappear less like a largepredator. Underwater photographerswere among the first to userebreathers routinely for the samereasons e.g. Cranston

Proceedingsfrom the international Workshop on the Applications of PassiveAcoustics to Fisheries 137 1993!.Any type of observationaldata that marinebiologists collect will clearlybenefit from using the rebreather.Examples include: 1! conductingtransects to determinespecies diversity and abundance,2!quantifying fish feedinghabits by observation,and 3! definingspecies habitat usage and behavior.Such field projectsrequire a toolthat providesthe greatestdegree of scientificaccuracy possibleand confidencein the results.The advantage of the rebreatheris that it allowsfor; 1! noise- lessoperations,2! the long bottom time necessaryto allowfish to acclimateto the observer'spres- ence overall,the useof a rebreathergreatly reduces the time neededto habituatefishes compared to opencircuit!, and 3! sufficientdive time to recordentire courtshipand spawningactivities. The unit only releasesa limited amount of bubbles when ascending due to expansionand overflow of gasesin the scrubber assembly,

Acknowledgernent Fundingfor the field and laboratorystudies is supportedby the ArmyResearch Office DAAG55-98- 1-0304and DAAD19-02-1-0218!.My participationin this meetingwas supported by the WoodsHole SEAGRANT office,

References LobelP.S. 2001 Fishbioacoustics and behavior:passive acoustic detection and the applicationof a closed-circuitrebreather for field study.Marine Technology Society Journal, 35:19-28

Proceedings rom the international Workshopon the Applications of PassiveAcoustics to Fisheries 138 Figure1. Recordingfishes undervvater using a videocamera and hydrophone.Photo by LisaKerr LobeL

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 339 David A, Mann

Universityof SouthFlorida, College of MarineScience, 140 Seventh Avenue South, St. Petersburg, FL, 33701 USA. dmann@marine,usf.edu

Introduction Passiveacoustic detection of fish soundsrelies heavily on advancesin recordingand data processing technology. The recent explosion in fast, inexpensive personal computers and electronics has createdtremendous growth potentialin the field. Thispaper describes early efforts in developing passiveacoustic detection systems for fishesand morerecent efforts utilizing digital systems,The goalsof eachof thesesystems were to automaticallydetect and quantifysounds of interestin realtime, minimize false detections, and minimize the amount of data that needs to be stored to deter- rnine calling ratescontinuously over long periodsof time.

FirstGeneration Passive Acoustic Detection System Mostfish soundsare either simple pulsed broad-band sounds or tonal type sounds,where the pulse ratesor dominant frequency are species-specific e.g.Lobel and Mann, 1995;Mann and Lobel,1998; reviewed in Zelick et a!., 1999!. Fishsounds do not typically exhibit complex frequency modulations seen in many marine mammal vocalizations. This makes it possibie to describe most fish sounds with a fewmetrics, such as sound duration, peak frequency, and bandwidth.Timing between pulses can be recordedby storingthe time of onsetof eachpulse. By recording these simple metrics, a system canbe developedto automaticallydetect and processsounds of interestand greatly reduce the amount of data that would be acquired by simply recording continuously,

Earlyattempts at passiveacoustic detection involved developing a largelyanalog system that would detect soundsthat were above some background level and store the time of occurrenceand soundduration actualsound data were not stored! Mannand Lobel,1995! Fig.1!. Fromthese data,the rateof soundproduction of differentspecies'sounds could be determined.This system was employed to measuresound production rates of individual damselfish over periods of months, and revealeda strikingdawn chorus in sound productionand a tight link betweensound production and spawning cycles Mann and Lobel,1995!.

Proceedingsfrom the internationai Workshop on the Appiications of PassiveAcoustics to Fisheries 140 Real-TimeDigital SignalProcessing Systems Whilethe analogsystem was a robustdetector, continued increases in data storagecapacities and the emergenceof inexpensivedigital signalprocessing chips and the flexibility that theseprovide, promptedthe developmentof a programmabledigital system.This system is commerciallypro- ducedby Tucker-Davis Technologies Gainesville, FL! and consistsof a battery-powereddatalogger with two channelsof A/D,32MB of RAM,and a graphicalprogramming interface. The fiexibility of the dataloggeris that it canbe usedto processthe signalin real-timeincluding a widearray of fil- tering FlR,IIR! techniques and adaptive thresholding. The datalogger can be programmedto store whateverdata is desiredby the researcher,To demonstrateits flexibility,a devicewas programmed to detect the sounds produced by the toadfish Opsanusbeta, store the time of occurrenceof the soundand recorda 1000-pointsound sample Fig 2!.

The Future of Fisheries Bioacoustics Theprimary tools for the fish bioacoustician will remainthe PCand continuous digital recording systemsfor sometime. Topromote the emergenceof fisheriesbioacoustics requires more research intothe sounds made by different fish species and the developmentof newtechnologies that uti- lize these data.

Ultimatelyfisheries bioacoustics should move the wayof fisheriesacoustics where the signal output is not the actualsound data, but the locationsand intensityof fish spawning.

A usefulanalogy is the developmentof SONARsystems for fish quantification.These systems do not deliver raw sound data to the researcher.They return processeddata on fish location and abundance.One can envision the daywhen real-timefisheries bioacoustics systems will producemaps of the locationsof sound-producingfishes that can providemanagers with data on the temporal and spatial extent of spawning.

Acknowledgments My introductionand passionfor the field of passiveacoustic detection was driven by my Ph.D.advi- sor PhillipLobel. Support for the developmentof the digital dataloggerwas provided to TDTby an NIH grant to the author.

References Lobel,PS. and D,A,Mann. 1995. Spawning sounds of the damselfish,Dascyllus albisella Pomacentridae!,and relationshipto male size.Bioacoustics 6: 187-198.

Mann,D A.,and PS.Lobel,1995. Passive acoustic detection of soundsproduced by the damselfish, Dascyllus albisella Pomacentridae!. Bioacoustics 6: 199-213.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 141 Mann,D.A., and PS.Label. 1998. Acoustic behavior of the damselfishDascyllus albisella: behavioral and geographic variation. Environ,Biol. Fish. 51:421-428.

Zelick,R,, D.A. Mann, and A.N. Popper. 1999. Acoustic communication in fishesand frogs.ln: ComparativeHearing: Fish and Amphibians. Springer, New York. pp. 363-411.

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcovstics to Fisheries 142 Illustrationsand Diagrams

Ms@DBI4cloR

Figure1. Signalprocessing scheme for thedetectionofdamselfish Dascyllusalbisella! calls.

Figure2, Spectrogramof a seriesof automatically detectedtoadfish Opsanusbeta! callsplotted one after another. Thedominant frequencyof thesecalls is approximately250 Hz.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 143 ' Potentialforthe ose of Remotely Operated Vehicles ROVs! asa platformfor passive acoustics.

Rodney Rountree',Francis Juanes', and Joseph E.Blue'

'ProgramManager, Mount Hope Bay Natural Laboratory, School for MarineScience and Technology, UMASS Dartmouth, 706 Rodney French Blvd., New Bedford, MA 02744-1221 rrountree@UMassD,Edu

'Department of Natural Resources,University of Massachusetts,Amherst, MA 01003

'President,Leviathan Legacy, inc.,3313 Northglen Drive, Orlando, FL 32806 [email protected]

Introduction

We are still largely ignorant of the distribution and behaviorof the great majority of marine fish. Possiblyone of the greatestchallenges to researchersattempting to studythe behavioralecology of fishes is that of finding the fish in the first place.Since some fish are soniferous,acoustic detection and tracking may offer methods of population assessmentfor management decisions. Passive acoustic techniques can be a valuable tool for the identification of essential fish habitats EFH! for soniferousspecies. These techniques can allowfor non-destructivesurveys of largeareas to pin- point habitatsfrequented by soniferousspecies, particularly during spawningevents when vocal activity tends to be greatest.Studies of fish sounds can provide a wealth of data on temporal and spatial distribution patterns,habitat use,and spawning,feeding, and predator avoidance behaviors. Currently most investigatorsuse simple omnidirectional hydrophones and can usually only locate the general area of a spawningaggregation, but haveoften been forced to use circumstantial evidence of the identity and behavior of the calling species e.g.Saucer and Baltz 1993,Luczkovich et al. 1999a,b!.Attempts to use passiveacoustics as a tool to identify EFHbased on spatial patterns in sound productionis alsocritically hampered by the lackof sufficientdata describing the sound characteristicsof individual speciesand behaviorsunder field conditions. We propose that acoustic technologies utilizing hydrophone arraysto horne in on sound sourcescan greatly improve the study of soniferousfishes and their habitatrequirements. First, homing in on soundsources will provide a valuablenew tool to validate the identity of sound producers,especially when coupled with underwater photography or video devices. Second,the ability to home in on vocal fishes would enhanceour ability to correlate fish sound production with specific locations and habitats. ln this paper,we describe our preliminary attempts to develop a SoniferousFish Locator SFL!for use with a remotely operated vehicle ROV! to home in on fish sound sources and make recornmenda- tions for future efforts.

Proceedingsfrom the international Workshopon the Apph'cationsof PassiveAcoustics to Fisheries 144 Tracking and Homing Basics The use of passiveacoustics for horning was developed for naval warfare during and before WW II,A passiveacoustics horning systemwas irnplernented on torpedoes for destruction of ships and submarines.The technique of horningwas extended to detectionand tracking of submarinesby sonobuoysduring World ll. These systems were developed before the adventof small,fast comput- ersand wereimplemented with electronicsthat arenow known as operational amplifiers. Adequate Signal-to-Noiseratios were required for implementingthese techniques. Homing on shipsand submarinesby torpedoesrequires only 2 directionalhydrophones because the torpedobody blocks out soundfrom behindit. The available aperture is smallso frequencies such that there areseveral wavelengthsacross the directionalhydrophones are used for the lowestfrequency in the tracking bandwidth.The torpedo determines the bearingfrom acousticsignature signal!of the ship or submarine by cross-correlatingthe signaturesfrom the 2 hydrophones.The cross-correlationfunction ls: t+T/2 C" t!= 1/TI [s> t!s2 dtt+v!] as t-T/2 wheres t! ands2 t!are the noise-freetime signalsfrom the 2 hydrophones,~isthe time delay betweenthe arrivalsof the signalsat their respectivehydrophones and T isthe periodover which thecross-correlation isestimated. The longer T is,the better the cross-correlation estimate E[C>2 ~!]. For this function, there are 2 bearingsor valuesof that can arisefor the maximum value of E[C,z x!].One representsthe backdirection that we know is wrong becausethe body of the torpedo blocksout that backdirection. The other bearingthen hasto be the correctone, Hydrophone separation,x, in homingtorpedoes is smallbut a relativelybroad segment of the noisespectra is available to provide sufficient bearing accuracyfor tracking.

Thecross-correlation function of Equation! cannotbe realizedin practicebut only estimated. Accuracyof the estimatedepends primarily on 1! signal-to-noiseratio SNR!,2!bandwidth of the signaland 3! separationof the hydrophones,Obviously for widerseparations, bearing accuracy is better.The choice of hydrophoneseparation is a compromiseimposed by the operationalrequire- rnentsarising when onewishes to placehydrophones on an ROV.Loss of coherencedepends on environmental conditions and their effect on propagation of sound, I ossof coherence is more severeat the higher frequencies,but it is not an important factor for arraysthat will fit on an ROV. Forlarge signal bandwidths, the peakof the cross-correlationfunction is narrow.When estimating the cross-correlationfunction, the time gateT imposesa sinxf!/xf type functionupon the estimate that,along with SNR,determines how accuratelyone can track a fish.When the bandwidthis large and SNRhigh, one canchoose a smalltime windowand/or a smallhydrophone separation and get good homing results.

Proceedingsfrom the Internationall/l/orkshop on theApplications of PassiveAcoustics to Fisheries 145 Methods TheSFL was designed to work basedon the well-understoodprinciple of null steeringon an acousticsource with two cardiodhydrophones Fig. 1!. Specifically, the SFLconsists of three hydrophonesconfigured to formtwo orthogonal cardiods shown by the solid and dotted lines Fig. 1!. Thetwo cardiodsare 180degrees out of phasewith eachother in this configuration.Electronic summingof the two cardiodsresults in a nullalong the x-axis Fig.1!. A bearingto a soundsource is obtained by rotating the SFLuntil the sound direction is coincident with the null. To enable an operatorto determinebearing, output from the SFLwill be sentto both earphonesand a recording device,The null is found by listeningto the summedoutput of the two cardiodsin one earwhile simultaneouslylistening to the soundintensity with the other ear.Feeding output from cardiod1 prior to summation with cardiod 2 to the second earphone channel eliminates noise from behind the SFL soundfrom behindthe SFLis nulledout by the cardiod,Fig.1!. Hence, the operatorlistens onlyto the intensityof soundscoming from in frontof theSFL. This is an important property of the SFLthat reducesinterference due to ROVnoise and/or boat noisewhen operating in shallowwater. Thedistances, d,separating the hydrophonescan be changed to increaseor decreasethe sensitivity of the dipoleand allow the operatorto tune the rnaximurnsensitivity toward the predominantfre- quencyband of the type of soniferousfish speciesfor whichhe/she is searching.

Initialtests of the feasibilityof deployingan arrayof hydrophoneson a PhantomIII modelROV as part of the SFLwere conducted in test tanks located at the Northeast-GreatLakes Center for the National Under Sea ResearchProgram at Avery Pt.Connecticut in October 2001. Testwere conducted on the array configuration, attachment methods and ROVnoise production. The ROVwas not ableto supporta hydrophonearray in the requiredconfiguration Fig. 1! becauseof ballastprob- lems.We therefore had to modifythe configurationso that the hydrophonearray could be supported by the ROVframe Fig.2!. Unfortunately,this configurationdoes not allowfor the cancellationof ROVnoise the arraymust be forwardof the noisesource as in Fig.1!. Withthis configuration,noise levelsunder various operating conditions were tested; 1! with all thrusters off andthe ROVsitting on the bottom, 2! with top thrusters on,3! with rear thrusters on, and 4! with all thrusters on,

Fieldtesting was conducted within the StellwagenBank National Marine Sanctuary on boardthe R/VConnecticut from October17-24, 2001. Ten ROV dives were conducted in sand,gravel and boul- der habitatswithin the sanctuary.Operations were conducted in depthsof up to 70 m undersome- tirnesharsh environmental conditions and strong tidal currents.To reduce ship noise, ROV dives wereconducted while the shipwas at anchorand runningoff of its generators.The array was corn- posedof threeTH608-40 model hydrophones made by EngineeringAcoustics, Inc 933Lewis Drive, SuiteC, Winter Park, FL 32789!. The hydrophones had a nominalsensitivity at the preamplifierout- put of -160.5dB, The 3-channelaudio data from the arraywas captured to a laptopPC with a 4- channelI/O boardand NIDisksoftware supplied by EngineeringDesign 3 NewtonSt,, Belmont, MA 02478!.Sound signal processing was conducted using Signal 4.0 EngineeringDesign!. A 1k Hz sinewave was played through a portableCD player into the systemand the input voltagerecorded at the beginningof eachROV dive. This allowed calibration of the systemgain, in additionto the hydrophone.A singlechannel of audiodata was simultaneously recorded to video both Hi-8and

Proceedingsfrom the International IIirorkshopon the Applications of PassiveAcoustics to Fisheries 146 VHS!for backup. The calibration signal was also recordedto the videotape so that calibrated audio data can be obtained directly from the tapes to obtain signal source levels,

Results Tanktests revealed a veryhigh levelof noise,even with the thrustersturned off and the ROVsitting motionlesson the bottom of the tank Fig.3!. Althoughnoise levels were highly variable, we esti- matedlevels of >130dBV with thrusteroff and >160dBV with all thrusterson, Thehigh levelof noiseprecluded the operationof the SFLwith a "flying"ROV, with the currentarray configuration. We therefore decided to modify the operation of the ROVwhile in the field in order to increasethe signal to noise ratio enough to obtain bearing information, We required the ROVto remain stationary with its thrustersturned off long enoughto acquirethe bearingto the soundsource.

Withall thrusterson, the ROVproduced high levels of soundat bothhigh and low frequencies Fig. 4!. Dominantfrequencies were centered on 7-8kMz. While the stationaryROV was significantly qui- eter,it still generatedsubstantial noise centered on 8 kHz Fig.5!. Thelow frequencynoise in Fig.5 is an artifactresulting from mechanicalbanging, rubbing and tapping on the tank sidesby techni- cians testing sound reception.

Recordingfish soundsin the field with an arrayattached to the ROVproved to be verydifficult in practice.Strong currents limited our abilityto remainstationary on the bottom.The ROV was rarely ableto maintainits positionon the bottomfor morethan a fewminutes before the operatorwas forcedto turn on its thrustersto stabilizethe vehicle,This aiso required the operatorto turn on the ROVlights, thus further disturbingthe fishes.Fish sounds were recorded on onlyone occasion whenwe wereable to maintainthe ROVon the bottomwith its thrustersand lightsoff Fig.6!. A prolongedseries of low thumpsand growlsfrom a singlefish wererecorded over a 20minute period whenthe ROVwas sitting stationarywith its lightsoff. Duringthis time a largecusk, Brosme brosme,was frequently observed hanging around the ROV.It is highlylikely that the cuskis the sourceof the recordedsounds. We estimated the ambientnoise ROV+ship + seas!level at around 134dBV and the cuskcall at around140 dBV. At othertimes when the lightsand thrusters were on, cuskwere only observedin a highlyagitated state, and appearedto stronglyavoid the ROV.

Discussion Basedon preliminaryanalysis of thesedata we feelthat the conceptof a SoniferousLocator Device isviable. However, current ROV designs preclude optimal configuration of thehydrophone array, requiringthe SFLto be operatedin a stationarymode. We propose that a vehiclespecifically designedfor low noiseproduction and capable of carryingan SFLwith a 2-3rn baseline in its nose would providean excitingnew passiveacoustic tool for soniferousfish surveys,The low callingrate of thefish recorded in thisstudy demonstrates that it wouldbe difficult to trackfish using the manual null steeringmethod proposed.Faster digital tracking using this sameprincipal would correct

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 147 thisproblem and should be implemented infuture efforts. However, it is important to pointout that datacollected during this cruise demonstrates that an ROV can serve as an adequate vehicle for the collectionof underwateracoustic data even without the SFL. The ROV with a hydrophoneattached wouldbe used to locatean optimum location and then would be set down on the bottom to record sounds.In this way,a rovingsurvey could be conducted. Althoughcusk have long been considered to be soniferous because ofthe presence ofa sonicrnus- cle,they had never been recorded until Norwegian scientists recently recorded their spawning sounds Aud Void Soldal, Institute of MarineResearch, Norway, pers. Cornrn.!. The calls apparently resemblehaddock spawning calls and are very different from those we recorded during this study. Ourrecordings were conducted well outside of thespawning season for cusk,so the sounds were likelyassociated with other behavior feeding or territorial display!. Observations made subsequent tothis study revealed that cusk vigorously guard the chum bag attached to theROV and frequently chaseaway other fishes, suggesting the species ishighiy aggressive and territorial. Because solittle is knownof the cusk'sbehavior, ecology and habitatrequirements, and becauseit appearsto respondwell to a stationaryROV with its lights turned off, it makesa promisingfield study animal for passive acoustics. A secondaryoutcome of the cruise was that we obtained sufficient video data to suggestthat the behaviorof somespecies is strongly influenced by the ROV and/or the ROVlights. Adult cunner, Tautogoladrusadsperus, redfish, Sebastes fasciatus, and pollock, Pollachius virens, obviously avoided the ROVduring the day, but pollockwere strongly attracted to the ROVat nightdue to ouruse of churnand bright lights. The chum attracted swarms of amphipodsthat in turnattracted a large aggregationof pollock as well as haddock, cod and skates. Cusk were only observed inboulder habitatand avoided the mobileROV both during the day and night when the lightswere on. When onlyinfrared lights were used, the cusk was clearly attracted to thechum bag on the ROV and showedno avoidanceof a stationaryROV. Contrastingly, species such as cunner, redfish and silver hakeappear to avoidthe ROVregardless of whetherits lightsare on or off,or whetherit ismoving or stationary.The response of thecusk to the mobileROV with its lightsturned on suggestthe speciesstrongly avoids the ROV.It couldnot bedetermined whether the lightsor theROV noise causedthis avoidance, however subsequent observations of cusk behavior indicate no avoidance of stationarycameras with white lights. We suggest then, that the noise generated by the ROV can be a significantsource of biasin studiesusing ROVs for fishcensus.

Acknowledgements Wethank Meghan Hendry-Brogan for diligentwork in boththe field and laboratory to collectand processfish sound data. Rebecca Jordan and David Howe assisted in thefield. This project received majorfunding from the Northeastand Great Lakes National Undersea Research Center, which also providedextensive logistical support, The Woods Hole Sea Grant College Program also provided supportingfunds. The Sounds Conservancy, Quebec-Labrador Foundation/Atlantic Center for the Environmentprovided a stipendfor Megan'sfieldwork

Proceedingsfrom the internationaiI/I/orkshop on theApplications of PassiveAcoustics to Fisheries 148 Literature Cited Luczkovich,J,J., H J.Daniel, ill., M.W. Sprague, S.E. Johnson, R.C. Pullinger, T.Jenkins, and M. Hutchinson.1999, Characterization of criticalspawning habitats of weakfish,spotted seatrout and red drum in Pamlico Sound using hydrophone surveys. Final Reportand Annual Performance Report Grant F-62-1and F-62-2,Funded by the U.S.Department of the interior, Fishand Wildlife Servicein Cooperation with the North Carolina Department of Environmentand Natural Resources, Division of Marine Fisheries,Morehead City, NC 28557. 128 p,

Luczkovich,J J.,M WSprague, 5 E.Johnson, and R,C. Pullinger. 1999. Delimiting spawning areas of weakfishCynoscion regalis Family Sciaenidae! in Pamlico Sound, North Carolina using passive hydroacoustic surveys,Bioacoustics 10:143-160.

Saucier,M.H., and D.M.Baltz, 1993, Spawning site selectionby spottedseatrout, Cynoscion nebulosus, and black drum, Pogoniascrornis, ln Louisiana.Env. Biol. Fish. 36;257-272.

Proceeciingsfrom the international8'oriishop on the Applicationsof PassiveAcoustics to Fisheries 149 Illustrationsand Diagrams

Figure1. Illustration of theprinciple of nullsteering on an acoustic source with two cardiod hydrophones. The SoniferousFishLocator consists ofthree hydrophones H1-H3! configured toform two orthogonal cardiods shown by thesolid and dotted lines. The two cordi ods are 180 degrees out of phasewi th each other. Summing the two results in a nuIIalong the xaxis. A bearingto a soundsourceis obtained by rotatingthe SFL until thesource directionis coincident with the null.

Figure2. Schematicillustrationof the hydrophone array configuration and attachment to thePhantom ill ROV,

Proceedingsfrom the InternationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 150 Figure 3.Tank test of noisegeneration by the ROI/with all thrustersoff lower left!, top thrusterson lower right!, back thrusterson upperleft! ond all thrusterson upper right!. Digitizedat 20 k Hz.

%+fWtf8C'

Figure 4. Noise generation from the ROIrwith all thrusters on. Recorded at 20 kHz.

Proceedingsfrom the lntemationa Ilorkshap on the Applications of PassiveAcoustics to Fisheries l5 I

~Quantifying ~ ~ ~ Species-Spe«ific ~ ~ Contributions ~ ~ tothe Overall Sound Level

Mark W.Sprague and Joseph J.Luczkovich'

'Dept, of Physics,East Carolina University, Greenville, NC 27858,USA spraguernNlrnail.ecu.edu

'Inst.for Coastaland Marine Resources and Dept. of Biology,East Carolina University, Greenville, NC 27858, USA [email protected]

Introduction Manyfishes are soniferous sound-producing! and producespecies-specific sounds Fishand Mowbray1970, Sprague et al.2000!. The sound production of an individualfish or groupof fishes can be usedto determinetheir presencein an areaand asan indicationof courtshipand spawning behavior. Often,we would like to quantify the sound production of a particular individual or species,but howdo we separatethat soundfrom other soundsthat aresimultaneously produced by biologicalsources, wave noise, and anthropogenic sources such as boatsand ships?A short answer to this question is to use a portion of the sound in which the desired source dominates over all others. This portion could be a time segment in which the desired source is much louder than the background i,eall other sounds!,a portionof the frequencyspectrum in whichthe desired source is much louder than the background,or a combination of these techniques.

Separating and CombiningSounds Parseval'sTheorem tells us that the squared-pressureof each frequency component contributes additively to the time-averagedoverall squared-pressureP

ln other words,each frequency component in a powerspectrum or sonogrammakes an additive contributionto the total soundpower because sound power is proportionalto the squared-pressure.Also, when sounds are mutually incoherent i.euoriginating from sourcesnot correlatedin time!,their time-averagedsquared-pressures, P>'!,v and P2!gy add to givethe squared-pressureof the combined sound,

Proceedingsfrom the International Mlorkshopon the Applications of PassiveAcoustics to Fisheries 153 P av P] !gv+ Pz!gy !

Equation! appliesto mostfish and backgroundsounds because most naturally-occurring sounds are incoherent.

Thetotal sound pressure leveI SPL! is also calculated from P avusing the relationship pi SPX= 10jog,~, ! P, wherePo is the referencepressure pPafor underwateracoustics!, To combine two mutuallyinco- herentsounds with SPLsSPL1 and SPL2, we must convert each SPL to a squared-pressureusing the inverseof Equation ! before adding them. The combined SPLis SPL=10log0~~'+10 ~" !. !

Equation! can be usedto combineor separatethe SPLsof varioussources, including fish sounds and the background.

BackgroundCorrection Function Cbg Pierce989! developed a background correction function Chg, based on Equation !, to determine thesound pressure level of a sourceSPL1 when background noise is present:

SPQ= SPY,-C IIhSPZ!.

In Equation!, isthe difference between the source and background SPLs and SPLtot is the total soundpressure level, The Cbg technique isinaccurate when ASPL<3dB because small inaccuracies inthe measurement of lead to large inaccuracies inSPL1, Figure 1 showsa plot of Chg vs. ASPL. Whena soundis 10dB or moreabove the background,the total SPLis the sameas the SPLof the sound i.e., APL is zero!.

In orderto determinethe sourceSPL using, the total SPLand the backgroundSPL must be measured.

Proceedingsfrom the internationalWorkshop on the Applicationsof Passive Acoustics to Fisheries 154 Ijsing the BackgroundCorrection Factor to Determine Silver PerchSPL Werecorded an individual silver perch Bairdiella chrysoura in WallaceChannel, NC, USA using a hydrophoneand video camera attached to a remoteoperated vehicle ROV! placed on the seafloor in 10 rn of water, The video confirmed that the fish made sound as it swam close to the hydrophone.A spectrogramof the recording is shown in Luczkovichand Sprague these proceedings!.We estimated the backgroundSPL by measuringthe sound levels between the pulsesin the silverperch call and determined thesilver perch SPL by subtracting Cl,g from the total SPL during the pulses.The sound was sampled at 24kHz, and we computed SPLs from the time-averaged squared-pressurein 1024-point Hanning windows. Each consecutive window overlapped the previ- ouswindow by 512sample points to insurethat eachsample point occurrednear the centerof at leastone sample window. The peaks of thebackground SPL were interpolated to givean upper estimateof thebackground SPL, and the valleys were interpolated to givea lowerestimate. Figure 2 showsan interpolated plot of thetotal and the maximumand minimum background SPL as well asthe silver perch SPL The maximum silver perch SPL was 129 dB usingeither the maximumor minimum background SPL!.

SpectralAnalysis of Soundsand SciaenidEgg Identification Wehave established a correlation between sound levels produced by Sciaenid fishes and the presenceof fertilizedsciaenid-type eggs in ParnlicoSound Luczkovichet al. 1999,Luczkovich and Spraguethese proceedings!. We conducted planktonic egg surveys at suspectedweakfish Cynoscionregalis and silver perch spawning sites using 28-cm diameter bongo net with 500 m meshtowed at thesurface for 5 minto capturethe buoyanteggs. We recorded the drumming soundsat thesame location before and after the tow andcompared the species-specific power spectraldensity PSD! in a 10-saverage power spectrum to the measuredegg density. The weakfish PSDwas taken as the sumof thePSDs in thepower spectrum from 304-375 Hz and the silverperch PSDthe sumthe PSDsfrom 984-1078Hz Spragueet a!.2000!,We assumed,based on our mtDNA RFLPanalysis of sciaenid-typeeggs and the results of Danieland Graves 993!, that eggs less than 0,8 m werethose of silverperch and those greater than 0.85 m werethose of weakfish.The regres- sionrelationships of egg density vs. species-specific PSD, after log-transforming, are nearly iinear in bothcases with an R' of 0.38for weakfish and OA4 for silverperch. The large variations in the data couldbe the result of errorsassociated with the egg sampling technique. We believe that in many casesour egg sample nets did notcapture nearby eggs due to variationsin currents,patchiness in theegg distribution, and perhaps in thebuoyancy of theeggs dueto salinityfluctuations!, Despite thevariations, these data are significant and provide the basis for predictingthe egg production for each of these speciesfrom sound levelsin the future.

SilverPerch Acoustic Avoidance of BottlenoseDolphins Duringour study of sciaenidspawning areas, we noticed that silver perch aggregations would sud- denlybecome quiet when we heard bottlenose dolphin Tursiops truncatus signature whistles. To

Proceedingsfrom the Jnternationa/!4'orkshop on theApplications of PassiveAcoustics to Fisheries 155 verifyour observations,we playeda recordingof bottlenosedolphin signature whistles with frequencycontent 4-8 kHz!at similarsource levels to thoseproduced by bottlenosedolphins near a silverperch aggregation and found that the signature whistles significantly quieted the silverperch vocalizations Luczkovich et al. 2000!.We also played a 700-Hztone at the samesource level with no significant effect on the silver perch.

Wedetermined the silver perch PSD by summingthe PSDs in the powerspectrum for frequency componentsfrom 950-1200Hz,the frequencyrange where silver perch are dominant, for consecutive 10-saverage power spectra see Figure 3!. To determine the silver perch reaction to theplay- back,we took the difference between the measuredthe silver perch PSD immediately before play- backand during the intervalbetween 20-30 s afterplayback. Using an analysis of covariance ANCOVA!,we comparedthe decrease in silverperch PSD after playback of bottlenosedolphin whis- tlesto changesin silverperch PSD after the 700-Hz tones and also to spontaneousPSD changes beforeand 20-30 s afteran ad-hoc selected time in a 120-srecording of silverperch with nosound playback.The bottlenose dolphin whistle produced a significant9-dB decrease in silverperch SPL [ANCOVA, among playback treatment adjusted means!, among slopes of the regressionlines for eachtreatment!]. The silver perch responded to bottlenosedolphin signature whistles by reducing their sound production.

Conclusions Severaltechniques have been demonstrated for determiningthe soundlevel of an individualor speciesin the presenceof other soundsources, Each technique isolates a portionof the soundin whichthe desiredsource dominates over the others.The sound portion could be a timeinterval in whichthe desired source is much louder than the others or it couldbe a portionof thefrequency spectrumin whichthe desiredsource dominates. In somesituations, techniques that combinetime intervalsand characteristic frequency bands must be usedto separatethe contributionsof the desired source.

References Daniel,L. B. and Graves. J,E, 994! Morphometricand genetic identification of eggsof spring- spawning sciaenidsin lower ChesapeakeBay. Fish,Bull. 92,254-261.

Fish,M. P.and W. H.Mowbray. 970! Soundsof WesternNorth Atlantic Fishes. Johns Hopkins Press, Baltimore,209 pp,

Luczkovich,J.J., M WSprague, S.E. Johnson, and R C.Pullinger 999! Delimitingspawning areas of weakfish,Cynoscion regalis Family Sciaenidae! in Pamlico Sound, North Carolina using passive hydroacoustic surveys.Bioacoustics 10, 143-160.

Luczkovich,J.J., H.J. Daniel III, M. Hutchinson, T Jenkins, S.E. Johnson, R.C. Puliinger, and M, W.

Proceedingsfrom the InternationalIArorkshop on theApplications of PassiveAcoustics to Fisheries 156 Sprague.000! Soundsof sexand death in the sea:bottlenose dolphin whistles silence mating choruses of silver perch, Bioacoustics 11,323-334.

Pierce,A. D.989! Acousticsan introduction to its physicalprincipals and applications. Acoustical Society of America,Woodbury, NY, pp, 54-78,

Sprague,M.W., J.J. Luczkovich, R.C. Pullinger, S. E, Johnson, T. Jenkins, and H.J.Daniel III.000! Using spectralanalysis to identifydrumming sounds of someNorth Carolina fishes in the family Sciaenidae.Journal of the ElishaMitchell Society 116,124-145,

Proceedingsfrom the international Mlorkshopon the Applications of PassiveAcoustics to Fisheries 157 Illustrations and Diagrams

Figuret, Thebackground correctionfunction vs.the differencebetween the sourceand backgroundsound pressure levels. Theinset1989!iI table1mPierce, gives-values to 16 the nearest$5,25 decibel. 15,5The 16.background T51Tcorrection17.25 47.functionis 5 inoccurote for.

Tie e fel

Figure2. Soundpressure levels SPLs!in a silverperch sound recording at WallaceChannel, NC, USA, The solid line is thetotal SPL, the upper dashed line the maximum background SPL, the lower dashed line the minimum background SPL,and the dots the silverperch SPL calculated using the backgroundcorrection factor,

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 158 No Sound Played Whistle No Sound Played

21:43 21:44 21:45 21:46 21:47 21:48 Time h:min!

IQ O CO o 21:0521:06 21:07 21:08 21:09 21:10 Time h:min!

Figure3, Examplesofsilver perch species-specific PSDfluctuations upon playback of a bottlenosedolphin signature whistle above!and a 700-Hztone below!at the samesource level.

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 159 A remote-controlledinstrument platform for fish behaviour studiesand sound monitoring

Ingvald Svellingen,Bjern Totland,and JanTore 0vredal

Institute of Marine ResearchFish Capture Division PO.Box 'l 870 5817 Bergen Norway Email: [email protected], [email protected],jan.tore.ovredalOimr.no

Thispaper was originally presented as a posterat a symposiumtitled "Fish Bioacoustics". Thesyrnpo- siumwas held in Chicago,USA May 30-June 2,200'I. The paper will alsobe published in thejournal "Bioacoustics".

Introduction A newremote-controlled instrument platform for in situ recordingof behaviour-specificfish sound and synchronousvideo observations has been developed. Such studies have normally been carried out usinga cableconnection between the hydrophoneand the observingvessel, which must be positionedrelatively close to the hydrophoneitself and generatenoise. Vessel generated noise will not only affectthe recordedsound pattern, but mayalso have an impacton the behaviourof the fish studied,

The new remote-controlledplatform allows operation at distancesup to 10 nauticalmiles and has thereforebeen developed to omit suchproblems during behaviour studies of wild fish in their natural environments.

Description of the system The instrumentplatform consists of two mainunits fig 1!;a surfacebuoy and an underwaterelec- tronic bottle capableof operatingat depthsdown to 500m.The surface buoy contains a high- speed,full duplex, 11Skbps, data telemetry radio and a video link transmitter. It is connected to an underwater bottle via a 12 lead Kevlar cable. The underwater bottie is made of an anodized alu- minum cylindermounted on a stainlesssteel frame and housesa fullfeature single-board computer in orderto controlvarious instruments, and to logdata from different sensors. Two rechargeable batteriesprovide power,24 VDC, to the electronics.AIIelectronic parts have been chosen to rnini- rnizepower consumption, making it possibleto run the systemcontinuously for approximately20 hours before recharging.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 160 Forsound recording a hydrophoneis usedand connectedto the amplifierin the electronicbottle via a sub-seaconnector on the end lid.All amplifiersettings are fully remotecontrolled from the observingvessel via the radiotelemetry link, and its output is connectedto the PCsound card. The digitizedsignal is temporarilystored on a flashmemory in orderto avoidmechanical noise from a harddisk drive which might disturbthe receivedsignal. The recording program allows automatic frequency,level- and pre trigging facilities, which makes it suitablefor a selectivesound recording.

A low light video camera placed on the top of the bottle is usedfor simultaneousvideo observations.Both sound- and video signalsare transmitted to the observingvessel and monitoredin real time.

A number of sub-seaconnectors on the electronic bottie allow connection of different sensorsand equipmentlike pan/tilt unit,artificial light, echosounder etc., making the systemsuitable for a variety of tasks.Modification of the underwaterunit caneasily be doneto supportdifferent instrumentation needed for a wide range of studies.

Thevideo transmitter and the data link enablethe instrumentplatform to be operatedfrom an observingvessel at a distanceof up to 1 nauticalmiles for videotransfer, and up to 10nautical miles with data link only.

Theremote controlled instrument platform has so far beensuccessfully used to recordfish sounds withsynchronous video observations from cod, haddock, saithe, and tusk. The advantages of a remote-controlledinstrument platform over a systemwith long cabieshave been clearly demonstrated in these studies.

Proceedingsfrom the international Workshop on the Applications of PassiveAcoustics to Fisheries 161 Illustrationsand Diagrams

Fig.I. Fishbehovior and sound production can be monitored from a distancewith the remote-controlledinstrument platform, using radio link.

Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 162 Mark Wood

Biomathematicsand StatisticsScotland, Rowett ResearchInstitute, Greenburn Rd.,Aberdeen, AB21 9SB,Scotland, UK ma [email protected]

Introduction Manyspeoes of marinefish emit low frequencysounds composed of sequencesof nearlyidentical transientunits. The production of thesesounds is often coupledwith displaysof aggressionand/or courtship. In order to associatesound production with fish behaviour we need to be able to distin- guishbetween the soundsof differentspecies and betweenindividual fish to be ableto identify which fish is emitting sound at any given time.

Waveletshave been used to produce features of the waveforms which are then used to discriminate between the soundsfrom different fish. We consider the performance of this method for discriminatingbetween individual haddock, Melanogrammus aeglefinus, and for discriminatingbetween soundsfrom threefish species,the haddock,cod Gadusmorhua, and pollackPollachius pollachius,

Data

Recordingsof the haddock were made at the FRSMarine Laboratory,Aberdeen in a semi-annular tank 90m'!containing 3 maleand 5 femalefish. Thesounds were detected by a broad-band hydrophone,amplified and sampled at a frequencyof 8 kHz. The haddock were maintained under controlledconditions, and recordingswere made over two spawningseasons February-April,1999 and2000!. Haddock sounds consisted of long trainsof regularlyrepeated 'knocks'.

Figure1 showsa typicalrecording consisting of a seriesof regularlyspaced low frequencysound units,or knocks. Figure 2 showsthe different waveforms of the 3 male haddock. The haddock varied their sound by repeating these knocks at different rates.

Thecod sounds were recorded in the aquariumof the FRSMarine Laboratory and consisted of long grunts, produced singly or in groups of up to 5. The pollack sounds were recorded in the seaat a depthof 15min LochTorridon, Wester Ross, from a cageof fish,andconsisted of shortrepeated grunts. The sounds of all three speciesare described by Hawkins and Rasmussen978!,

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 163 Wavelets Waveletsare special mathematical functions, designed to overcomethe shortfallsof the well known FourierTransform, Wavelets are produced by scaling compressing or expanding! and shifting a sin- gie'mother'waveletalong the time axis. These wavelets are usually designed to forman orthonor- mal basis,in which any sound signal may be represented as a seriesof the scaledand shifted wavelets.The'amount'of each wavelet present in the decompositiondetermines the dominantfre- quencycomponents and their locationin the signal,For this reasonwe saythat the wavelettrans- form hasgood time and frequency localization.

Backgroundmaterialon wavelet analysis may be found in Jawerthand Sweldens994!, Bruceand Gao996! andAbrarnovich eral. 000!. A moremathematical treatment is given by Chui 992a,b! and Daubechies 992!.

Recognition of Individual Haddock Waveletswere usedto extract features from the sound units which would enable individual had- dockor differentspecies to beautomatically recognised. The procedure consisted of 4 steps. 1. Thesmoothing property of waveletswas used to automaticallyisolate individual sound units in therecordings, By setting certain smaller wavelet coefFicients to zero and then applying the inversewavelet transform we were able to extractindividual haddock knocks, or codand pol- lackgrunts from the background. These were extracted in 32mswindows containing 256 data points! and were standardisedso that their amplitude was of unit variance.

2. Due to the way in which the knocks were extracted in !, and the fact that the wavelet trans- formis sensitive to shiftsalong the timescale, the non-decimated or stationary!wavelet trans- formwas used to decomposethe knocks.A rnernberof the Coifletfamily of waveletswas found to give the best results. 3. Plotsof the non-decimatedwavelet coefficients in descendingorder of absolutevalue in each levelare very similar for soundsfrom the sameFish, but clearlydifferent for soundsfrom differ- entFish, These plots suggest suitable features for discriminatingbetween the knocksof individualmale haddock and betweendifferent Fish species. For haddock, a plotof the scoreson the Firsttwo canonicalvariates Krazanowski 996!! showedthree well separatedclusters. 4. Certainfeatures from ! wereselected and usedin a discriminantanalysis to allocateunclassi- Fiedknocks to oneof thethree male haddock or to eachof thethree species, or to a spurious sound,The method of extractingpulses in ! meantthat soundswere picked up whichwere notproduced by any of the malehaddock, cod or pollack.These spurious sounds, caused by splashesfor example,could not beeliminated and so were allocated to a fourthgroup.

Results and Conclusions In a testdata set of the haddocksounds, 175 knocks were detected as havingcome from fish A,336 from B,194 from C and 142 were spurious sounds. The classiFicationrates are shown in table 1. The overallsuccess rate was 89%. It wasshown that usingthe fact that knocks occurred in longrepeti- tive series increased the success rate to 95%.

Proceeclingsfrom the InternationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 164 Forthe allocationof soundsto differentspecies, 5 soundswere detected as having come from cod, 609 from haddock,151from pollack and 94 of the sounds were spurious. The classiFicationrates are shown in table 2. The overall success rate achieved was 83%.

Table 1, ClassiFication rates of individual haddock knocks

Table 2.Classificationrates of codi'haddock/pollacksounds

Waveletsprovide a usefulmethod of automaticsound recognition. The methods described above cancount and assigna largenumber of soundsfar morequickly than can be done by eye.This techniquehas the potential to separateFish sounds from ambient noise in the sea,and may provide a non-invasivemethod for locating spawning Fish.

Acknowledgements Wethank Professors I.T.Polliffe and A.D. Hawkins, University of Aberdeen,and Dr G. Horgan, Biomathematicsand StatisticsScotland, for their supervisionand input. Wethank LiciaCasaretto, FRSMarine Laboratory, for recordingthe haddock sounds, and Professor A.D. Hawkins for supplying the cod and pollack recordings.

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics t'o Fisheries 165 References Abrarnovich,F.,Bailey, TC.and Sapatinas, T.000! Waveletanalysis and its statisticalapplications, Journalof the RoyalStatistical Society, Series D,49!, 1-29.

Bruce,A. and Gao, Hong-Ye 996! Appliedwavelet analysis with S-PLUS,Springer-Veriag, New York.

Chui,C.K. 992a! An introduction to wavelets,Academic Press,Boston, MA.

Chui,C.K. 992b! Wavelets:a tutorialin theoryand applications,Academic Press, Boston, MA.

Daubechies,I 992! Tenlectures on wavelets,Society for Industrialand AppliedMathematics, Philadelphia.

Jawerth,B. and Sweldens, W.994! Anoverview of waveletbased multiresolution analyses, Society for Industrialand Applied Mathematics,36!,377-412.

Krazanowski,WJ. 996! Principlesof multivariateanalysis: A usersperspective, Oxford University Press, Oxford.

Hawkins,A.D. and Rasrnussen, K.J.978! Thecalls of gadoidfish, Journal of the MarineBiology Association U.K.,58,881-911.

Proceedingsfrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 166 illustrationsand Diagrams

0 10 0 2D D.25 time m!

Figure1 -Sound recording of o singlehaddock made in the tank

Figure2-The waveformproduced by thehaddock,

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries l67 Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 168 Section 3

Working Group Summaries

Proceedingsfrom the International Workshop on the Applications of PassiveAcoustics to Fisheries 169 ProceedingsFrom the internationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 170 A summaryreport on the Biology Session andBiology Working Group from the international Workshopon the Application of PassiveAcoustics in Fisheries.

Joseph J. Luczkovich

Institutefor Coastaland MarineResources, Department of Biology,East Carolina, University, Greenville, NC 27858

Summary Fishesare known sound-producers in the sea.Sound production is associatedwith mating,aggres- sion, and feeding in fishes, The soundsare species-specificin many cases,but the identification of fishesbased on soundproduction alone has led to rnis-identificationsin the past. Sound-truthing, or the identificationof species'soundshas been accomplished by useof recordingof individualsin aquariaand in situ using underwatervideo and audio.A libraryof knownfish soundsin being assembledand will be archivedat CornellLibrary of NaturalSounds. Data rescue of existingrecord- ingsthat arein dangerof beinglost due to ageand inadequate storage is underway,but needsare greatin this area.Sounds can be detectedover fairly long distances km!,so after sound-truthing and archiving of sounds,detection of the fish in an area by meansof passhveacoustics alone becomespossible, even if the fish has not been captured and observed.

Introduction Listento the fish? WhenI suggestthat theydo this,most peoplerespond that they werenot aware that fish produce sounds. Yet,Aristotle reported this phenomenon Historia Animalium,IV,9!, and NativeAmericans may have listened for underwatersounds to locategroups of fish while hunting them. Passiveacoustics has been used for over50 yearsin fish biologyand fisheries surveys see Fishetal,1952 and Fishand Mowbray1970 for a summaryof earlywork! and is beingused routinely todayto determinehabitat use,delineate and monitorspawning areas, and study the behaviorof fishes various papers presented in these proceedings!, Fishesproduce soundsto communicate with one another while they are feeding, mating,or being aggressiveand also make noisesassociat- ed with feedingand swimming.Over 700 species of fisheshave been identified as sound producers soniferousfishes! Kaatz 2002!. The purpose of thisreport is to summarizethe findings of the BiologyWorking Group that washeld on the third day of the workshop.The Biology Working Group was tasked with reviewing papers presentedduring the workshop,and information from the literature, and to summarize our state-of-knowledgeon passiveacoustics applications to fisheriesand the censusof marinelife. Specifically,the groupsought to identifyareas of that havebeen well

Proceedingsfrom the International tiIforkshopon the Applications of PassiveAcoustics to Fisheries 17I studied, as well as those in need of further research,and to set forth a list of researchareas that the workshopparticipants deemed of highestpriority.

Whathave we learnedin the workshopon the biologyof fisheryorganisms and fish from studying passive acoustics' Usinghydrophones, marine ecologists and fishery biologists have been able to listento the sounds fishesproduce and identify species-specific signatures using signal processing and spectral analysis computer algorithms. Often these sounds are very loud and dominate the acoustic environment wherethey occur, as in the drumfamily Sciaenidae, somuch so that theyinterfere with military and petroleumprospecting operations that invoiveacoustic monitoring. In other situations,such as damselfisheson coralreefs, the soundsare not loud andrequire specialized techniques to detect them Mann and Eobel 1995,Lobel and Mann 1995!.

The main problemthat hasbeen overcome in the pastby biologistsusing the passiveacoustic approachis to identifythe speciesproducing a sound:one first must do "sound-truthing"to discover which soundhas been produced by an individualfish. Thereare two mainways this hasbeen accomplished:! captivefish recordingsand ! in situ recordings.Most identifications of fish sounds in the past have been done using captive fishesthat produced sounds under conditions that are far from natural, Fishesheld in aquaria often do not exhibit natural behavior and sound productionis adverselyaffected. Although some fishes produce sounds naturally after capture in aquariumenvironments that mimic the environrnentinsitu, most do not, Investigatorshave resort- ed to mechanicalor someother kind of stimulation includingelectrical shock!! to producea distur- bancecall, which mayor maynot representthe soundsproduced by fishesin nature.As was dis- cussedat length,aquaria present their own seriesof technicaldifficulties, including tank echoes and backgroundproduced by airbubbles, pumps and motors, Yong Han and Joe Blue provided insight asto how thesedifficulties might be overcometo somedegree by properdesign of the aquarium. Verificationin situof the locationof the soundsource, sound source levels, and identity of the speciesinvolved is frequentlydifficult. One example of the difficulty in correctidentification was reportedby Spragueand Luczkovich001!, who correcteda long-standingerror in identificationof the "chatter"sound, originally attributed to weakfishby Fishand Mowbray970!, but nowknown to be producedby stripedcusk eel Mannet ai. 1997!.The problem of matchingsounds to speciesand behaviorsoccurs because of the limited abilityof biologiststo observefish producingsoundsin situ. Althoughsome observations have been made recently using underwater video in cieartropical reefwaters Mannand Lobel1998, Lobel 2001, and Lobelthese proceedings! and even in temperate environmentswith turbid waters Euczkovich and Sprague 2002; Rountree et ai.,these proceedings!, manyattempts to recordfishes have failed becauseof mechanicalsounds produced by the plat- forrn with the videocamera bubbles from SCUBAdivers, motors and propellersof ROVsand subs! to which fishesare extremely sensitive and which inhibit or maskfish soundproduction. Lobel 001! hasdeveloped underwater videography techniques that usecalibrated hydrophones and videocamerasoperated by diversusing a rebreatherapparatus, which producesno bubbles. Underwaterautonomous recording devices such as timer-operated sonobuoys have also been used

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 172 to detect the sounds produced by fishes and the acoustic avoidanceresponse produced when their bottienose dolphin predators also are detected on the recording Luczkovichet al. 2000!. Because there is no observer near the autonomous recording device,disturbances are minimized and natural behaviorcan be recorded,A futuregoal for identificationof speciessounds should be to develop combined acoustic and videotape recordersthat are triggered when sounds or water movementsof a specificlevel and type are detected,

Knowledgeof soundsource levels is importantfor calculatingthe detectionlimits in termsof area sampled! of hydrophones and sonobuoys.Sound in water is measuredas a Sound Pressurelevel SPL!in dB re 1 @Pa,which can be measuredwith calibratedhydrophones and recordingdevices. Luczkovichand Sprague002! reportedthat the soundsource level for an individualsilver perch Bairdiellachrysoura 1 rn from the hydrophone was 129 dB. Lobe!and Mann 995! measuredthe soundsource levels of the dominodarnselfish Dascyllus albisella and modeled the propagationof the sound Mann and Lobel 1997!. More precise measurementof sound source levels in the future will requirethat one knowboth the locationof the fish andthe hydrophone,so that proper assumptions can be applied to the calculation of sound transmission loss and the determination of acousticsampling areas Mannand Lobel1997!. Calibrated hydrophones and recordingdevices that areeasy to useare needed for suchstudies seeMann et al.,these proceedings, for a discussionof the recording technology available!,

Another problem discussedrelated to speciesidentification of fish sounds is the nomenclature usedto describethese sounds. Numerous investigators have used terms such as "grunts, "knocks", "snaps","pops" ,"staccato", "drumming" ,"humming" ,"rumbles" ,"percolating", "purring",etc.to describe the soundsheard; these names are often onomatopoeic.There was general agreement at the workshop that such names be used in the future in the published literature to describe a sound,but that there was a need to standardizeour names for fish sounds.This standardizationwill allow rapid communication between biologists and other observerswhile listening to unfamiliar sounds.Some biologistshave given different names to the samesounds; others have given the samename to a similarbut differentsounds produced by two species,even though the soundsdiffer between specieswhen examined spectrographically see below!. This can lead to confusion, and so as much aspossible unique names can be givenan individualsound "long-spine squirrelfish grunt" versus "silverperch long aggregatedgrunt"!. Standardizationof namesshould give priorityto previously publishednames whenever possible. Kaatz 002! suggesteda possibleapproach using a plotof soundduration vs. frequency, which allows a clusteringof similarsound types, so that we canname them accordingly.Thus a "hum"has a longduration at a particularlow frequency,whereas a "grunt" has a short duration at a low frequency,

One way to more precisely report a sound produced by a fish in captivity or in situ is to makea spectrographor "voiceprint" of the soundrecording. Sound spectral analysis software has been usedto great advantagein fish passiveacoustics surveys and archives. Fishery biologists should be aware of the established methods and pitfalls for doing such spectralanalysis of sounds.A primer

Proceedingsfrom the international6'orkshop on the Applicationsof PassiveAcoustics to Fisheries 173 on bioacousticsmay be neededfor the biologistnew to the field of passiveacoustics; this is avail- ablein Canaryfor Macintoshsound-analysis software package available at www.cornell.edu/lns! andsoon to be releasedin a PCWINDOWS version called RAVEN. Another primer is alsoavailable at the AcousticalSociety of Americawebsite www.asa.org!.In the past,species'sounds have been characterizedin terms of theirspectral properties, pulse repetition rates, dominant frequencies, and powerspectra using Fast Fourier Transforms FFTs!, which are available in mostsound analysis soft- wareprograms SpectroGram, CoolEdit, Canary, LabView, Avisoft, Spectraplus, Signal, Igor, etc.- see Mannetal.,these proceedings, for a discussionabout sound recording and analysis technology!.

Spectralanalysis has proved very usefulidentifying species and in separatingthe contributionof individualspeaes to the overallsound levels. The sound and egg productionof the sciaenidssilver perch,Bairdiella chrysoura, and weakfish,Cynoscion regalis, are correlated Luczkovichet al, 1999!. It wasknown from captivefish recordingsthat B.chrysoura and C.regalis have different dominant frequencies Sprague et a/.2000!. Using spectral analysis and Parcival'sTheorem, Sprague and Luczkovich these proceedings! have shown how the soundcontribution of eachspecies of sciaenid canbe separatedin a recordingthat containsmore than one species.This frequency-specific SPI canbe correlatedwith egg productionfrom eachspecies. A differentform of spectralanalysis calledwavlet analysis has been usedto identifyspecies and individualfish within a species Wood et a/.2002!.If we can recognizeindividuai fish on the basisof their wavelet"voice prints",then this wouldallow soniferous fish individuals to betagged and recaptured without humans having to capturethem in nets. Suchapproaches may revolutionize fishery biology for soniferousspecies, We canalso "clean up" noisy recordings using wavelets. Wavlet analysis shows great promise in future studiesto segregatethe soundsof multipleindividuals in largeaquaria and in situ.

Biologistshave been able to linkthe aggressiveand spawning behavior of fishesto theirsound pro- ductionusingin situ and tank studies. For example, Myrberg 972! andMyrberg et al. 986! has describedthe behavioralecology of the bicolordamselfish Stegastes partitus,which uses sounds bothin matingand in defenseof itsterritories. A similarpattern of soundproduction "popping" has been recorded by Lobel and Mann 995! and Mann and Label 998! for the domino damseilfish Dascyllusa/bise//a in the Pacific.The domino damselfish produces a visual"signal jump" display in conjunctionwith the soundproduction during courtship,The sound production and spawningfrequency can thus be monitored remotely over time using a hydrophone wired to a land-based microcomputer,a systemthat has been termed a "spawn-o-meter" Mann and Lobel 1995!. Mok and Gilrnore983! establishedthat spottedseatrout Cynoscion nebulosus Sciaenidae! sounds are associatedwith spawningby using both tank recordingsof matureripe seatroutand passive acoustic hydrophonesurveys combined with ichthyoplanktonsurveys. This approach has also been extended to the weakfishC. regalis by Luczkovichet al. 999!. Somework describingthe soundsproduced in associationwith spawningin haddockMe/anogrammus aeg/efinus has been described by Hawkinsand Amorim 000!, Hawkinset al. 002!, and Casarettoand Hawkins002!. Theseauthors describedthe completemating and courtship behavior of the haddock,with a detailedanalysis of thesound production at eachstep in themating sequence. This sort of basicbehavioral biology is stilllacking for mostfishes detected in passiveacoustic surveys. Without this type of behavioral study,we may know that a fishis present in anarea, but notwhat it isdoing there. So, improve-

Proceedingsfrom the /nternationalWorkshop on the Applicationsof PassiveAcoustics to Fisheries 174 ments in our ability to simultaneously observe fish and listen to them are needed,including better research aquaria and underwater video techniques.

Passiveacoustics approach provides a rapid way of establishing the spawning component of essential fish habitat EFH!.Delineation of spawning areashas been done Mok and Gilmore 1983,Saucier and Baltz,Luczkovich et ai.1999, Roumiliat et al.,Collins et al., Holt et al.,these proceedings!. But how far awayare the fish?Need to set standardsfor the differentlevels of EFHdata, Baltz thesepro- ceedings!described the different levels of EFHdata and suggested that passiveacoustics can be used to establish Level 1 data presence or absence in an area!.

What do we need to do in the future that will help fishery inanagersand fish biologiststo learn more about fishes and their sound production? Sound propagation in the marine environment, especially in shallow water,is a verycomplex problem. Someof the workshop participants gave some hints of what may be done by researchersin the area of passiveacoustics and fisheries in the future, SusanJarvis explained how sound propagation was studied by Navy scientistsfollowing sperm whales in the Bahamasswimming through the large hydrophone array set in place there for submarine sonar studies; although these whales make soundswith higher sourcesound pressurelevels, similar approaches could be used with fishes swimming through fixed hydrophone arrays. Scott Holt described the use of towed arraysto locate spawning areasof red drum along the Texascoast. By monitoring the sound levelsof a very loud and close by individual red drum, the multiple hydrophone elements on the towed array was useful in localizingthe individualsound-producing fish. Some new approachesto makingcaptive and in situ recordingscame out of the workshop. Joe Blue suggested using "butterfly" shapedtanks in captive fish recordings,because they reduce tank echoes.Tony Hawkins warned againstthe use of thin- walied fiberglasstanks surrounded by air,which can increasethe echo effect. Hawkinsthen describedhis combination approach of using an enclosure in the field to record haddock sounds, which provided a more natural acoustic environment without tank noise and echo problems. But, recorded sounds must be assumed to come from the fish, as one cannot screen out ambient sounds in the marine environment. Blue suggested putting the fish and the hydrophone in a narrow diameter pipe that is lessthan the wavelength of the sound that you are interested in recording. It may be difficult to get the fish to produce sounds in such an unnatural situation, however.Workshop participants described new acoustic devices for monitoring fish sounds,including the NURCROVs fitted with hydrophones,ECU and Navy Sonobuoys,and the NOAA/NMFSremote underwater device acousticrecording RUDAR!,and variousAUVs. One such AUV was a "glider",which produces very little sound itself becauseit usesa motor only to get to the surface,then glides to the bottom.

Becauseaquatic environments cover huge areasand great depths, acousticsholds great promise in locating fish that cannot be easily seen using ROVs,submarines, SCUBA or underwater video. Because light is attenuated more rapidly in water than sound, and sound waves in water travels 5 times the speed of sound waves in air,the detection of a fish speciesin an areawhere habitat sur- veysare conducted is far more likely than detection with nets and visual means.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 175 All workshopparticipants agreed that there wasa greatneed to conductstudies of fishesusing passiveacoustics in the future, Someareas of future researchneeds were suggested at the workshop, including:

1!. Quantificationof fish aggregationssize by useof passiveand activeacoustics used together. 2!. Linkingthe passive acoustical work to behavioralwork withmore video and audio recordings made together where visibility allows!.

3!. Modelling sound propagation of fish sounds in different environments. 4!, Correlationof soundsfrom speciFichabitats with overallenvironmental quality 5!. Developmentof directionalarrays and beam-formingtechnologies to preciselylocate the sound sources at dark or in turbid waters.

6!. Determination of the sizesof fishes making sounds and if both males and females make sounds in some species!. 7!. Theneed to establishwhat proportionof the fish arecalling at a giventime. 8!. Theneed to determineand modelhow soundpressure levels SPLs! vary with shoalsize and distance from sound source. 9!. Modellingof chorusingbehavior. Are individualfishes calling together, i.e., are the choruses synchronized? 10!.The need to securefunding for establishmentof long-termremote listening stations at estab- lishedsites so that spatialand temporal diurnal and seasonal!variations in sound are charac- terized. 11!.The need to establisha nationalcenter in the USfor the studyof bioacousticsof fishes. 12!.The need to do conductthese studies in waysthat will allowtesting of specificscientific hypothesesin collaborationswith physical,chemical, and biologicaloceanographers,

Thispartial list offuture researchdirections will be undertakenby individualsat the workshopand their colleaguesfrom traditional grant funding sources the NationalScience Foundation, Sea Grant Program, NOAA!.

Someobstacles must be overcomein the future casesof mistakenidentity haveoccurred in the past e.g.the stripedcusk-eel chatter sound was long confusedwith weakfish,Sprague and Luczkovich2001! and unknown sounds exist. Thus,there is an urgent need to have an archive of knownsounds that can be reliablyassociated with fish speciesand particularbehaviors. Such an archivehas been funded by ONRand is being assembledby bioacousticiansfrom the Libraryof NaturalSounds at CornellUniversity from thousands of hoursof underwaterrecordings of fishes andthe aquaticenvironments made by soentists Bloomgarden and Bradbury2002!. There is a needto establisha setof standardsfor vouchersounds, which should be separatedin the archivein termsof the speciestaxonomic affiliations, environmental conditions, and recordingenvironment. For example, in the archive we should differentiate between: ! Captive/tankrecordings - these are routinely done for "sound truthing".When there is only one speciesin the tank, there is no question as to which speciesproduced the sounds.But, what standardsshould be usedfor aquarium design, reduction of tankechoes and noises?

Proceedingsfrom the international Workshop on the Applications of PassiveAcoustics to Fisheries 176 ! ln situ recordings- thesecan be done with modern video and audio technology. But how do we avoidthe problemwith locationof the soundsource, so as not to confusefishes making the soundswith the onesthat just happen to be in the area the cusk-eel weakFishprobiem!,

Evenwhen all the fish are of the same speciesin a tank or in situ,we are often interested in which individual fish produced a given sound. This allows us to relate the size or behavior of the fish to the sound and gives an understandingof what the sooal environment was in which it produced the sound mating behavior,foraging, aggressionetc.!.

One area of great importance in the future is determining the impact of noise pollution in the marineenvironment. If fishesrely on soundfor communication,are the noisesproduced by human activities interfering with the fishes ability to mate, fight, and locate food or predators? We need to do more researchon the impact of fishing gear, boats, pipelines,dredging, petroleum exploration seismic surveys,and military operations on soniferous fishes. Should these be noisesregulated? At what levels?Can the fish hear these sounds?Do they respondto the sounds? McCauleyet al, 002! haveshown that a fish'sability to hearis affectedby prolongedexposure to the soundsproduced by air gunsused in seismicsurveys by geologists.American shad are affectedby echo-sounders usinghigh frequencysounds, which they can hear Mannet al. 1997,Mann et a!. 1998!apparently becausebottleneose dolphins,a shadpredator, also usethese frequencies for echo location. Is spawning interrupted? Bottlenosedolphin disrupt the spawning of silver perch Luczkovichet al. 2000!, but we know little of how echo sounders and fishing vesselnoises affect this speciesand its relativesin the Sciaenidae.Are migrationroutes blocked? For example, American shad migrate upstream to spawn,but turn away at placeswhere underwater gas pipelines crossthe estuary or river,due to the acousticenvironment produced by the rushingfluids and gassesin the pipe Art Popper pers comm.!.

The passiveacoustics approach can providefish biologistsand fishery scientists with a non-destructive sampling tool that can provide a unique perspective of the biology and ecology of soniferous species of fishes.

Literature Cited Aristotle's HistoriaAnimalium,4: 9.Translated by D'A Thompson.Oxford: Clarendon Press,1910.

Casaretto,L. and Hawkins,A.D. 2002. Spawning behavior and the acoustics repertoire of haddock. Bioacoustics 12: 250-252.

Fine,M.L. 1978. Seasonal and geographicalvariation of the matingcall of the oystertoadfish Opsanustau L.Oecologia36:

Fish,Marie Poland,Alton S.Kelsey, Jr., William H. Mowbray,1952. Studies on the Production of Underwater Sound by North Atlantic CoastalFishes. Journal of Marine Research6: 180-193.

Fish,M. P.and W.H. Mowbray.1970. Soundsof Western North Atlantic Fishes,The Johns Hopkins Press. Baltimore. 207 pp.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 177 Hawkins,A.D, and M.C. P. Amorirn. 2000. Spawning sounds of the malehaddock, Melanogrammus aeglefinus. Environ. Biol, Fish, 59: 29-41.

Hawkins,A.D, L. Casaretto, M.Picciulin, K.Olsen. 2002. Locating spawning haddock by meansof sound, Bioacoustics 12: 284-286.

Kaatz,l.M. 2002, Multiple Sound-Producing mechanisms in teleost fishes and hypotheses regarding their behavioural significance.Bioacoustics 12:230-233.

Label,PS. 6 D.A.Mann, 1995. Spawning sounds of thedomino damselfish, Dascyllus a/bise/la Pomacentridae!,andthe relationshipto male size.Bioacoustics6:187-198.

Lobel,P 5.2001.Fish bioacoustics and behavior: passive acoustic detection and the applicationof a closed-circuitrebreather for field study.Marine Technology Society Journal,35:19-28.

Luczkovich,J,J., Sprague, M.W., Johnson, S. Eand Pullinger, R.C. 1999. Delimiting spawning areas of weakfishCynoscion regalis Familiy Sciaenidae! in Parnlico Sound, North Carolina using passive hydroacousticsurveys, Bioacoustics,10, 143-160.

Luczkovich,J.J., H.J. Daniel ill, M. Hutchinson, T Jenkins, S.E.Johnson, R.C. Pullinger and M.W. Sprague.2000. Sounds of sexand death in the sea:bottlenose dolphin whistles suppress mating chorusesof silver perch. Bioacoustics,10, 323-334.

Mann,David A. and Phillip S. Lobel. 1995. Passive Acoustic Detection of SoundsProduced By the Damselfish,Dascyllus. Bioacoustics 6: 199-213.

Mann,David A., and Lobel, Phillip S. 1997. Propagation of damselfish Pomacentridae! courtship sounds.Journal of the AcousticalSociety of America101: 3783-3791.

Mann,David A., Jeanette Bowers-Altman, Rodney A. Rountree. 1997. Sounds Produced by the Striped Cusk-eelOphidion marginatum Ophidiidae!.Copeia 3: 610-612.

Mann,David A., Zhongmin Lu,Arthur N. Popper.1997, A Clupeid Fish Can Detect Ultrasound. Nature 389:341.

Mann,David A., Zhongmin Lu, Mardi C, Hastings, Arthur N.Popper. 1998, Detection of Ultrasonic Tonesand Simulated Dolphin Echolocation Clicks by a Clupeidfish.J. Acoust. Soc. Am. 104: 562-568.

Mann,D.A. and P,S. Lobel. 1998. Acoustic behavior of the darnselfishDascyllus a/bise/la: behavioral and geographic variation, Environ. Biol. Fish. 51: 421-428,

McCauley,R.D., J. Fewtrell, A.J. Duncan, and A. Adhitya. 2002. Behaviroral, physiological and patho- logical responseof fishesto air gun noise.Bioacoustics 12: 318-312.

Myrberg,A.A., Jr. 1972. Ethology of the bicolordamselfish, Eupomacentrus parti tus Pisces: Pomacentridae!:a comparativeanalysis of laboratory and field behavior.Anim. Behav.Mon. 5: 197- 283.

Proceedingsfrom the /nternationai Workshopon the Applications of PassiveAcoustics to Fisheries 178 Myrberg,A.A.,Jr., M. Mohler 8 J.D.Catala, 1986, Sound production by males of a coral reef fish Pomacentruspartitus!: its significanceto females.Anim, Behav.34: 913-923.

Sprague,M. Wand J.J.Luczkovich. 2001. Do striped cusk eels,Ophidion marginatum Ophidiidae! produce the 'chatter'sound attributed to weakfish,Cynoscion regaiis Sciaenidae!?Copeia 2001 !: 854-859.

S prague,M.W., Luczkovich, J,J., Pullinger R.C., Johnson, S.E., Jenkins T., & Daniel,H,J III, 000!. Using spectralanalysis to identify drumming soundsof some North Carolinafishes in the family Sciaenidae. J. Elisha Mitchell Soc. 116!:124-145.

Wood,M., Casaretto, L., G. Horgan, and A. D. Hawkins. 2002, Discriminating between fish sounds- a wavlet approach. Bioacoustics 12:337-339.

Proceedingsfrom the internat'ionai Workshopon the Appiications of PassiveAcoustics to Fisheries 179 David Mann

Universityof SouthFlorida, College of MarineScience. 140 7th Ave,South, St. Petersburg, FL 33701 dmannOmarine.usf.edu

Introduction Thepurpose of thisreport is to summarizethe findings of theTechnology Working Group that was heldon thethird day of theworkshop. The Technology Working Group was tasked with reviewing papers presentedduring the workshop,and information from the literature, and to summarizeour state-of-knowledgeon passiveacoustics applications to fisheriesand the census of marine life. In addition,the groupwas tasked with providingrecommendations on areasof technologydevelop- ment that weredeemed by the participantsto be of highestpriority and most likely to facilitate advancesin the application passiveacoustics to fisheriesissues.

Thesuccess and developmentof fish bioacousticsdepends on high quality recordingsystems and analysissoftware, It isimportant that the technology is matchedto thequestions being asked. This documentprovides an overview of existingtechnologies with the purposeof identifyingtechnolo- gies that can be applied to specific fish bioacousticsquestions. It is not meant as an exhaustivesur- vey of existingacademic and commercialproducts. The main conclusion is that for mostquestions the neededtechnology exists for advancingfish bioacoustics.The main impediments are the level of educationon the use of technologywithin the field and a generalawareness by funding agen- ciesof the greatpotential that studiesof fish bioacousticscan provide to researchstudies on fish and fisheries.This workshop has been a firststep to removingboth of theseimpediments, and for identifying waysto break them down further.

Hydrophones Hydrophonesare the mostbasic element of anyrecording system, They are underwatermicro- phonesthat typically convert sound pressure into an electrical signal that can be recordedby a data acquisitionsystem. There are many commercial suppliers of hydrophonesthat are appropriatefor fish soundrecordings,

Simple Systems Perhapsthe mostimportant technology area identified by participantsare simple systems to record and analyzesounds. Simple recording and analysis systems are useful for recordingfish soundsto

Proceedingsfrom the internationalWorkshop on theApplications of Passive Acoustics to Fisheries 180 identifythe soundsproduced by differentspecies and for performingsurveys of locationsof sound- producing fishes. A simplesystem consists of a hydrophonewith a data acquisition device. Data acquisition systemsinclude audio and digital tape recorders,audio-video recorders Lobel!, and computerswith soundcards. Digital systems provide obvious advantages over analog systems in termsof greaterfrequency bandwidth and dynamicrange, and will be the mostcommonly used systemsin the future.Which system is chosenwill dependon the recordingsituation, Computer systemsthat maybe practicalfor recordingsmade in the laboratory,may not be practicalin a field situation,because of powerand portability issues. One important development is the useof remotelyoperated vehicles ROVs! and permanentunderwater listening stations for monitoring soundproducing fishes Blueand Rountree;Luczkovich and Sprague; Brower and Barans!.These systemswill be importantin characterizingwhich species produce which sounds, especially for speciesthat will be difficultto maintainin a laboratorytank. They will alsoprove useful for docu- rnentingbehavior of fish aggregationswhen multiple fish callsimultaneously,

Severalcaveats of recordingsystems were brought up thatone needsto beaware of including;

1, Data compression:Some recorders suchas mini-disc and MP3! use data compression tech- niquesthat alterthe recordedsound frequency and level.These would not be appropriatefor usein cataloguingknown fish sounds,but couldbe veryuseful for ecologicalsurveys of sound- producing fishes.

2. Automatic Gain Control AGC!:Many systems especiallymany audio tape recorders and video cameras!use automatic gain control to keepthe recordedvolume within the samerange, If a system uses AGC, it will not be possible to determine the received sound level. 3. Bit resolution:Systems that recordwith a higherbit-resolution will havea largerdynamic range the range of the quietest and loudest soundsthat can be recorded!.

One issue that many participants have encountered are problems with boat-induced noise on recordingsystems, either through electrical noise on the boat,or the physicalmovement of the boat causingthe hydrophoneto move.Bungee cords have been successfully used to decoupleboat movementand hydrophonemovement, and acceleration canceling hydrophones are commeroally available.One other technique is to usetelemetry buoys from the ship seebelow!.

Datalog gers Audiodatalog gers are useful for recordingover long periodsof timein manylocations simultaneously, Dataloggersprovide a wayto gatherinformation on the distributionsof sound-producing fish that would not be possibleotherwise without considerableinvestment of human resources.A good example of this are the pop-ups recorders Clark!.

Computersare the bestoption for recordingas an audio datalogger where continuous power is available,such as from shore or on a boat. Commercialsoftware such as Avisoft! existsfor record- ingon a givenduty cycle.However, continuous power is rarely available in field situationswhere onewould like to makerecordings. In thesesituations low-power battery-operated dataloggers are i'eqU ired.

Proceedingsfrom the International Workshopon the Applications of PassiveAcoustics to Fisheries 181 Todate all audiodataloggers that have been used for fishbioacoustics have been engineered by individuallaboratories to performthis task.These include analog tape recordersthat havebeen modifiedto recordon a particularduty cycle Luczkovich!, and digital dataloggers that have been programmedto recordas desired Clark; Mann!. There is no commercially available datalogger that canbe purchased and used directly without either engineering or softwareprogramming usually both!. Thislack of an off-the-shelfproduct has greatly limited their usein fish bioacoustics.

Telemetry Telemetrysystems broadcast a hydrophonesignal to a boator shore-basedreceiver, They perform thesame function as datalog gers in allowingrecordings over a largearea for longperiods of time. Severaltypes of telemetrysystems are available including sonobuoys VHF!, cell phone systems, and short rangemicrowave systems. All of thesesystems require line-of-site between the transmitter andreceiver, and a relativelyhigh-level of engineeringto setupand maintain. Telemetry isalso capableof deliveringvideo to documentbehavior during soundproduction Svredal!.

Satellitesystems generally do notsupport the bandwidth needed for transmitting acoustic data. At this point,some amount of preprocessingwould be required,so that limiteddata on soundcharac- teristics e.g. RMSlevel, frequency spectra!could be transmitted.

Hydrophone Arrays Hydrophonearrays could be usedfor localizingsound producing fishes and for producinga direc- tionalreceiver to improvethe signalto noiseratio Forsythe!.They have been used for determining thelocations of vocalizingwhales in manydifferent situations, but have not yet been applied to fishes Jarvis!, They require a high-levelof sophistication for setting up, operating,and analyzing the data. Hydrophonearrays hold promisein answeringquestions about fish distributionsthat could notbe otherwise obtained with single hydrophone recordings. Most participants recognized the potentialbenefits of hydrophonearrays, and they were one area where further training and descrip- tions of existing systemswould be useful.

Speakers Underwaterspeakers are usefulin conductingplayback experiments to determinethe reactionof fishto differenttypes of sounds.The US Navy rents low-frequency projects e,g. J-9,J-1'l! to research projects,and there arealso commercially available speakers for swimmingpools that canbe usedin researchsituations although these usually do not producegood low-frequency responses below 100or 200Hz!. All of thesespeakers require processing of the signalsto be playedto producean accuratereproduction of a fishsound Hawkins!.That isthey do not havea flatfrequency response. So,one can not merelyplay back a recordedsound and hopeto get a perfectreproduction of it.

Proceedingsfrom the internationaiWorkshop on the ApplicationsoF Passive Acoustics to Fisheries 182 Signal ProcessingSoftware Thereare many commercially available packages for dataacquisition and signal processing. Some suchas MATLAB Mathworks, inc.! have a greatdeal of flexibilityand power,but requirea highlevel of knowledgeof signalprocessing. Others are targeted specifically at bioacousticiansincluding Signal Engineering Design!,Canary Cornell University!,and Avisoft. The manualsto these software programsare often the clearestsource of informationfor learningsignal processing techniques and their applications.

Onearea that wasidentified as an importantarea of researchand developmentare tools for auto- maticidentification of speciesand for analyzinglong datasets. Such tools would dependon the developmentof a libraryof fish sounds Bloomberg!.They would havegreat value in makingpas- sive acoustics accessible to all fisheries researchers.

Education Mostfish bioacousticiansare biologistsfirst andengineers second. This is becausewe havearrived at fish bioacousticsas a powerfulway to studyfishes that no other approachcan provide. This meansthat we haveto pick up engineeringand signal processing principles as we go along. Unfortunately,there is no onegood source of informationabout recording and signal processing that is accessibleand practicalfor the fish bioacoustician,This gap canbe bridgedboth by producing thesetargeted materials and conductingtraining workshops, and by attractingengineers with a biological interest to the field.

Proceedingsfrom the international Workshopon the Applications of PassiveAcoustics to Fisheries 183