An International Workshop on the Application of Passive Acoustics in Fisheries
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Photo of Donald BaltzSpotted seatrout Spawning Requirements & Essential Fish Habitat: A Microhabitat Approach Using Hydrophones Return to Top

Donald M Baltz (Coastal Fisheries Institute & DOCS, Louisiana State University)

A microhabitat approach using hydrophones to identify important activities can yield a fish's eye view of its habitat requirements. At the finest scale, the microhabitat of an individual is the site it occupies at a point in time. Site selection presumably optimizes net energy gain but is controlled in combination by physiological constraints, prey distributions, foraging success, competitor densities, and predation pressures. Because individuals select similar microhabitats, many independent measurements and associated environmental variables define a population's responses to environmental gradients. Spawning site variables include temporal, spatial, and microhabitat data: depth, distance from shore, substrate, turbidity, salinity, temperature, DO, current velocities, and some measure of spawning aggregation size. Habitat Suitability is an index of Use/Availability that ranges from zero (intolerable) to one (optimal). Resource Use is a probability statement, given the presence of spawning, and Resource Availability is a probability statement, regardless of the presence of spawning: Suitability=P(E|F)/P(E). Previous research on spawning spotted seatrout in Louisiana identified points that were selected and avoided along salinity, depth, substrate, and velocity gradients. Relatively deep, moving waters with salinities of 14-23 and temperatures of 29-33 C were selected. Spawning sites shifted with the salinity gradient, indicating that environmental conditions were more important than location fidelity. Sound Intensity (db re 1 micro pascal) may be used to estimate Source Level, after correcting for one-way spreading loss (i.e., 20 log [depth in meters]), if distance to the spawning aggregation is known and provides a continuous-variable estimate of aggregation size for statistical modeling.

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Photo of Carol BloomgardenCreating a Web-based Library of Underwater Biological Sounds
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Jack W. Bradbury and Carol A.Bloomgarden* (Macaulay Library of Natural Sounds, Cornell Laboratory of Ornithology)

Establishing an archive of fish and other underwater biological sounds will meet many of the long-standing challenges faced by marine acousticians - the restoration and preservation of their recordings, easy access to the sounds for analysis, and the storage of hundreds of hours of passive recordings in a digital format. Researchers will be able to annotate their sounds through an online database application, summarize search results in exportable tables and maps, and download copies of recordings for research, teaching, and conservation. The MLNS is committed to dual goals of maintaining open access to allow other researchers to listen and help identify sounds, while protecting recordists' copyrights and restricting access during the publication process. Detailed and extensive metadata are needed, however, to create the functionality such an archive requires.

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Photo of Joseph BlueUse of ROVs as a platform for passive acoustics: characterization of ROV noise generation Return to Top

Rodney Rountree (UMass-Dartmouth), Joseph E. Blue* (Leviathan Legacy, Inc. ) and Francis Juanes (UMass-Amherst)

The use of passive acoustics for tracking was developed for naval warfare during and before WW II. A passive acoustics tracking system was implemented on torpedoes for homing on ships and submarines. This system will be discussed along with its limitations for homing on soniferous fish when mounted on Remotely Operated Vehicles (ROVs). This system was developed before the advent of small, fast computers and was implemented with electronics that are now known as operational amplifiers. The theory of these analog systems will be discussed along with digital methods that now can make computer implementations of this type of system and modifications of it feasible for implementation on ROVs. Adequate Signal-to-Noise ratios are require for implementing these techniques. Reaction of fish to a ROV during Stellwegen Bank dives will be shown as that may present a problem in attempting to get good data from some types of fish. Noise from ROV thrusters using 3 hydrophones configure to track soniferous fish was measured during dives on the Stellwegen Bank. The ROV employed was too noisy for getting good signatures from most fish. The noise measurements are to be presented. Some types of loud fish that may be detected above the ROV noise are discussed.


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Photo of Myra BrouwerPotential for coupling of underwater TV monitoring with passive acoustics Return to Top

Charles A. Barans and Myra C. Brouwer* (South Carolina Marine Resources Research Institute)

The temporally and spatially fluid nature of fish associations often confuses interpretations of their underwater sounds. Ideally, visual confirmation of the sound producers and any behaviors associated with sound making should complement acoustic data. The South Carolina Marine Resources Division (MRD) established an artificial reef structure and underwater television (UWTV) system for monitoring reef fishes at a site approximately 72 km off Georgia. Transmission of digital image data was from a bottom-mounted camera system via an established microwave linkage to shore. This study was part of the South Atlantic Bight Synoptic Offshore Observational Network (SABSOON) project, a collaborative effort to study oceanographic conditions and fisheries resources that inhabit continental shelf waters. The long-term goal of this research is to evaluate UWTV for providing fishery managers real-time data on reef fish assemblages to establish and/or modify management regulations. Underwater observations were conducted daily for a year and a half. We documented a variety of vertebrate and invertebrate species associated with seasonal temperatures changes. The identification of fish species has been difficult to sort out with acoustic records in complex and highly diverse environments such as natural and artificial reefs. As with some hydroacoustic records, small fish were not easily identified with UWTV, especially if more than one species was present. Although many of the presently known sonic signatures have been corroborated with visual observations, many more are needed to assist in interpretations from randomly placed hydrophones, especially in complex habitats with many interacting species of vertebrates and invertebrates.

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Photo of Chris ClarkApplication of passive acoustic methods for automatic detection, location and tracking of whales
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Christopher W. Clark (Cornell University)

All baleen whales produce species specific sounds and at least five species produce long, patterned, hierarchically organized sequences of sounds referred to as songs. Baleen whale distribution and relative abundance estimates are traditionally based on visual surveys from vessels and/or airplanes. This approach is limited by visibility conditions and access to observation platforms. Acoustic monitoring using either single or multiple sensors offers a significant improvement by increasing spatial and temporal sampling. Signal processing techniques allow automatic detection, location and tracking. Throughout the last 20 years acoustic hardware and software tools have been developed and applied to survey whale species and gain insights into natural behaviors. This includes the use of Navy SOSUS arrays to detect and estimate numbers of vocal animals by species throughout an ocean basin, autonomous seafloor sensors to detect, locate and track species of interest in regions, and sparse or towed hydrophone arrays to detect, locate and track species of interest in specific study areas. For at least four species, SOSUS data reveal annual seasonal and large geographic fluctuations reflecting migration, feeding and breeding patterns. For bowheads combined visual-acoustic efforts have lead to calculation of a robust population assessment and trend over a 20-year period, as well as understandings of acoustic functions. For blue and fin whales, passive acoustics in combination with visual, biopsy, Photo-ID, and prey field surveys is beginning to reveal details of vocal function, details that are critical for interpreting and evaluating acoustic data alone.

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Photo of Mark CollinsLocating sciaenid spawning aggregations in anticipation of harbor modifications, and reactions of spotted sea trout spawners to acoustic disturbance Return to Top

Mark R.Collins* (Marine Resources Research Institute, South Carolina Dept. of Natural Resources), Bridget Callahan, Bill Post and Amanda Avildsen (SCDRN)

Estuarine-dependent sciaenids are the most economically important fishes in the Savannah River (SC/GA, USA) estuary. Plans for major modifications and deepening of the Savannah Harbor and shipping channel have generated special concerns about exacerbating sciaenid spawning stock reductions through interference with spawning aggregations. A passive acoustic survey designed to define the geographic and temporal distribution of spawning aggregations of the most important sciaenid species, determine site fidelity between years, characterize spawning habitats, and determine effects of dredging activity on aggregations was therefore conducted during 2000-2001. Of the economically important sciaenids encountered, six primary spawning sites were identified for spotted seatrout, one for weakfish, and one for black drum. No large red drum spawning aggregations were located, but individuals or small groups of drumming males were found. Sites for all species were in salinities > 16 ppt, and all were within 12.2 river km of the river mouth. Time of day of spawning appeared to be anchored around sunset with peak activity from about 1 hr before through about 3 hr after. There was considerable seasonal overlap in spawning activity among species, and in the lower 2 river km there appeared to be spatial overlap. However, on a finer scale (hundreds of meters) there was little or no overlap. Spotted seatrout and red drum ignored ships and dredging but ceased drumming when bottlenose dolphin passed by. Because two (and possibly three) of the species appear to aggregate around structures, removal of these structures during deepening and channelization operations may have a negative impact.

 

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Photo of Martin ConnaughtonCharacterization of sounds and their use in two sciaenid species: weakfish and Atlantic croaker
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Martin A Connaughton*(Washington College), Michael L. Lunn (Phildelphia College of Osteopathic Medicine), Micheal L. Fine (Department of Biology, Virginia Commonwealth University) and Malcolm H. Taylor, (College of Marine Studies and Department of Biological Sciences, University of Delaware)

Weakfish, Cynoscion regalis, and Atlantic croaker, Micropogonias undulatus, produce sound with bilaterally paired, extrinsic sonic muscles. In weakfish, only the male bears sonic muscles and produces sound: staccato bursts of 6-10 individual pulses at a repetition rate of 23.3 pulses per second (pps) at 21-23ÉC. Field recordings from Delaware Bay indicated that sound production was highly seasonal and coincided with the spawning season, and was most intense in the evening, the time of greatest spawning activity. Identical sounds were recorded during captive spawning trials, where sound production ceased prior to gamete release, which was apparently synchronized by body contact. The number of bursts per minute produced by a given male remained relatively constant during the course of an evening, regardless of the proximity of a spawning event. In Atlantic croaker, both males and females bear sonic muscles and will produce fright response sounds. However, in preliminary captive spawning trials, only the male produced courtship sounds. Croaker sounds consist of a smaller number of pulses per burst, 1-9 in fright response sounds and 1-3 in courtship sounds. The repetition rate for fright response sounds was much higher (30pps) than for courtship sounds (5.4pps). Dominant frequency of fright response sounds decreased with length (650-450Hz for 23-30cm fish at 21ÉC), and though only one fish was recorded during captive spawning trials, it appears that the frequency of these calls is much lower than those of fright response sounds (300Hz for a 32.5cm fish).

 

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Photo of David DemerDetection and characterization of yellowfin and bluefin tuna using passive acoustical techniques
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Scott Allen (University of New Hampshire, Center for Ocean Engineering) and David Demer* (NMFS / Southwest Fisheries Science Center, La Jolla, CA )

Underwater sounds generated by Thunnus albacares and Thunnus thynnus were recorded and studied to explore the possibility of passive-acoustical detection. Tuna vocalizations were recorded at the Monterey Bay Aquarium, Monterey, California, and Maricultura del Norte in Ensensada, Baja California, Mexico. At both locations, the most prevalent sounds associated with tuna were low-frequency pulses varying from 20 to 130 Hz, lasting about 0.1 seconds, and usually single and unanswered. A behavior similar to coughing was coincident with these sounds: the animal's mouth opened wide with its jaw bones extended and its abdomen expanded, then contracted abruptly. On one occasion in Mexico, this behavior and associated noise were simultaneously recorded. The center frequencies of these vocalizations may vary as the resonant frequencies of the tuna's swim bladder, suggesting a passive-acoustical proxy for measuring the size of tuna. Matched-filter and phase-difference techniques were explored as means for automating the detection and bearing-estimation processes.

Passive- and active-acoustical monitoring of marine life using multi-instrumented buoys Return to Top

David Demer* (NMFS/Southwest Fisheries Science Center, La Jolla, CA ), Derek Needham, (Sea Technologies Services, Cape Town, South Africa), and Stephane Conti (Southwest Fisheries Science Center)
For over a decade, the Antarctic Treaty's Committee for the Conservation of Antarctic Marine Living Resources has pioneered the ecosystem approach to fisheries management. In support of this effort, the U.S. Antarctic Marine Living Resources Program investigates responses of krill predators to changes in the availability of their food. One challenge of this investigation is to temporally and spatially match observations of predators and their prey. Towards this end, the Advanced Survey Technologies Program at Southwest Fisheries Science Center has developed multi-instrumented, remotely-monitored, light-weight, low-cost buoys to provide long time-series measurements of krill availability and predator activities in the near-shore area of Cape Shirreff, Livingston Island, Antarctica. Prototype buoys have recently been deployed with a 300 kHz acoustic Doppler current profiler to measure currents, volume backscatter, water temperature, pitch, roll, and bearing; and 38 and 200 kHz echosounders. Passive-acoustical detection and bearing estimation systems have also been developed and tested for integration into the buoys. Additionally, the buoys include a computer, GPS, radar reflector, strobe, radio-modem, and power management circuit. Remote control of the instrumentation and real-time monitoring of data is accomplished by radio-telemetry between the buoy and a distant land-station. Thus, a safe and cost-effective method has been developed for remotely monitoring the presence of vocalizing whales and seals in harsh environments, as well as characterizing the variability in the prey available to them and their oceanographic habitat. The first deployments in February 2002 have garnered new information about the temporal variations in krill dispersion and possible environmental forcing.


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Photo of Mike FineAcoustic competition in the gulf toadfish Opsanus beta: Crepuscular changes and acoustic tagging
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Michael L. Fine* (Virginia Commonwealth University)
and Robert F. Thorson

Nesting male gulf toadfish Opsanus beta produce a boatwhistle advertisement call used in male-male competition and to attract females and an agonistic grunt call. The grunt is a short-duration pulsatile call, and the boatwhistle is a complex call typically consisting of zero to three introductory grunts, a long tonal boop note and zero to three shorter boops. The beginning of the boop note is also gruntlike. Anomalous boatwhistles contain a short duration grunt embedded in the tonal portion of the boop or between an introductory grunt and the boop. Embedded grunts have sound pressure levels and frequency spectra that correspond with those of recognized neighbors, suggesting that one fish is grunting during another's call, a phenomenon here termed acoustic tagging. Snaps of nearby pistol shrimp may also be tagged, and chains of tags involving more than two fish occur. The stimulus to tag is a relatively intense sound with a rapid rise time, and tags are generally produced within 100 ms of a trigger stimulus. Time between the trigger and the tag decreases with increased trigger amplitude. Tagging is distinct from increased calling in response to natural calls or stimulatory playbacks since calls rarely overlap other calls or playbacks. Tagging is not generally reciprocal between fish suggesting parallels to dominance displays.


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Photo of Steve ForsytheMultihydrophone localization of low frequency broadband sources Return to Top

Steve Forsythe
(NUWC Newport)

In theory, one can use multiple hydrophones distributed in space to localize a source position/direction: using time-of-flight differences among the hydrophones, generate multiple hyperboloids then solve for the surfaces' intersection to give a unique position for the source, perhaps in the least-squares sense. In practice, this is difficult for low frequency signals generated by fish (thumps, etc.) because the onsets of the signals are not well defined. By using cross correlations among the received signals as a "fuzzy" measure of time difference it is possible to do the equivalent of the intersecting hyperboloids calculation with an uncertain measure of time differences, giving the equivalent of a probability density of source location over a predetermined space of a priori possible locations.


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Photo of Susan FudgePassive Acoustic Field Research on Atlantic Cod, Gadus morhua L. in Canada
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Susan Fudge* and George A. Rose (Memorial University of Newfoundland)

Passive acoustics is a relatively new field of research in Newfoundland and Canada. The vanguard work has been on Atlantic cod (Gadus morhua) and in particular on spawning behaviour. Cod spawn in large aggregations with sexually diverse behaviours. Males appear to hold the spawning location while females come and go (batch spawners). Sonar tagging has shown that some cod return to the same spawning grounds in subsequent years. Atlantic cod are known to exhibit differences in spawning behaviours among sub-stocks and to have distinct spawning behaviours among ages and sexes. The importance of the social behaviour of cod during spawning is important not only to fisheries production but also to conservation and management. That cod produce and detect sound during spawning has long been recognized from lab experiments. However, ours is the first attempt in Canada to document the sounds made during spawning at sea and to relate these to spawning behaviour. A working hypothesis is that male sounds are characteristic of spawning aggregations and assist in group identification and membership. Our study encompasses two of the largest spawning components of cod in Newfoundland waters. Preliminary results are presented to illustrate recorded sounds of spawning cod.

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Photo of Grant GilmorePassive acoustic transects: Mating calls and spawning ecology in East Florida sciaenids
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Grant Gilmore (Dynamic Corp. Kennedy Space Center)

Experimental explorations in nocturnal fish call distributions were first made in 1976 in the Indian River Lagoon in East Florida. This eventually developed into a systematic survey of estuarine fish calls with a post doctoral fellow, Hin Kiu Mok at the Harbor Branch Oceanographic Foundation. All sciaenid calls were identified to species within a survey region and correlated with egg/larval abundance. Sound attenuation experiments were also conducted to allow accurate isolation of call aggregation sites. This resulted in a publication (Mok and Gilmore 1983) describing sciaenid calls in the black drum, Pogonias cromis, silver perch, Bairdiella chrysoura, and spotted seatrout, Cynoscion nebulosus. Acoustic studies of these sciaenid populations continued increasing in intensity with a multi-disciplinary study of the spotted seatrout from 1990 to1994. Neural networks were developed to allow computer software to identify specific fish sounds, as well as detailed hydrological studies of spawning sites, larval ecology and juvenile settlement patterns. Remote recording devices were designed and deployed which allowed up to one week of preprogrammed ambient sound recordings on digital recorders. Spawning site distribution was mapped in detail using acoustic transects which allowed a model of spawning site choice to be developed. These studies continue with most work taking place in the northern Indian River Lagoon system, including the Mosquito Lagoon, a protected estuary. Presently NASA is supporting the development and deployment of passive acoustic technologies to monitor aquatic acoustic organisms within the protected waters of the Kennedy Space Center.

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Photo of Tony HawkinsThe use of passive acoustics to identify a haddock spawning area
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Tony Hawkins (FRS Marine Laboratory, Aberdeen, Scotland)

The codfish family (Gadidae) contains several vocal species. One of them is the haddock, Melanogrammus aeglefinus, a common food fish of the North Atlantic The haddock produces a range of sounds in different contexts. During courtship and spawning, a succession of sounds are produced by males ranging from short series of slowly repeated 'knocks' to longer sounds where the knocks are repeated very rapidly. Wavelet analysis has been used to define the characteristics of haddock sounds and even to discriminate between sounds from different individuals.

Haddock are currently fished beyond safe biological limits. Their spawning grounds may be closed to fishing in the future to limit damage. Haddock are believed to spawn offshore, but reports also suggest that spawning may take place inshore. A search for spawning haddock was carried out in coastal waters using passive listening to detect their characteristic sounds. By this means an aggregation of spawning fish was located in a subarctic Norwegian fjord. Sound production was most intense at night, with the calls of many fish overlapping to give a rumbling sound. Spawning appeared to take place on the seabed, with the males spaced out in a matrix of territories. Repeat surveys showed that the spawning concentrations occurred in the same location over two successive years.

The wider use of passive listening, and the application of techniques like wavelet analysis which allow unambiguous identification, may greatly assist in the search for the spawning areas of commercially important food fishes.

 

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Photo of Scott HoltUsing a towed acoustic array to survey drum spawning sites in the Gulf of Mexico
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Scott Holt (University of Texas Marine Science Institute)

A towed hydrophone array was used to survey for red drum (Sciaenops ocellatus) spawning sites along central Texas coast in the western Gulf of Mexico. The array is composed of an eight-element array in an 80 meter cable and a 200m towing cable. The array was towed at approximately 3.5 kts. from a 105 foot stern trawler during the known spawning time (both season and daily) of red drum. Red drum produce a characteristic drumming or knocking sound during courtship and spawning. Although the pulse pattern of the call is variable, the fundamental frequency is consistently around 140-160 Hz. The occurrence of red drum spawning activity was determined by listening to the tapes for characteristic sounds and by examination of spectral analysis of the data stream. We estimated that clearly identifiable calls of individual red drum could be heard over a distance of 80-100m and convergent sounds of numerous red drum over greater but undetermined distances. Individual red drum were heard regularly along the tow track but were seldom heard in close proximity to each other. Although more drumming activity was heard in the vicinity of tidal inlets, drumming occurred over a relatively wide area of the shallow coastal waters. The temporal nature of spawning activity (red drum only spawn during a few hours in the evening) and our limited knowledge of the exact reproductive strategies of red drum make data interpretation somewhat problematic.

 

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Photo of Susan Jarvis
Passive detection and localization of transient signals from marine mammals using widely spaced bottom mounted hydrophones in open ocean environments
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Susan Jarvis* and David Moretti (Naval Undersea Warfare Center Division Newport)

The Navy undersea acoustic ranges such as the Atlantic Undersea Test and Evaluation Center (AUTEC) provide broadly spaced hydrophone arrays that are traditionally used to track undersea and surface vehicles which have been equipped with acoustic pingers. Increasingly, this broad infrastructure is being applied to non-traditional tracking problems. The Marine Mammal Monitoring on Navy Undersea Ranges (M3R) program, funded by the Office of Naval Research, is working to develop tools to detect and track marine mammals. The initial development is taking place at AUTEC where a total of 79 broad-band hydrophones are deployed. Passive acoustic data is recorded and used in the development of marine mammal detection and tracking algorithms. This presentation describes the detection and tracking algorithms currently under development for the M3R passive acoustic system and the complementary visual sighting information collected by the AUTEC marine mammal environmental compliance program.

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Photo of Phil LobelFish courtship and mating sounds

Phillip Lobel (Boston University)
This presentation will show the sonic behavior of several coral reef fishes and freshwater cichlids. The emphasis will be on courtship and reproductive sounds, which are amenable to monitoring by passive acoustic detection. Recordings were made in the field using an underwater video camera coupled to a hydrophone for synchronous audio-video recording of behavior.

 

 

Synchronized underwater audio-video recording

Phillip Lobel (Boston University)

This presentation will review my experience trying to record fishes underwater using a video-hydrophone system and other gear.

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Photo of Joe LuczkovichUse of passive acoustics to identify essential fish habitats in North Carolina
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Joseph J. Luczkovich* ( Department of Biology/Institute for Coastal and Marine Resources, East Carolina University) and Mark W. Sprague (Department of Physics, East Carolina University)

Sounds produced by spawning fishes in Pamlico Sound have been recorded both under captive conditions and in field surveys. Sonobuoys and hydrophone passive acoustic surveys, ground-truthed by means of the captive recordings, showed the timing and location of spawning sites for four species in the family Sciaenidae: red drum (Sciaenops ocellatus), spotted seatrout (Cynoscion nebulosus), weakfish (Cynoscion regalis), and silver perch (Bairdiella chrysoura). The calls are produced by males and are species-specific, suggesting that the calls are used for advertisement to attract females. Using the UNCW/NURC Phantom S2 ROV with a calibrated hydrophone, we have videotaped silver perch during their mating period, simultaneously recorded their calls, and measured the sound pressure level (SPL) of an individual near the hydrophone. The sounds were detected first in the early evening, but increased in loudness after dark (SPL reaching 136 dB re 1 mPa). The SPL of the spawning choruses are correlated with egg production, suggesting that the passive acoustic method can be used to estimate fish abundance. Other species were identified in the surveys, including toadfish (Opsanus tau), striped cuskeel (Ophididon marginatum), snapping shrimp (Alpheus sp.), and bottlenose dolphin (Tursiops truncatus). These passive acoustics surveys revealed interesting behavioral interactions as well, with spotted seatrout and weakfish apparently competing for spawning sites, and silver perch showing ?acoustic avoidance? of bottlenose dolphins. These passive acoustic surveys in Pamlico Sound have proven the feasibility of determining critical spawning habitats of sciaenid fishes, and have revealed interesting insights into the biology of these species as well.

 

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Photo of David MannNew technologies for passive acoustic detection of fish sound production
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David Mann (University of South Florida)

I will describe progress in developing instrumentation for passive acoustic detection of fish sounds. Early attempts at passive acoustic detection involved developing a largely analog system that would detect sounds that were above some background level and storing the time of occurrence and sound duration (actual sound data were not stored). From these data, the rate of sound production of different species' sounds could be determined. Recent digital systems use many of the same techniques to detect sounds, but can also store more information such as a time stamp and an actual sound recording segment. I will present data on fish sound production using new passive digital signal processing dataloggers produced by Tucker-Davis Technologies. These dataloggers are very flexible in how signals are detected and processed. These dataloggers represent the next step in developing systems for fisheries bioacoustics.Ultimately fisheries bioacoustics should move the way of fisheries acoustics where the signal output is not the actual sound data, but the locations and intensity of fish spawning.


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Photo of Jarle NordeideIs acoustic calls a premating reproductive barrier between two north-east Atlantic cod (Gadus morhua) groups? A Review
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Jarle Tryti Nordeide* (Bodø Regional University, Norway) and Jens LossFinstad (Department of Fisheries and Marin Biology, University of Bergen, Norway )

This study examines the hypothesis that spawning calls of a migratory and a stationary species of Atlantic cod (Gadus morhua), which are sympatric during the spawning season, is a premating reproductive barrier. Firstly, a hushed hubbub was recorded at a major spawning ground during spawning. Secondly, harmonic frequency and duration of calls from cod kept in tanks varied a lot between individual cod, from 42 to 79 Hz and from 0.11 to 1.25 s, respectively. Having passed the two first obstacles the hypothesis has so far failed to pass the third hindrance. No difference has yet been found in mean harmonic frequency of grunts from stationary (55.7 Hz) and migratory (53.4 Hz) cod, in mean duration of their calls (stationary: 0.33 s, migratory: 0.31 s), nor in multivariate analysis of their oscillograms. However, these analytic tools are rather rough and further analysis are required before final conclusions are drawn.

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Photo of Jan OverdalA remote-controlled instrument platform for fish behaviour studies and sound monitoring Return to Top

Bjørn Totland, Ingvald Svellingen
, and Jan Tore Øvredal* (Institute of Marine Research, Fish Capture Division, Norway)

In order to allow fish sounds to be recorded in situ, a new remote-controlled instrument platform was developed. The platform consists of two main units; an underwater electronics bottle capable of operating at a depth of 500 m, and a surface radio telemetry buoy. The underwater unit houses a single-board computer for sound recording, controlling I/O to various instrument functions and logging data from environmental sensors. The set-up in the underwater unit can easily be modified to provide support for the instrumentation needed for a wide range of behavioural studies. The unit is fitted with several sub-sea connectors on its front lid for video cameras, pan/tilt unit, hydrophones, artificial light, echo-sounder, etc., making it suitable for a variety of experiments. A cable connects the underwater unit to the surface buoy. The buoy contains a video transmitter and a full-duplex 115 kbps UHF data link that enables the instrument platform to be operated from a base-station at a distance of up to two nautical miles with video transfer, and up to 10 miles with data-link only. The platform has been successfully used to record fish sounds in combination with video observations. The advantages of a remote-controlled instrument platform over a system with long cables have been clearly demonstrated in these studies.

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Photo of William RoumillatApplications of underwater acoustics data in fisheries management for spotted seatrout, Cynoscion nebulosus, in estuaries of South Carolina Return to Top

William A.Roumillat*, Myra C.Brouwer (South Carolina Marine Resources Research Institute)

We have collected information on the spawning behavior of spotted seatrout in coastal South Carolina since 1990. Spotted seatrout exhibit group-synchronous development and indeterminate fecundity; that is, gametes are released in batches and total fecundity is not fixed prior to the onset of the spawning season. During the summer, male spotted seatrout produce "drumming" sounds that are related to spawning behavior. By listening to these sounds using hydrophone equipment, we determined the locations, seasonality and diurnal periodicity of spawning aggregations in Charleston Harbor. Behavior patterns based on acoustic data enabled us to target females in imminent spawning condition, then carry out oocyte counts for batch fecundity (BF) estimation. Additional random sampling provided data to estimate spawning frequency (SF) for each of the three dominant year-classes (ages 1-3) in our waters. Ultimately, our annual fecundity (AF) estimates for each age class will faciilitate management of this species in South Carolina. BF varied significantly among year-classes. Female length, weight (ovary-free) and age explained 69%, 68% and 59% of the variability in BF, respectively. Monthly SF varied over the season for each age class. We summed the products of mean monthly BF and corresponding monthly SF to arrive at AF estimates of 3.2, 9.5 and 17.6 million oocytes for age classes 1-3, respectively. Age explained 98% of the variability in AF. These ages contributed an average of 25%, 34% and 19% to the overall reproductive effort during a season. Based on predicted AF values, ages 4 and 5 each contributed about 11%.

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Photo of Rodney RountreeSoniferous fishes of Massachusetts Return to Top

Rodney Rountree* (University of Massachusetts-Dartmouth) and Francis Juanes (University of Massachusetts-Amherst)

There is increasing interest in the potential of passive acoustics as a tool to study temporal and spatial distribution patterns, habitat use, spawning, feeding, and predator avoidance behaviors of fishes. For some fishes it is possible to identify spawning habitats and spawning times simply by listening to underwater sounds. We have begun a field survey of vocal fishes in Massachusetts's waters. One of our early findings is that the striped cusk-eel, Ophidion marginatum, formally thought to occur from New York to Florida, is in fact widely distributed on Cape Cod. In this talk we will present our preliminary findings, demonstrate the sounds of area fishes and describe techniques for conducting low-budget passive acoustic surveys.

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Photo of Sherrylyn RoweMating behaviour of Atlantic Cod (Gadus morhua) Return to Top

Sherrylynn Rowe* and Jeffrey A. Hutchings (Department of Biology, Dalhousie University))

The pattern of matings between individuals in a population, including the number of simultaneous mates and the permanence of pair bonds, is known as the mating system. Within all mating systems, mate choice, intrasexual competition, and sperm competition may lead to variation in mating success among individuals and thus sexual selection. Knowledge of the patterns and processes of mating may be critical to understanding population dynamics. Despite being of theoretical interest and practical importance, the mating system of Atlantic cod Gadus morhua is poorly known; to date, only two studies have documented cod spawning behaviour. As well as demonstrating complex mating patterns, these studies have suggested the occurrence of behavioural and acoustic displays by males, mate choice by females, and alternative reproductive strategies among males. However, there is no information on the selective causes and consequences of these behaviours, nor the structure of the mating system. Our research employs a quantitative approach to understand causes and consequences of variation in the mating system of Atlantic cod at the individual and population levels. We are incorporating both detailed experimental studies in the laboratory and observations of cod in the wild.

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Photo of Henrik SchmidtAcoustic sensing with autonomous ocean sampling networks Return to Top

Henrik Schmidt (Massachusetts Institute of Technology)

The rapidly emerging Autonomous Underwater Vehicle (AUV) technology has the potential of dramatically improving the capabilities for accurate and reliable forecasting of the physical and biological ocean environment. Thus, the multi-AUV Autonomous Ocean Sampling Network (AOSN) adds to the traditional measurement resources a rapidly deployable measurement capability which can be adaptively focused in a specific geographical area. Combined with new coupled physical and biological modeling and data assimilation frameworks, the AOSN has lead to the develoment of new ocean observation paradigms such as LOOPS (Littoral Ocean Observation and Prediction System) for environmental assessment. Even though acoustics is crucial to the navigation and communication within the AOSN and active sonars are the most important sensors for seabed mapping, acoustic sensing of the ocean volume has not yet been adequately developed to be suitable within the AOSN framework. On the other hand, the AUVs have been proven as excellent passive acoustic platforms, e.g. as bi-static receivers for bottom surveys, and the AOSN may therefore have potential as a tool for passive acoustic imaging of schools of vocal fish. Here the LOOPS and AOSN concepts are described, and state-of-the-art in acoustic sensing using AUVs is reviewed, and the potential of this new technology for fish stock assessment is discussed.

 

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Photo of Mark SpagueQuantifying Species-Specific Contributions to the Overall Sound Level Return to Top

Mark W. Sprague (Department of Physics, East Carolina University) and Joseph J. Luczkovich (Department of Biology/Institute for Coastal Marine Resources, East Carolina University)

The sound pressure level of an individual or an aggregation can be used to estimate distance to an individual or the size of the aggregation. When several sources are present, the sound pressure level depends on the number of individuals calling as well as the distribution of the sources. When a sound is over 10 dB greater than the background, the background contribution to the total sound pressure level is negligible. A simple correction factor may be subtracted from the total sound level to obtain levels for sounds 3--10 dB above the background. For short duration sounds, the total sound pressure level of a short time segment in which the sound dominates can be used. Contributions due to long-duration sounds--such as fish aggregations--can be obtained by summing frequency bands of the power spectrum over which the desired source is dominant. This spectral band level is an indicator of the loudness of the sound of interest and, thereby, an indicator of other properties on which the loudness depends. Spectral band levels for spawning aggregations of weakfish Cynoscion regalis and silver perch Bairdiella chrysoura correlate with species-specific egg samples taken at the same time and location. Also, spectral band levels of silver perch can be used to determine their reactions to bottlenose dolphin Tursiops truncatus whistles. When more than one source contributes to a spectral band, possible techniques include short time-windowed spectral bands or wavelet filters that reduce contributions of the unwanted source.

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Photo of Kevin WongThe application of passive acoustics to assess, monitor, and protect the coral reef ecosystems of the U.S. Pacific Islands Return to Top

Russell E. Brainard (NOAA Fisheries - Honolulu Laboratory), Kevin B. Wong*(NOAA Fisheries - Honolulu Laboratory), Joseph J. Luczkovich (East Carolina University), and Mark W. Sprague (East Carolina University)

The programs and activities of the NOAA Fisheries Honolulu Laboratory's Coral Reef Ecosystem Investigation (CREI) are presented and areas where the application of passive acoustic methods may significantly contribute to scientific, management, and operational objectives are highlighted. A call for additional collaborators to help undertake some of this work is put forth. In addressing the two fundamental themes of The National Action Plan to Conserve Coral Reefs, to understand coral reef ecosystems and reduce adverse human impacts, the CREI was established to assess, monitor, map, restore, and protect the coral reef ecosystems of the U.S. Pacific Islands. CREI activities include rapid ecological assessments of fish, corals, algae and invertebrates, towed diver digital video habitat and fish surveys, acoustic seabed classification surveys, towed video and still camera surveys, and in-situ and satellite remote sensing observations of oceanographic conditions. The in-situ oceanographic observations include closely spaced conductivity-temperature-depth-chlorophyll casts, acoustic Doppler current profiler surveys, long-term moored oceanographic buoys, surface velocity drifters, and APEX diurnally migrating profiling drifters. While the oceanographic moorings and satellite remote sensing allow high temporal resolution monitoring of the physical processes driving these ecosystems, the remoteness of these ecosystems prevents adequate temporal monitoring of the biological responses (surveys can only be conducted at 1-2 year intervals). We propose to develop passive acoustic techniques to monitor some aspects of the health of these remote ecosystems and to develop warning systems to alert scientists and resource managers of large changes or potential threats. Passive acoustic techniques are also proposed to monitor vessel traffic and illegal incursion into marine protected areas.

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Photo of Mark WoodClassifying fish sounds using wavelets Return to Top

Mark Wood (Dept. of Mathematical Sciences, Univ. of Aberdeen)

Wavelets have become increasingly popular since the 1980's, when rapid developments were made in giving the subject a formal mathematical framework. They have been applied in many different fields including signal and image processing, speech recognition, physics and engineering. Wavelets provide a set of time and scale varying basis functions for representing signals, very often extracting more information than the familiar Fourier transform.

This talk considers the problem of discriminating between fish sounds to automatically recognise individual fish and different species of fish. Properties of the discrete wavelet transform are used to remove noise and isolate individual sounds. The stationary wavelet transform is then used to derive features for discrimination. Results from experiments to classify individual haddock and separate different species of fish will be presented.

This work enables biologists to relate sound production with fish behaviour through simultaneous video recordings, and the method may also provide a non-invasive technique for locating fish spawning grounds in the sea.

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