A new in-situ method to estimate fish target strength reveals high variability in broadband measurements

Acknowledgements The authors thank the Greenland Institute of Natural Resources (GINR), the University of Aberdeen, and Marine Alliance for Science and Technology for Scotland (MASTS) for funding this study. MASTS is funded by the Scottish Funding Council (grant no. HR09011) and contributing institutions. Further, they thank GINR for providing access to their facilities.Peer reviewedPublisher PD

Report of the working group on fisheries acoustics science and technology (WGFAST)

The Working Group on Fisheries Acoustics Science and Technology (WGFAST) met at the Food and Agricultural Organisation of the United Nations in Rome, Italy, from 19–22 April 2005. David A. Demer, USA, was Chair, Alex De Robertis, USA, was Rapporteur and Jessica D. Lipsky, USA, was the Recorder. There were 83 participants from 16 countries. a ) The first topic was “Measuring underwater radiated noise from survey vessels and its effects on fish”. Quiet vessels have distinct advantages over conventional vessels. It has been shown that herring did not respond to a vessel which com-plies with the ICES Cooperative Research Report No. 209 specification for radi-ated noise. Reductions in high frequency vessel noise have also increased acous-tic detection ranges for fish and zooplankton. However, it is clear that some spe-cies, under some circumstances, avoid even quiet survey vessels. Thus, a variety of stimuli produced by vessels such as light and particle motion, as well as radi-ated noise, may cause fish to react to a survey vessel. Noise reduced vessels pro-vide new opportunities to investigate these stimuli. WGFAST recommends that research in this area should proceed swiftly and focus on: i) determining which species of fish react to conventional and quiet survey vessels and under what cir-cumstances; ii) the stimuli for their behaviours; and iii) the design requirements for vessels surveying these species in sensitive situations. Additionally, for cases in which fish avoidance is inescapable, survey biases should be estimated. Devel-opment of economical and portable noise measurement systems is also encour-aged. b ) The second topic was “Technologies for remote species identification (low-frequency, Doppler, multi-frequency, broad bandwidth, data integration, optical sensors)”. Species identification can be one of the major sources of uncertainty in acoustic surveys of fish and zooplankton abundance, and it is vital to multi-species and ecosystem studies. Substantial progress was reported on a variety of methods for remote species identification. Such methods enable more automated and objective data processing, reduced uncertainty in acoustic estimates of fish biomass, economical ecosystem investigations and studies of predator-prey inter-actions, and may also facilitate a reduction of by-catch during commercial fishing operations. It was noted that further progress towards species identification will likely require a combination of acoustic and other measurements. Because net sampling is typically used to identify acoustic scatterers, gear selectivity can add substantial uncertainty to acoustic surveys. Thus, the WGFAST encourages re-search on random and systematic error in net sampling, and development of new methods for verifying acoustic scatterers. Particularly promising are underwater stereo video instrumentation and analysis methods. c ) The third topic was “Alternative technologies (small-craft, buoys, ROV, AUV, gliders, fishing vessels, multi-beam sonar, acoustic cameras), with special atten-tion to shallow water and near boundary assessments (coastal, riverine, demersal and epipelagic species, and bottom typing)”. Measurement platforms other than research vessels are being used to economically make measurements on ecologi-cally important temporal and spatial scales. For example, acoustic instruments are being deployed on buoys, landers, autonomous underwater vehicles, remotely op-erated vehicles, and fishing vessels. Expanded use of these platforms is impera-tive for successful ecosystem-based fisheries management. Progress was also re-ported on development of multi-beam sonars, and analyses of their data for bio-mass estimation. Finally, productive collaborations between commercial manu-facturers and the scientific community were reported and encouraged. d ) The fourth topic was “Target strength (modelling and measurements)”. There is a growing body of evidence indicating that a first-order approximation of TS ver-sus log-length is generally insufficient to accurately and precisely estimate fish TS. It was shown that factors such as fish orientation (tilt, roll, and yaw), age-dependent changes in morphology, and region-dependent relations between fish mass, length, and swimbladder volumes can eclipse the effect of fish length on their TS. Exemplifying this point was another study showing a bimodal TS distri-bution from herring characterized with a unimodal length distribution. e ) WGFAST recommends that it next meets at CSIRO in Hobart, Tasmania, on 27, 28, 29, and 30 March, 2006 to examine works in the following research areas: i) Fish behaviour in response to noise and other vessel related stimuli; ii) Survey techniques for epi-benthic, epi-pelagic and shallow water species; iii) Acoustical species ID techniques for multi-species assessments, ecosystem studies, by-catch reduction, and objective and automated data processing; iv) Instrumentation, survey design, and data analysis techniques for studying aquatic ecosystems, with special attention to the estimation and use of meas-urement uncertainty in statistical analyses of multi-variate time series, and techniques for integrating multi-disciplinary data to elucidate functional rela-tionships; and v) Target strength (modelling and measurements). f ) WGFAST recommends that SGASC and SGTSEB both be extended for another year, retaining their current Chairs, to complete their respective CRRs; and SGAFV and SGASC also meet in Hobart on 25–26 March, and 31 March-2 April, respectively. g ) WGFAST recommends research on: 1) noise and other vessel related stimuli for fish behaviour; 2) video and still camera instrumentation and data processing; and 3) instrumentation and methods for remote species identification. These topics should be considered for one or more new Study Group at the 2006 meeting. h ) WGFAST and WGFTFB jointly recommend that a Task Force be formed, lead by David Somerton, USA, to: evaluate the state-of-the-art in optical imaging and analysis technologies and define the ICES community’s requirements for addi-tional optical technology. i ) WGFAST recommends a review of the ecosystem-based fisheries management strategies developed and employed over the past two decades by international communities such as CCAMLR. Accordingly, one or more keynote speakers from CCAMLR and or CSIRO will be invited to the 2006 WGFAST meeting. j ) WGFAST recommends that the ICES sponsored “2008 Symposium on Fisheries Acoustics and Technology for Aquatic Ecosystem Investigations,” is held from in June 2008 at Grieg Hall, Bergen, Norway. k ) WGFAST Recommends the following theme sessions for the 2006 Annual Sci-ence Conference: i) Joint FTC-RMC Theme Session on “Quantifying, summariz-ing and integrating total uncertainty in fisheries resource surveys.” Co-Conveners: David Demer, U.S.A.; and Stephen Smith, Canada; ii) Joint FTC/LRC Theme Session on “Spatio-temporal characteristics of fish populations and their environmental forcing functions as components of ecosystem-based as-sessments.” Co-Conveners: François Gerlotto (France), and someone from LRC; and iii) Joint FTC/LRC Theme Session on “Technologies for monitoring fishing activities and observing catch.” Co-Conveners: Bill Karp, USA, and Kjell Nedre-aas, Norway

Report of the Working Group on Fisheries Acoustic Science & Technology (WGFAST) [18–22 May 2009 Ancona, Italy]

Contributors: Lucio Calise, Nils Håkansson, Rolf Korneliussen, Hector Peña and Eirik Tenninge

Report of the working group on fisheries acoustics science and technology (WGFAST)

Contributors: John Dalen, Olav Rune Godø, Nils Olav Handegård, Hans Petter Knudsen, Egil Ona, Ruben Patel, Geir edersen, Atle TotlandThe Working Group on Fisheries Acoustics Science and Technology (WGFAST) met at the Food and Agricultural Organisation of the United Nations in Rome, Italy, from 19–22 April 2005. David A. Demer, USA, was Chair, Alex De Robertis, USA, was Rapporteur and Jessica D. Lipsky, USA, was the Recorder. There were 83 participants from 16 countries. a ) The first topic was “Measuring underwater radiated noise from survey vessels and its effects on fish”. Quiet vessels have distinct advantages over conventional vessels. It has been shown that herring did not respond to a vessel which com-plies with the ICES Cooperative Research Report No. 209 specification for radi-ated noise. Reductions in high frequency vessel noise have also increased acous-tic detection ranges for fish and zooplankton. However, it is clear that some spe-cies, under some circumstances, avoid even quiet survey vessels. Thus, a variety of stimuli produced by vessels such as light and particle motion, as well as radi-ated noise, may cause fish to react to a survey vessel. Noise reduced vessels pro-vide new opportunities to investigate these stimuli. WGFAST recommends that research in this area should proceed swiftly and focus on: i) determining which species of fish react to conventional and quiet survey vessels and under what cir-cumstances; ii) the stimuli for their behaviours; and iii) the design requirements for vessels surveying these species in sensitive situations. Additionally, for cases in which fish avoidance is inescapable, survey biases should be estimated. Devel-opment of economical and portable noise measurement systems is also encour-aged. b ) The second topic was “Technologies for remote species identification (low-frequency, Doppler, multi-frequency, broad bandwidth, data integration, optical sensors)”. Species identification can be one of the major sources of uncertainty in acoustic surveys of fish and zooplankton abundance, and it is vital to multi-species and ecosystem studies. Substantial progress was reported on a variety of methods for remote species identification. Such methods enable more automated and objective data processing, reduced uncertainty in acoustic estimates of fish biomass, economical ecosystem investigations and studies of predator-prey inter-actions, and may also facilitate a reduction of by-catch during commercial fishing operations. It was noted that further progress towards species identification will likely require a combination of acoustic and other measurements. Because net sampling is typically used to identify acoustic scatterers, gear selectivity can add substantial uncertainty to acoustic surveys. Thus, the WGFAST encourages re-search on random and systematic error in net sampling, and development of new methods for verifying acoustic scatterers. Particularly promising are underwater stereo video instrumentation and analysis methods. c ) The third topic was “Alternative technologies (small-craft, buoys, ROV, AUV, gliders, fishing vessels, multi-beam sonar, acoustic cameras), with special atten-tion to shallow water and near boundary assessments (coastal, riverine, demersal and epipelagic species, and bottom typing)”. Measurement platforms other than research vessels are being used to economically make measurements on ecologi-cally important temporal and spatial scales. For example, acoustic instruments are being deployed on buoys, landers, autonomous underwater vehicles, remotely op-erated vehicles, and fishing vessels. Expanded use of these platforms is impera-tive for successful ecosystem-based fisheries management. Progress was also re-ported on development of multi-beam sonars, and analyses of their data for bio-mass estimation. Finally, productive collaborations between commercial manu-facturers and the scientific community were reported and encouraged. d ) The fourth topic was “Target strength (modelling and measurements)”. There is a growing body of evidence indicating that a first-order approximation of TS ver-sus log-length is generally insufficient to accurately and precisely estimate fish TS. It was shown that factors such as fish orientation (tilt, roll, and yaw), age-dependent changes in morphology, and region-dependent relations between fish mass, length, and swimbladder volumes can eclipse the effect of fish length on their TS. Exemplifying this point was another study showing a bimodal TS distri-bution from herring characterized with a unimodal length distribution. e ) WGFAST recommends that it next meets at CSIRO in Hobart, Tasmania, on 27, 28, 29, and 30 March, 2006 to examine works in the following research areas: i) Fish behaviour in response to noise and other vessel related stimuli; ii) Survey techniques for epi-benthic, epi-pelagic and shallow water species; iii) Acoustical species ID techniques for multi-species assessments, ecosystem studies, by-catch reduction, and objective and automated data processing; iv) Instrumentation, survey design, and data analysis techniques for studying aquatic ecosystems, with special attention to the estimation and use of meas-urement uncertainty in statistical analyses of multi-variate time series, and techniques for integrating multi-disciplinary data to elucidate functional rela-tionships; and v) Target strength (modelling and measurements). f ) WGFAST recommends that SGASC and SGTSEB both be extended for another year, retaining their current Chairs, to complete their respective CRRs; and SGAFV and SGASC also meet in Hobart on 25–26 March, and 31 March-2 April, respectively. g ) WGFAST recommends research on: 1) noise and other vessel related stimuli for fish behaviour; 2) video and still camera instrumentation and data processing; and 3) instrumentation and methods for remote species identification. These topics should be considered for one or more new Study Group at the 2006 meeting. h ) WGFAST and WGFTFB jointly recommend that a Task Force be formed, lead by David Somerton, USA, to: evaluate the state-of-the-art in optical imaging and analysis technologies and define the ICES community’s requirements for addi-tional optical technology. i ) WGFAST recommends a review of the ecosystem-based fisheries management strategies developed and employed over the past two decades by international communities such as CCAMLR. Accordingly, one or more keynote speakers from CCAMLR and or CSIRO will be invited to the 2006 WGFAST meeting. j ) WGFAST recommends that the ICES sponsored “2008 Symposium on Fisheries Acoustics and Technology for Aquatic Ecosystem Investigations,” is held from in June 2008 at Grieg Hall, Bergen, Norway. k ) WGFAST Recommends the following theme sessions for the 2006 Annual Sci-ence Conference: i) Joint FTC-RMC Theme Session on “Quantifying, summariz-ing and integrating total uncertainty in fisheries resource surveys.” Co-Conveners: David Demer, U.S.A.; and Stephen Smith, Canada; ii) Joint FTC/LRC Theme Session on “Spatio-temporal characteristics of fish populations and their environmental forcing functions as components of ecosystem-based as-sessments.” Co-Conveners: François Gerlotto (France), and someone from LRC; and iii) Joint FTC/LRC Theme Session on “Technologies for monitoring fishing activities and observing catch.” Co-Conveners: Bill Karp, USA, and Kjell Nedre-aas, Norway

Amplitude and phase sonar calibration and the use of target phase for enhanced acoustic target characterisation

This thesis investigates the incorporation of target phase into sonar signal processing, for enhanced information in the context of acoustical oceanography. A sonar system phase calibration method, which includes both the amplitude and phase response is proposed. The technique is an extension of the widespread standard-target sonar calibration method, based on the use of metallic spheres as standard targets. Frequency domain data processing is used, with target phase measured as a phase angle difference between two frequency components. This approach minimizes the impact of range uncertainties in the calibration process. Calibration accuracy is examined by comparison to theoretical full-wave modal solutions. The system complex response is obtained for an operating frequency of 50 to 150 kHz, and sources of ambiguity are examined. The calibrated broadband sonar system is then used to study the complex scattering of objects important for the modelling of marine organism echoes, such as elastic spheres, fluid-filled shells, cylinders and prolate spheroids. Underlying echo formation mechanisms and their interaction are explored. Phase-sensitive sonar systems could be important for the acquisition of increased levels of information, crucial for the development of automated species identification. Studies of sonar system phase calibration and complex scattering from fundamental shapes are necessary in order to incorporate this type of fully-coherent processing into scientific acoustic instruments

Acoustic detection of the Greenland shark (Somniosus microcephalus) using multifrequency split beam echosounder in Svalbard waters

The conservation status of the long-lived Greenland shark (Somniosus microcephalus) is unknown, and methods for non-invasively estimating local or regional abundances are wanted. Using a multifrequency split beam echosounder during long line fishery for Greenland sharks, we demonstrate how individual sharks can be identified and separated with high accuracy from the acoustic backscattering at three frequencies. From a slowly drifting vessel, hooked and free-swimming targets with similar target characteristics were identified on echograms along the bottom and in the water column over a depth of ∼ 400 m. A discriminate analysis using target frequency response, target strength and echo pulse stretching was used to identify shark targets from the only possible competitor, with respect to target strength, being large Atlantic cod (Gadus morhua). Isolation and tracking of single targets allowed us to calculate the swimming speeds ranging between 0.16 and 0.84 m s−1 (mean ± SD, 0.47 ± 0.18 m s−1) from 15 free-swimming sharks over distances from 11 and 50 m in time periods of 28 to 122 s per track. Our findings demonstrate the first acoustic detection of Greenland sharks, and thus provide a new non-invasive monitoring method applicable in otherwise difficult-to-access arctic and deep-sea waters.publishedVersio