A method for controlled target strength measurements of pelagic fish, with application to European anchovy (Engraulis encrasicolus)

Doray, Mathieu; Berger, Laurent; Bouffant, Naig Le; Coail, Jean Yves; Vacherot, Jean-Philippe; Bernardie, Xavier de la; Morinière, P.; Lys, Elisabeth; Schwab, Romain; Petitgas, Pierre

doi:10.1093/icesjms/fsw084

Cited by 6 publications

(3 citation statements)

References 25 publications

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“…Nonetheless, it could be necessary to supplement [42]’s model with a gaseous cylinder model (e.g. [56]) when GB organism backscattering dominates the entire frequency spectrum.…”

Section: Discussionmentioning

confidence: 99%

Characterization of sound scattering layers in the Bay of Biscay using broadband acoustics, nets and video

et al. 2019

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Sound scattering layers (SSLs) are observed over a broad range of spatio-temporal scales and geographical areas. SSLs represent a large biomass, likely involved in the biological carbon pump and the structure of marine trophic webs. Yet, the taxonomic composition remains largely unknown for many SSLs. To investigate the challenges of SSL sampling, we performed a survey in a small study area in the Northern Bay of Biscay (France) by combining broadband and narrowband acoustics, net sampling, imagery and video recordings. In order to identify organisms contributing to the observed SSLs, we compared measured frequency spectra to forward predicted spectra derived from biological data. Furthermore, to assess the confidence in SSL characterization, we evaluated uncertainties in modeling, acoustical and biological samplings. Here, we demonstrate for the first time that SSL backscattering intensity in the Bay of Biscay can be dominated in springtime by resonant gas bearing organisms below 100 kHz, namely siphonophores and juvenile fishes and by pteropods at higher frequencies. Thus, we demonstrate the importance of broadband acoustics combined to nets, imagery and video to characterize resonant backscatterers and mixed mesozooplankton assemblages.

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“…Nonetheless, it could be necessary to supplement [42]’s model with a gaseous cylinder model (e.g. [56]) when GB organism backscattering dominates the entire frequency spectrum.…”

Section: Discussionmentioning

confidence: 99%

Characterization of sound scattering layers in the Bay of Biscay using broadband acoustics, nets and video

et al. 2019

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“…These two angles are not necessarily equivalent. During echo-tracking, the SONAR 5 calculates the swimming angle, or more specically, the mean aspect angle (or pitch angle [28]). The aspect angle is dened by the sh angle between the tracked ping i and i+1 on the vertical axis [20].…”

Section: Angle Determinationmentioning

confidence: 99%

“…With dz i , dx i and dy i the target displacement between the ping i and the ping i+1, in each dimension [20,28].…”

Section: Aspect Anglementioning

confidence: 99%

Effect of a Transducer Horizontality Default on Lake Fish Stock Assessment

et al. 2020

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reshwater hydroacoustic surveys are frequently performed with small research boats. Thus, the transducer, usually fixed on a pole on the side of the boat, could be misaligned with the horizontal axis (i.e., the lake surface). Given that fish acoustic responses are strongly directional, the transducer angle could induce attenuation of their backscattering strengths. To test the influence of a small shift of the transducer orientation, we compared hydroacoustics estimates from two sampling nights on the Lake Annecy: the first one being a transducer angle of 1.5∘ with the horizontal and the second one being strictly horizontal. We showed that the effect of such an angle is negligible over the sampling variability on the TS distribution of the fish population and the biomass assessment. We conclude that a small shift in the transducer horizontality (≤1.5∘) will not degrade the quality of the acoustic data.

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The PELGAS survey: Ship-based integrated monitoring of the Bay of Biscay pelagic ecosystem

Doray

Petitgas

Romagnan

et al. 2018

Progress in Oceanography

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The Pélagiques Gascogne (PELGAS) integrated survey has been developed by a multidisciplinary team of Ifremer and La Rochelle University scientists since 2000, joined by commercial fishermen in 2007. Its initial focus was to assess the biomass and predict the recruitment success of anchovy in the Bay of Biscay in spring. Taking advantage of the space and versatility of R/V Thalassa II, sampling has been progressively extended to other ecosystem components. PELGAS therefore further developed the second objective of monitoring and studying the dynamic and diverse Biscay pelagic ecosystem in springtime. The PELGAS survey model has allowed for the establishment of a long-term time-series of spatially-explicit data of the Bay of Biscay pelagic ecosystem since the year 2000. Main sampled components of the targeted ecosystem are: hydrology, phytoplankton, mesozooplankton, fish and megafauna. The survey now provides two main ecosystem products: standard raster maps of ecosystem parameters, and a time series dataset of indicators of the Bay of Biscay pelagic ecosystem state. They are used to inform fish stock and ecosystem-based management, and support ecosystem research. The present paper introduces the PELGAS survey, as a practical example of an integrated, vessel-based, ecosystem survey. The evolution of the PELGAS scientific team and sampling protocols are presented and analysed, to outline factors crucial to the success of the survey. Data and results derived from PELGAS are reviewed, to exemplify scientific questions that can be tackled by integrated ecosystem survey data. Advantages and challenges of the survey are discussed and put into the context of marine ecosystem surveys in the European Marine Strategy Framework Directive and the Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. Common Fisheries Policy. Highlights ► The PELGAS integrated survey conducted since 2000 in spring in the Bay of Biscay is presented. ► PELGAS objectives have switched from the study of the anchovy stock status to ecosystem monitoring. ► Spatially-explicit data have been collected of the main pelagic ecosystem components since 2000. ► Multidisciplinary collaborative working and enough vessel space were critical success factors. ► Finding relevant common scales is essential to analyse ecosystem data within or across compartments.

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A method for controlled target strength measurements of pelagic fish, with application to European anchovy (Engraulis encrasicolus)

Cited by 6 publications

References 25 publications

Characterization of sound scattering layers in the Bay of Biscay using broadband acoustics, nets and video

Characterization of sound scattering layers in the Bay of Biscay using broadband acoustics, nets and video

Effect of a Transducer Horizontality Default on Lake Fish Stock Assessment

The PELGAS survey: Ship-based integrated monitoring of the Bay of Biscay pelagic ecosystem

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