Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): The nighttime scattering layer

Engraulis anchoita is a physostomous fish with a dual chambered swimbladder (sb). In situ target strength (TS) measurements on this species are only possible at night, when anchovies disperse forming a scattering layer near the sea surface. A survey data series comprising more than 50000 single targ...

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Autores principales: Madirolas, A., Membiela, F.A., Gonzalez, J.D., Cabreira, A.G., Dell'Erba, M., Prario, I.S., Blanc, S.
Formato: JOUR
Materias:
depth dependence
Engraulis anchoita
fish target strength
in situ measurements
physostomous fish
TS modelling
Clupeiformes
Engraulidae
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_10543139_v74_n5_p1408_Madirolas
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:paper_10543139_v74_n5_p1408_Madirolas
record_format dspace
spelling todo:paper_10543139_v74_n5_p1408_Madirolas2023-10-03T16:00:44Z Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): The nighttime scattering layer Madirolas, A. Membiela, F.A. Gonzalez, J.D. Cabreira, A.G. Dell'Erba, M. Prario, I.S. Blanc, S. depth dependence Engraulis anchoita fish target strength in situ measurements physostomous fish TS modelling Clupeiformes Engraulidae Engraulis anchoita Engraulis anchoita is a physostomous fish with a dual chambered swimbladder (sb). In situ target strength (TS) measurements on this species are only possible at night, when anchovies disperse forming a scattering layer near the sea surface. A survey data series comprising more than 50000 single target detections, recorded from 1995 to 2008, was analyzed in order to study the species specific TS at 38 kHz. A TS vs. fish total length (L) equation was obtained from the in situ measurements (TS = 31.9 log L - 82.4 dB; r 2 = 0.78). When the slope of the regression line was forced to 20 into the TS equation, the resulting value for the constant term (b 20) was -'68.6 dB. In any case, these results indicate an average difference of +3 dB (higher TS values) when compared with the general model suggested for clupeoid fish. The TS measurements obtained inside the nighttime sound scattering layer exhibited a negative trend with depth. An empirical depth dependence term for the anchovy TS equation was obtained through a three parameter least square fitting of the data [TS = 31.3 log L - 79.6 dB - 4.74 log (1 + z/10); r 2 = 0.74]. Anatomical data obtained through high resolution X-Ray Computed Tomography was employed as input for a Prolate Spheroidal Model (PSM). Theoretical TS vs. tilt angle functions were obtained considering the compression of the sb at different depths and under the assumption of different contraction rates. The TS functions were then averaged over different fish tilt angle distributions and used to derive theoretical depth dependence curves of average fish TS. The implications of the adopted sb contraction rate and tilt angle distribution are discussed by comparing the modelled TS(z) curves against the empirical data. © International Council for the Exploration of the Sea 2016. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_10543139_v74_n5_p1408_Madirolas
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic depth dependence
Engraulis anchoita
fish target strength
in situ measurements
physostomous fish
TS modelling
Clupeiformes
Engraulidae
Engraulis anchoita
spellingShingle depth dependence
Engraulis anchoita
fish target strength
in situ measurements
physostomous fish
TS modelling
Clupeiformes
Engraulidae
Engraulis anchoita
Madirolas, A.
Membiela, F.A.
Gonzalez, J.D.
Cabreira, A.G.
Dell'Erba, M.
Prario, I.S.
Blanc, S.
Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): The nighttime scattering layer
topic_facet depth dependence
Engraulis anchoita
fish target strength
in situ measurements
physostomous fish
TS modelling
Clupeiformes
Engraulidae
Engraulis anchoita
description Engraulis anchoita is a physostomous fish with a dual chambered swimbladder (sb). In situ target strength (TS) measurements on this species are only possible at night, when anchovies disperse forming a scattering layer near the sea surface. A survey data series comprising more than 50000 single target detections, recorded from 1995 to 2008, was analyzed in order to study the species specific TS at 38 kHz. A TS vs. fish total length (L) equation was obtained from the in situ measurements (TS = 31.9 log L - 82.4 dB; r 2 = 0.78). When the slope of the regression line was forced to 20 into the TS equation, the resulting value for the constant term (b 20) was -'68.6 dB. In any case, these results indicate an average difference of +3 dB (higher TS values) when compared with the general model suggested for clupeoid fish. The TS measurements obtained inside the nighttime sound scattering layer exhibited a negative trend with depth. An empirical depth dependence term for the anchovy TS equation was obtained through a three parameter least square fitting of the data [TS = 31.3 log L - 79.6 dB - 4.74 log (1 + z/10); r 2 = 0.74]. Anatomical data obtained through high resolution X-Ray Computed Tomography was employed as input for a Prolate Spheroidal Model (PSM). Theoretical TS vs. tilt angle functions were obtained considering the compression of the sb at different depths and under the assumption of different contraction rates. The TS functions were then averaged over different fish tilt angle distributions and used to derive theoretical depth dependence curves of average fish TS. The implications of the adopted sb contraction rate and tilt angle distribution are discussed by comparing the modelled TS(z) curves against the empirical data. © International Council for the Exploration of the Sea 2016.
format JOUR
author Madirolas, A.
Membiela, F.A.
Gonzalez, J.D.
Cabreira, A.G.
Dell'Erba, M.
Prario, I.S.
Blanc, S.
author_facet Madirolas, A.
Membiela, F.A.
Gonzalez, J.D.
Cabreira, A.G.
Dell'Erba, M.
Prario, I.S.
Blanc, S.
author_sort Madirolas, A.
title Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): The nighttime scattering layer
title_short Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): The nighttime scattering layer
title_full Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): The nighttime scattering layer
title_fullStr Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): The nighttime scattering layer
title_full_unstemmed Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): The nighttime scattering layer
title_sort acoustic target strength (ts) of argentine anchovy (engraulis anchoita): the nighttime scattering layer
url http://hdl.handle.net/20.500.12110/paper_10543139_v74_n5_p1408_Madirolas
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