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ICES Journal of Marine Science: Journal du Conseil Advance Access originally published online on May 8, 2009
ICES Journal of Marine Science: Journal du Conseil 2009 66(6):1155-1161; doi:10.1093/icesjms/fsp113
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© 2009 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

This article appears in the following ICES Journal of Marine Science issue: The Ecosystem Approach with Fisheries Acoustics and Complementary Technologies [View the issue table of contents]

A method for reducing uncertainty in estimates of fish-school frequency response using data from multifrequency and multibeam echosounders

Laurent Berger1, Cyrille Poncelet1 and Verena M. Trenkel2

1 Ifremer, Département NSE, Centre de Brest, Z. I. Pointe du Diable, BP 70, 29280 Plouzané, France
2 Ifremer, Département EMH, rue de l’Ile d’Yeu, BP 21105, 44311 Nantes Cedex 03, France

Correspondence to L. Berger: tel: +33 298224700; fax: +33 240374075; e-mail: laurent.berger{at}ifremer.fr.

Berger, L., Poncelet, C., and Trenkel, V. M. 2009. A method for reducing uncertainty in estimates of fish-school frequency response using data from multifrequency and multibeam echosounders. – ICES Journal of Marine Science, 66: 1155–1161.

Fish schools can be insonified simultaneously with multifrequency echosounders (e.g. Simrad EK60s) and a multibeam echosounder (e.g. Simrad ME70). This paper presents a method for combining these data to improve estimates of the relative frequency response r(f) of fish schools. Values of r(f) are now commonly used to classify echoes in fishery surveys. The data from the roll- and pitch-stabilized, high-resolution ME70 are used to correct beam-width effects in the multifrequency EK60 data. First, knowing the exact position and orientation of the transducers and the position of the vessel, the echoes are placed into a common geographic coordinate system. Then, the EK60 data are rejected if they do not include a significant percentage of the fish school imaged with the multibeam echosounder. Echoes that exceed the overlap threshold are used to estimate the r(f). The proposed method is applied to simulated and actual data for sardine and mackerel schools in the Bay of Biscay to estimate their r(f) values. The results for different overlap thresholds are compared with the results of a different method, one that uses adaptive thresholds on volume-backscattering strength Sv. The proposed method reduces uncertainty in estimates of r(f) for schools with an overlap of greater than 80%, and it outperforms the Sv-thresholding technique.

Keywords: acoustics, pelagic fish, Sardina pilchardus, Scomber scombrus, species identification

Received 8 August 2008; accepted 11 February 2009; advance access publication 8 May 2009.


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