Journal Article

Evidence of a variable “unsampled” pelagic fish biomass in shallow water (<20 m): the case of the Gulf of Lion

P. Brehmer, J. Guillard, Y. Guennégan, J.L. Bigot and B. Liorzou

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 63, issue 3, pages 444-451
Published in print January 2006 | ISSN: 1054-3139
Published online January 2006 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2005.10.016
Evidence of a variable “unsampled” pelagic fish biomass in shallow water (<20 m): the case of the Gulf of Lion

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Studies of small pelagic fish biomass are limited by the fact that research vessels and fishing boats are usually restricted to working areas with a bottom depth >20 m. Consequently, “unsampled” areas can represent a large proportion of the continental shelf, and the biomass in those areas can be important and must be taken into account in assessment methods in order to avoid misleading interpretations in population dynamics. A time-series ten years long has been compiled from acoustic-assessment surveys of small pelagic fish stocks, and the results show an overall increase in the acoustic fish density towards the coast, where values were the highest. Additional experiments on transects covering shallow-water areas (5–20 m) were conducted from 2001 to 2003 with small boats and a research vessel to evaluate the acoustic fish density in those areas. The results confirmed that the fish biomass in shallow water is significant, sometimes very large, and should be evaluated to avoid underestimation. Therefore, surveys should be conducted in shallow water, if at all possible, as well as at greater depths when carrying out surveys destined to support assessment exercises.

Keywords: assessment; hydroacoustic methods; shallow water; small pelagic fish; spatial distribution

Journal Article.  4194 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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