Journal Article

Different surveys provide similar pictures of trends in a marine fish community but not of individual fish populations

Verena M. Trenkel, John K. Pinnegar, Marie-Joëlle Rochet and Brian D. Rackham

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 61, issue 3, pages 351-362
Published in print January 2004 | ISSN: 1054-3139
Published online January 2004 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2004.01.004
Different surveys provide similar pictures of trends in a marine fish community but not of individual fish populations

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Choice of sampling method and survey period can have an important impact on the perception of the structure and dynamics of an ecological community. For the Celtic Sea fish assemblage we compared data obtained by three different trawl surveys: an autumn groundfish survey with a GOV trawl, and a spring and an autumn groundfish survey, both carried out with a Portuguese high-headline trawl. Time-series of abundance estimates were not consistent among surveys for all species and were generally very noisy. An analysis of variance components showed that the sampling method contributed more to the variance in abundance estimates compared to survey period, interannual variability, or even sampling variance. Overall community assessments based on indicators such as proportions of non-commercial and piscivorous species, and the proportion of benthic species showed similar trends for all data series. The shape of the size spectrum based on abundances per length class summed over all fish species, although stable over time, was highly sensitive to the sampling method. With the exception of size spectra, community indicators for marine fish assemblages monitored by surveys seem to be robust to survey period and trawling gear, but species abundance trends are method dependent.

Keywords: abundance; Celtic Sea; size spectrum; species diversity; survey; trawl

Journal Article.  5866 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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