Journal Article

Bycatch: complementary information for understanding fish behaviour. Namibian Cape hake (<i>M. capensis</i> and <i>M. paradoxus</i>) as a case study

Ana Gordoa, Heinrich Lesch and Silvia Rodergas

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 63, issue 8, pages 1513-1519
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.2006.05.007
Bycatch: complementary information for understanding fish behaviour. Namibian Cape hake (M. capensis and M. paradoxus) as a case study

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To identify spatio-temporal distribution in Namibian Cape hake (M. paradoxus and M. capensis), incidental hake catch by the horse mackerel fleet and targeted catch by the hake fleet were analysed for the period 1999–2004. The targeted catch, 45 955 fishing days, came from hake fishery logbooks and the incidental catch, 24 689 trawls, from observers' sample data collected aboard vessels of the horse mackerel fleet. A strong negative relationship between monthly catch rates (cpue) and bycatch was observed, confirming that the seasonal change in catchability is caused by differences in hake vertical dispersion. The October trends were an exception: both cpue and bycatch were negative. A drop in catchability at different depths of the fishing grounds indicates that M. capensis migrates to shallower water (<200 m) at the peak of spawning. Although there was no significant relationship between annual catch rates and bycatch, probably because of the short length of the time-series, annual bycatch should not be discarded as an indicator of hake recruitment. The results highlight the potential informative component of bycatch in identifying population patterns that cannot be extracted from the targeted catch.

Keywords: bycatch; catchability; distribution; hake; northern Benguela

Journal Article.  3534 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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