© 2006 International Council for the Exploration of the Sea
Bycatch: complementary information for understanding fish behaviour. Namibian Cape hake (M. capensis and M. paradoxus) as a case study
a Centro de Estudios Avanzados de Blanes (CSIC) Acc. Cala Sant. Francesc 14, 17300 Blanes (Girona), Spain
b Hangana Seafood (Pty) Ltd, Ben Amathila Avenue PO Box 26, Walvis Bay, Namibia
*Correspondence to A. Gordoa: tel: +34 972 336101; fax: +34 972 337806. e-mail: Gordoa{at}ceab.csic.es.
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
Received 3 March 2006; accepted 24 May 2006.