Observing incidental harbour porpoise Phocoena phocoena bycatch by remote electronic monitoring

Abstract

Quantification of marine mammal bycatch is important in the context of conservation and management of protected species. Hitherto, using on-board observers has been the most reli- able and accurate method; however, observer programs can be prohibitively expensive. To inves- tigate the potential of closed-circuit television cameras to document bycatch of marine mammals, 6 Danish commercial gillnetters (10 to15 m in length) operating under the Danish catch quota management system were equipped with remote electronic monitoring (REM) systems. The REM systems provided video footage, time and position of all net hauls and bycatches of marine mam- mals. Comparisons between REM results and fishers' logbooks showed that the REM system gave more reliable results, since fishers, in many cases, did not observe the bycatch while working on the deck because the bycatch had already dropped out of the net before coming on board. Fur- thermore, very high coverage percentages at low cost, compared to on-board observers, could be obtained with REM. Alternative means of conducting the video analysis were tested; they were, however, not found to be very efficient.