The Incidental Catch of Dolphins in Gillnet Fisheries in Zanzibar, Tanzania

The level of incidental catches of dolphins in artisanal gillnet fisheries was investigated in a questionnaire survey of 101 gillnet vessel operators from 10 villages in Unguja island of Zanzibar, representing half of all the gillnet fishing fleet in 1999. A total of 96 dolphins were reported to have been incidentally caught between 1995 and 1999; 43 Indo-Pacific bottlenose dolphins (Tursiops aduncus), 29 spinner dolphins (Stenella longirostris), 5 IndoPacific humpback dolphins (Sousa chinensis) and 19 unidentified dolphins. Most of these incidental catches (46) were reported in 1999. We extrapolate that 93 animals may have been incidentally caught by the entire fishing fleet (201 vessels) during 1999. This estimate represents a serious cause for concern, suggesting that the incidental capture of dolphins in Zanzibar’s artisanal gillnet fisheries may be high enough as to have a significant negative impact on local populations. Further studies to accurately estimate the total bycatch, as well as the abundance of dolphin populations in the area are essential to assessing the biological significance of these incidental catches. However, management efforts should be implemented immediately to reduce the number of dolphins killed in these fisheries.