Reducing accidental mortality of dolphins

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RESEARCH AREA
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This week’s featured research article has just been published in Marine Policy by SARDI researchers and examines code of practice for reducing accidental mortality of dolphins in purse-seine net fisheries in South Australia. The total number of dolphins accidentally killed in the world’s purse-seine fisheries may be substantial, even if interaction rates are generally low. This paper describes an industry Code of Practice (CoP) that was established in Australian purse-seine fishery after an observer program detected high dolphin interaction rates that had not been reported in fishery logbooks. Key features of the CoP are search and delay procedures designed to prevent encirclements and release procedures that minimise mortalities. Extrapolation from observer data (3.9% of net sets observed), suggested that 449 dolphin encirclements and 423 mortalities occurred in 2004-05, the year before the CoP was established. A decade later, observer data suggest that annual encirclements and mortalities had been reduced by 87% and 97%, respectively. Searches were highly effective in detecting the presence of dolphins. Dolphins were not encircled in > 85% of net-sets made after searches determined that dolphins were absent from the fishing area. Opening the front of the net resulted in the successful release of all dolphins in > 86% of encirclement events. Discrepancies between interaction rates estimated from observer data and those recorded in logbooks have decreased over time. The researchers state that this study demonstrates that codes of practice that specify changes in fisher behaviour can be effective in mitigating the interactions of purse-seine fisheries with dolphins. The paper concludes that the avoidance and release procedures documented in the CoP for the South Australian sardine fishery are simple and, if adopted in other purse-seine fisheries, could substantially reduce global mortality of dolphins. The article can be downloaded here (or email jennie.fluin@sa.gov.au for a copy).