A recent study published in the journal PLOS One revealed that dolphins are being killed in trawler fishing operations at an alarming rate of one a week in Australia’s North West.
According to the article on the Business Insider, the study, Patterns of Dolphin Bycatch in a North-Western Australian Trawl Fishery, conducted by researchers from Murdoch University and the North Carolina State University, found that minimum of 500 bottlenose dolphins have been incidentally caught in the Pilbara Trawl Fishery in the last decade.
The bycatch of small cetaceans in commercial fisheries is a global wildlife management problem.
The scientists that conducted the study used data from captains’ logbooks and independent observers provided by the Department of Fisheries and stored in a Microsoft Access database to learn more about bottlenose dolphin (Tursiops truncatus) bycatch patterns between 2003 and 2009 in the Pilbara Trawl Fishery, Western Australia.
According to Murdoch University’s Cetacean Research Centre, the data gathered from captains’ logbooks showed that dolphin bycatch rates have not dropped since 2006 when bycatch reduction devices were introduced across the fishery.
The Department of Fisheries conducted trials of trawl nets equipped with active and inactive pingers and monitored by underwater video cameras to alert marine mammals to the presence of fishing gear and/or deter them from approaching fishing gear and aquaculture operations, which yielded no differences in the number of dolphins swimming into the nets.
Pinger trials were subsequently abandoned in favour of the compulsory introduction of BRDs across the fishery. The Department of Fisheries have subsequently commenced another trial of larger, louder pingers in the PTF, but results are yet to be reported. Pingers have been shown to reduce the bycatch of some cetaceans, including harbour porpoises (P. phocoena), Franciscana dolphins (Pontoporia blainvillei) and common dolphins. However, they do not elicit consistent responses in all small cetacean species, nor do they have the same affects across all types of fisheries.
The study proposed that trawlers install top-opening escape hatches from which dolphins might escape to the surface to further reduce dolphin bycatch.