Status of dolphin bycatch mitigation in the Pilbara trawl fishery
Protected and listed species including dolphins, turtles and critically endangered sawfish are incidentally caught (as ‘bycatch’) in varying numbers the Pilbara Fish Trawl Interim Managed Fishery each year.
May 2012 marks two years since submission of the report “Reducing Dolphin Bycatch in the Pilbara Finfish Trawl Fishery” (download here) to the Fisheries Research and Development Corporation, Western Australian Dept of Fisheries and Nickol Bay Professional Fishers Association. Here, we summarise the main findings and recommendations from the report.
Grey nurse shark caught as bycatch
Summary of findings:
Analyses of independent observer records provided by the Dept of Fisheries indicated that dolphin bycatch rates were 1.6 to 3.5 times higher than those reported in skippers logbooks. Further analyses of the observer data showed that:
(a) Dolphin capture rates varied between vessels (one vessel caught more dolphins than others);
(b) Dolphin capture rates did not vary between management areas or seasons, but varied between times of day (dolphin catch rates were lowest between midnight and 6 am);
(c) Dolphin capture rates were lower after the placement of Bycatch Reduction Devices (BRDs – consisting of an exclusion grid and a bottom-opening escape hatch) in the trawl nets in 2006.
However, underwater video footage taken from inside trawl nets showed bycatch falling out of the escape hatch before being landed on deck. This indicates that bycatch is under-estimated by both skippers and observers.
Guitarfish caught as bycatch
Recommendations from this research:
(1) Conduct a six-month trial of trawl nets with BRDs fitted with top-opening escape hatches from which air-breathing animals (dolphins and turtles) can escape;
(2) Implement a dedicated independent observer program, including onboard observers and under-water video footage collection, to evaluate the efficacy of the new nets;
(3) Retention, rather than immediate discard of dolphin carcasses, for measurements and sample collection by qualified personnel.
Progress in early 2012:
Despite unanimous agreement by the Dept. of Fisheries, industry and researchers to commence these trials and the associated observer program in late 2010 (download here), none of these recommendations have yet been adopted.
The number of dolphins reported captured in the Dept of Fisheries’ State of the Fisheries Reports in 2008, 2009 and 2010 was 17, 19 and 17, respectively. However, the actual number of dolphins being caught in this fishery each year is likely to be much higher. Actual dolphin capture rates will remain unknown until the recommendations from the report are adopted.
Unfortunately, the sustainability of this fishery and the ongoing viability of the dolphin population cannot be assumed.
