Tests of visual cues and sub-surface nets as bycatch mitigation measures in small-scale gillnet fisheries in Peru

Citation
Mangel JC, Alfaro-Shigueto J, Wang J, et al (2014) Tests of visual cues and sub-surface nets as bycatch mitigation measures in small-scale gillnet fisheries in Peru. ACAP Seabird Bycatch Working Group, Punta del Este, Uruguay
Abstract

This report summarizes results of two experiments of potential fisheries bycatch mitigation techniques aimed at reducing captures of seabirds, sea turtles and other non-target species in gillnet fisheries in Peru. The first experiment used light emitting diodes (LEDs) to illuminate the length of a gillnet to determine if net illumination could serve as a visual alert and effectively reduce capture of seabirds and other protected species. In the second experiment, a standard surface driftnet was modified to float just under the ocean surface (as compared to at the sea surface) to determine if this modification could reduce interactions with seabirds and other protected marine fauna. Each trial was conducted to compare catch composition between control and treatment net pairs. The 114 paired trials testing net illumination were conducted in Sechura Bay, Peru between January 2011 to July 2013. Results indicate statistically significant declines in the bycatch rates of guanay cormorants (Phalacrocorax bougainvilli), green turtles (Chelonia mydas) and Pacific seahorses (Hippocampus ingens) when LED lights were used. Additionally, results indicate that capture rates of target species, specifically guitarfish (Rhinobatos planiceps), were similar between illuminated and control nets. The 109 paired trials of sub-surface nets were conducted in Salaverry, Peru from March to December 2013. Results indicate statistically significant declines in the target catch of sharks and rays as well as declines in the catch of small cetaceans and sea turtles for modified nets set at greater depth than controls. Additional testing of both these technologies in Peru is planned or underway. Recommendations 1. Light illuminations trials in other fisheries, using other wavelengths of light and in other bycatch or target catch scenarios. 2. Assessment of light wavelengths that may be particularly effective for reducing seabird interactions. 3. Identify the next steps toward possible implementation or increased used of net illumination and a multi-taxa bycatch mitigation measure (i.e. cost of lights, means for importation or local manufacture, path to wider-scale implementation). 4. Phase 2 modification and testing of sub-surface net to further assess reductions in target catch and bycatch.