Illuminating square meshed panels with white-coloured LED ropes to stimulate escape of undersized fish in beam trawl fisheries

Abstract

The Belgian beam trawl mixed-species fishery is associated with high bycatch and discard rates. Research on the effects of Square Mesh Panels (SMPs) and artificial light to improve the size selectivity of demersal trawls are relevant for ecosystem health as well as compliance with minimum conservation reference size (MCRS) requirements. This study was conducted as comparative fishing trials during five fishing campaigns in different areas. The influence of artificial illumination on the escape rates of undersized species was tested by placing white-coloured LED ropes on either a square mesh discard release panel (DRP) in the back of the net or a square mesh benthic release panel (BRP) in the belly of the net with a mesh size of 180 mm. Results showed that commonly discarded undersized European plaice (Pleuronectes platessa), escaped significantly more frequently through illuminated SMPs than through reference SMPs. The highest reduction was achieved in the clear waters of the Belgian part of the North Sea (BPNS) during daytime, where only 34 % of undersized plaice were found in the illuminated gear and 66 % in the reference gear. Cover codend catches showed that plaice mainly escaped through the BRP either when the BRP or the DRP were illuminated with LED ropes. Although the effect of a LED-DRP and a LED-BRP were evaluated on different fishing trials, the results suggest a greater reduction of undersized plaice when using a LED-BRP. In this study, no significant differences in catches of the other species were observed when SMPs were illuminated. This research shows that the use of LED rope as a Bycatch Reduction Light (BRL) offers opportunities to reduce bycatch of plaice in beam trawling, a mixed-species fishery where the options for reducing bycatch are otherwise very limited.