Improved bycatch reduction in the mixed demersal trawl fishery for Norway pout (Trisopterus esmarkii)

Abstract

In this study, we compared the bycatch reduction capacity of a trawl fitted with a standard rigid sorting grid with that of a trawl fitted with a newly developed, flexible system called the Excluder. We conducted the fishing trials in the Norway pout (Trisopterus esmarkii) small-meshed trawl fishery in the North Sea. Catch data were analysed by species and length using the catch comparison and catch ratio method. The Excluder significantly reduced the bycatch (in weight) relative to the standard grid for blue whiting (Micromesistius poutassou) (−35.6%), mackerel (Scomber scombrus) (−93.3%), horse mackerel (Trachurus trachurus) (−99.3%), herring (Clupea harengus) (−89.9%), haddock (Melanogrammus aeglefinus), (−98.6%), whiting (Merlangius merlangus) (−99.3%), cod (Gadus morhua) (−97.1%), European hake (Merluccius merluccius) (−98.0%), and greater argentine (Argentina sphyraena) (−24.5%). For Norway pout there was a marginal decrease in the overall catch efficiency of −1.4%. The observed bycatch reduction efficiency is explained by the larger sorting area of the Excluder relative to the grid's area and by the differences in behaviour between Norway pout and the bycatch species. While it contributes to reduce bycatch of quota regulated species, the Excluder also can potentially affect the profitability of the fishery.