Trial of a new escape panel concept to reduce cod catches in a mixed demersal fishery

Abstract

The species selectivity of demersal fishing gear in mixed whitefish fisheries needs to be improved for vessels with limited cod (Gadus morhua) quota which are encountering increasing abundances of cod in some areas of the North Sea, particularly around Shetland. Based on the known behavioural characteristics of cod within a demersal trawl, a new escape panel concept was designed and tested using an alternate haul methodology aboard a 12 m trawler. A modified (henceforth “experimental”) net was made by incorporating an upwardly inclined panel connected to a horizontal middle panel that extends back over and beyond a large mesh escape panel in the lower side of the net extension. The results of 22 paired comparative hauls are presented which demonstrated the relative selectivity of the experimental net by reference to a control net. Catch rate data showed a significant reduction in cod in the experimental net by an estimated 81% (p < 0.001). Importantly, no significant differences in the catches of other main target species were recorded between the two nets. The results indicated that the escape probability of cod increased for larger fish, whereas no significant length effects were found for haddock (Melanogrammus aeglefinus) or plaice (Pleuronectes platessa). Further research and development is recommended to evaluate the escape panel concept in commercial conditions and to optimise this promising method for vessels in the mixed demersal fishery.