Trawl Selectivity in the Barents Sea Demersal Fishery

Abstract

This chapter provides a general overview of the Barents Sea demersal trawl fishery. First, it reviews historical catch levels and current biomass status of four commercially important demersal species (cod, haddock, Greenland halibut, and redfish) and includes an overview of their management plan that has been carried out by the Joint Norwegian-Russian commission. Then, it presents the evolution of the technical regulations for improving size selectivity in this fishery and describes current challenges in gear selectivity. Later, this chapter describes the concept of size selectivity, introduces the selective parameters that define a selection curve, and progressively introduces different parametric models that describe the selection process. The most common experimental methods and gear used to collect selectivity data are described, and their advantages and disadvantages are discussed. Finally, this chapter describes an alternative, or a complementary method, to the conventional estimation of trawl selectivity-the FISHSELECT method. This method is based on morphology measurements and fish penetration models to estimate the selective properties of different mesh shapes and sizes at different mesh openings, which are later used to provide simulation-based prediction of size selectivity. FISHSELECT has already been applied to four important species of the Barents Sea Demersal Fishery, and the results have in all cases showed to be coherent with the results obtained from sea trial results.

Size selectivity and length-dependent escape behaviour of haddock in a sorting device combining a grid and a square mesh panel

“…We applied the covered-gear method (Wileman et al, 1996;Grimaldo et al, 2016) and used two covers to collect all fish escaping through the grid (grid cover) and the square mesh panel (panel cover) (Fig. 2).…”

Flow Field Pattern and Hydrodynamic Characteristics of a Grid Device Made with Various Grid Bar Spacings at Different Inclination Angles

“…Substantial strides have been achieved in refining the selectivity of trawl nets by modulating the design parameters of both the codend and BRD structures [3]. Grimaldo et al [9,10] conducted a flume tank test to juxtapose the hydrodynamic attributes of various grid materials. Their investigation revealed that, at towing speeds ranging between 1.25 and 1.5 m/s, the flow intensity of water amid a rigid grid registered 1.0-1.25 m/s, accompanied by a characteristic area coefficient spanning 0.64-0.65.…”