Relative size selectivity of a four-panel codend with short lastridge ropes compared to a flexigrid with a regular codend in the Barents Sea gadoid trawl fishery
We examined relative selectivity of a four-panel codend with short lastridge ropes to facilitate open meshes, to a flexigrid and a conventional two-panel codend.
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A logistic, additive mixed-model regression was used to analyse relative retention probabilities of three gadoid species.
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Compared to the conventional flexigrid-codend combination, the four-panel codend retained negligible undersized fish.
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The results show that with a simple solution, catches of undersized fish can be reduced to meet objectives of fisheries managers.
Abstract
Size-selective grids in the Barents Sea trawl fisheries have demonstrated large variation in sorting capacity. When combined with dynamic catch-control systems for regulating catch quantity, surplus fish are washed out at the surface. The objective of this study was to develop a codend concept that releases more undersized fish than the most commonly used size–selectivity device in the Barents Sea trawl fishery (flexigrid combined with a two-panel 130 mm codend). Fishing with twin trawls, a four-panel 153 mm codend concept with short lastridge ropes to force open meshes was compared with a flexigrid combined with a 130 mm mesh codend, in terms of size selectivity for cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and saithe (Pollachius virens). Compared to the grid–codend setup, the four–panel codend with short lastridge ropes retained about half of 54.5–59.4 cm gadoids, with catches of undersized cod, haddock and saithe reduced by 90 (ci = 85–94), 92 (ci = 88–96) and 86 % (ci = 79–92) respectively. The study demonstrated that the four-panel codend concept releases more undersized fish than the flexigrid-codend combination.
