Alternative Strategy for Size Selectivity of Trawls

Recent research in fish biology has demonstrated that older individuals of several fish species including cod, can have better reproductive efficiency than younger mature fishes – and are therefore important for the relevant stocks. These findings are not supported by the current strategy used to improve trawl selectivity, which aims at releasing small sized individuals and retaining larger ones, resulting in selection curves where the retention likelihood increases with fish size. However, when combining existing technologies for selection devices, it would be possible to develop gears with adopted size specific retention likelihood which also take into account the reproductive importance of large fish. Here, we present the results from a recent sea trial, carried out in Baltic Sea, demonstrating that it is possible to achieve a so-called ‘bell-shaped’ selectivity curves by means of technological modifications in the standard trawl, used in the Baltic cod-directed fishery.