Testing a size sorting grid in the brown shrimp (Crangon Crangon Linnaeus, 1758) beam trawl fishery

The North Sea brown shrimp (Crangon crangon Linnaeus, 1758) fishery became Marine Stewardship Council (MSC) certified in 2017. As part of the certification, the fishermen proposed to incrementally increase the mesh size of the codend used from 22 mm to 26 mm. As this increase in mesh size could result in a substantial loss of marketable sized brown shrimp (shrimp with total length equal or higher than 50 mm), a combination of a size sorting grid with a bar spacing of 6 mm and a 22 mm codend was proposed by the Danish fishermen as a possible alternative to the increase in codend mesh size.

The objective of the proposed gear was to release shrimp smaller than the marketable size before they reach the codend, while potentially limiting the loss of marketable sized shrimp. Therefore, the aim of this study was to investigate the size selective performance of brown shrimp in the above-mentioned gears.

The results showed that the grid reduced catches of shrimp under the marketable size of 50 mm. Moreover, the combination of the grid and a 22 mm diamond mesh codend, with an estimated L50 of 44.9 mm and a selection range of 15.6 mm, had an overall selective performance similar to that of a 26 mm diamond mesh codend, both for shrimps under and above the marketable size.