Study

Evaluation of codends with sorting grids, exit windows, and diamond meshes: Size selection and fish behaviour

  • Published source details Grimaldo E., Sistiaga M. & Larsen R.B. (2008) Evaluation of codends with sorting grids, exit windows, and diamond meshes: Size selection and fish behaviour. Fisheries Research, 91, 271-280

Actions

This study is summarised as evidence for the following.

Action Category

Fit a size-sorting escape grid (rigid or flexible) to a fish trawl net

Action Link
Marine Fish Conservation

Fit mesh escape panels/windows to a trawl net

Action Link
Marine Fish Conservation
  1. Fit a size-sorting escape grid (rigid or flexible) to a fish trawl net

    A replicated, controlled study in 2005–2006 of two seabed areas in the Norwegian Sea, off Finmark and Troms, northern Norway (Grimaldo et al. 2008) found that fish trawl nets fitted with a rigid size-sorting escape grid did not improve the size-selection of cod Gadus morhua and haddock Melanogrammus aeglefinnus compared to trawl nets fitted with square mesh escape windows or a large diamond-mesh codend. In nets with a grid, the average length (56.1 cm) at which half of cod were estimated to be retained (selection length) was similar to nets with escape windows (53.9 cm) but lower than a large diamond mesh codend (60.7 cm). For haddock, average selection length was similar between all three codends: (grid: 50.2 cm, escape windows: 50.6 cm, large diamond: 49.9 cm). In addition, all retention lengths were higher than the minimum landing sizes of 47 cm (cod) and 44 cm (haddock). Data were collected from 62 deployments in December 2005–March 2006 of a trawl net with two codends: one an experimental codend and one a control diamond-mesh codend with a small-mesh inner net. Experimental nets were a 135 mm diamond-mesh codend fitted with a 55 mm sorting grid (Sort-V); a 135 mm diamond-mesh codend fitted with two side escape windows; and a codend of 155 mm diamond mesh.

  2. Fit mesh escape panels/windows to a trawl net

    A replicated, controlled study in 2005–2006 of two seabed areas in the Norwegian Sea, northern Norway (Grimaldo et al. 2008) found that fish trawl nets fitted with square mesh escape windows did not improve the size-selection of Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinnus, compared to trawl nets fitted with rigid size-sorting escape grids or a large diamond-mesh codend. For cod, the average length at which fish had a 50% chance of escape (selection length) was similar in nets with escape windows (53.9 cm) to nets with a grid (56.1 cm) and lower than a large diamond mesh codend (60.7 cm). For haddock, average selection length was similar between all three codends: (escape windows: 50.6 cm, grid: 50.2 cm, large diamond: 49.9 cm). In addition, all selection lengths were higher than the minimum landing sizes of 47 cm (cod) and 44 cm (haddock). Data were collected from 62 deployments, off Finmark and Troms in December 2005–March 2006, of a trawl net with two codends: one an experimental codend and one a control diamond-mesh codend with a small-mesh inner net. Experimental nets were a 135 mm diamond-mesh codend fitted with two lateral escape windows; a 135 mm diamond-mesh codend fitted with a 55 mm sorting grid (Sort-V); and a codend of 155 mm diamond mesh.

Output references

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