Study

Selectivity of a 120mm diamond cod-end and the effect of inserting a rigid grid or a square mesh panel

  • Published source details Graham N., O’Neill F.G., Fryer R.J., Galbraith R.D. & Myklebust A. (2004) Selectivity of a 120mm diamond cod-end and the effect of inserting a rigid grid or a square mesh panel. Fisheries Research, 67, 151-161

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, paired, controlled study in 2001 of two seabed areas in the North Sea off Norway (Graham et al. 2004) found that fish trawls fitted with a rigid size-sorting grid (Sort-V) improved the size-selection of one of three fish species compared to conventional standard trawl nets. The length at which fish have a 50% chance of escape was higher in codends with a grid compared to conventional codends for haddock Melanogrammus aeglefinus (with: 37.2 cm, without: 35.5 cm), but was not statistically different for saithe Pollachius virens (with: 49.1 cm, without: 46.4 cm) and Atlantic cod Gadus morhua (with: 45.6 cm, without: 40.9 cm). In addition, for haddock, but not saithe or cod, this value increased with increasing catch size in the grid codend but was similar for all catch sizes in the standard codend (data reported as statistical models). Fishing trials were carried out in October 2001 on The Patch and Alle Bank fishing grounds off Bergen. Seven hauls were done with each of two codends: a 120 mm diamond mesh codend fitted with a 35 mm rigid sorting grid and 40 mm guiding panel (Sort V system), and a standard 120 mm diamond mesh codend. Selection (i.e. sizes of fish of each species caught) of each codend was calculated by comparing catch to that caught in a small mesh (50 mm mesh) codend trawled simultaneously.

    (Summarised by: Leo Clarke)

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

    A replicated, paired, controlled study in 2001 in two areas of seabed in the North Sea off Norway (Graham et al. 2004) found that trawl nets fitted with a square mesh escape panel in the codend did not improve the size selectivity of undersized haddock Melanogrammus aeglefinus, saithe Pollachius virens or Atlantic cod Gadus morhua, compared to a conventional diamond mesh codend without a square mesh panel. The estimated length at which a fish has a 50% chance of escape was not statistically different between codend types for three of three species: haddock (with: 34.4 cm, without: 35.5 cm), saithe (with: 50.5 cm, without: 46.4 cm) and Atlantic cod (with: 44.5 cm, without: 40.9 cm). In addition, this value increased with increasing catch size in both codend types for haddock but was similar at all catch sizes for saithe and cod (data reported as statistical models). Fishing trials were carried out in October 2001 in The Patch and Alle Bank fishing grounds off Bergen. Seven deployments were done with each codend type: one trawl net a standard 120 mm diamond mesh codend fitted with a 3 m long square mesh panel (110 mm mesh) and one a 120 mm diamond mesh codend (see paper for specifications). Size-selection of each codend was calculated by comparing codend catches to catch in a small mesh (50 mm mesh) codend towed simultaneously.

    (Summarised by: Leo Clarke)

Output references

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