Demersal pair trawl cod-end selectivity models

  • Published source details Galbraith R.D., Fryer R.J. & Maitland K.M.S. (1994) Demersal pair trawl cod-end selectivity models. Fisheries Research, 20, 13-27.


This study is summarised as evidence for the following.

Action Category

Decrease the circumference or diameter of the codend of a trawl net

Action Link
Marine Fish Conservation
  1. Decrease the circumference or diameter of the codend of a trawl net

    A replicated, controlled study in 1991 of an area of seabed in the North Sea off Scotland, UK (Galbraith et al. 1994) found that bottom trawl nets of smaller codend diameter improved the size selectivity of haddock Melanogrammus aeglefinus, whiting Merlangius merlangus and cod Gadus morhua compared to standard and wider diameters. Across three codend mesh sizes, the length at which fish had a 50% of escape increased with decreasing codend diameter for haddock (small: 30–40 cm, standard: 25–35 cm, wide: 20–30 cm), whiting (small: 36–46 cm, standard: 29–40 cm, wide: 23–33 cm) and cod (small: 35–43 cm, standard: 29–37 cm, wide: 23–32 cm). Data were collected in August 1991 from 40 trawl deployments using nine test codends by two commercial Scottish demersal pair trawlers. Combinations of three nominal codend diameters (2.2 m, 3.2 m and 4.2 m) and three nominal codend mesh sizes (90 mm, 100 mm and 110 mm) were tested with at least four hauls/combination. Codend covers of smaller mesh size retained escaping fish catch.

    (Summarised by: Chris Barrett)

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