Selectivity and escapement behaviour of five commercial fishery species in standard square- and diamond-mesh codends

• Published in: ICES Journal of Marine Science
• Main Authors: Frandsen, Rikke P., Madsen, Niels, Krag, Ludvig A.
• Format: Text
• Language: English
• Published: Oxford University Press 2010
• Subjects: Articles; Gadus morhua
• Online Access: http://icesjms.oxfordjournals.org/cgi/content/short/67/8/1721; https://doi.org/10.1093/icesjms/fsq050

<qd> Frandsen, R. P., Madsen, N., and Krag, L. A. 2010. Selectivity and escapement behaviour of five commercial fishery species in standard square- and diamond-mesh codends. – ICES Journal of Marine Science, 67: 1721–1731. </qd>The Danish fishery for Nephrops ( Nephrops norvegicus ) is often conducted in a mixed-species setting, characterized by high rates of discards of several target species, including Nephrops and cod ( Gadus morhua ). Experiments were conducted to investigate and compare the selective properties of a standard 70 mm square-mesh codend (standard SMC) and a standard 90 mm diamond-mesh codend (standard DMC). Selectivity estimates for five commercial species are provided for both codends. The standard SMC yielded higher estimates of length at 50% retention/mesh size (hereafter SF) for Nephrops and roundfish than did the standard DMC, but no effect of codend type on SF was found for plaice ( Pleuronectes platessa ). Moreover, a novel codend cover design allowed assessment of the preferred direction of escapement in the codend. Whiting ( Merlangius merlangus ) and Nephrops showed pronounced, but opposite, vertical preference in the direction of escapement, with whiting escaping upwards and Nephrops downwards. A significant ( p < 0.05) difference in the direction of escapement between the two codends was found for haddock ( Melanogrammus aeglefinus ) and whiting. Owing to the relatively small catches, the outcome is probably most applicable to Nephrops- directed fisheries under similar conditions, and caution should be taken not to extrapolate the results to other fisheries.