Effects of changes in the size and shape of codend on catch of Aegean Sea fishes

Published source details Stergiou K.I. (1999) Effects of changes in the size and shape of codend on catch of Aegean Sea fishes. ICES Journal of Marine Science, 56, 96-102.
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This study is summarised as evidence for the following.

	Action	Category
	Use a square mesh instead of a diamond mesh codend in a trawl net Action Link

Use a square mesh instead of a diamond mesh codend in a trawl net

A replicated, randomized, controlled study in 1993–1994 in two seabed areas in the Aegean Sea, Greece (Stergiou 1999, same experimental set-up as Petrakis & Stergiou 1997, and Stergiou et al. 1997) found that found that a bottom trawl net with a square mesh codend retained more fish overall than a diamond mesh codend of the same mesh size but this varied with species shape and size, and both retained fewer fish compared to a diamond mesh codend of smaller mesh size. The average proportion of retained versus escaped catch (for 36 fish species and 1 invertebrate) was higher for the square mesh than diamond mesh of the same size, but lower than smaller diamond mesh (square: 0.63, diamond: 0.49, small diamond: 0.93 retained). In addition, there were differences in the retained proportions of individual fish species between the square and diamond mesh codends of the same mesh depending on fish shape (round- or flatfish) and size (small or large). Experimental trawl deployments were conducted in the Trikeri Channel in October 1993 (5 hauls) and the North Euboikos Gulf in March 1994 (seven hauls). A trawl net was randomly assigned either a 20 mm square mesh codend or a 14 or 20 mm diamond mesh codend, and towed for 45–60 min at depths between 73–210 m. Small mesh (10 mm) covers over the codend sampled the escaping fish catch. All individuals caught in the covers and codends were identified and counted.

(Summarised by: Chris Barrett)