Cod-end selectivities of a modified bottom trawl for three fish species in the Aegean Sea

Published source details Tokaç A., Lök A., Tosunoğlu Z., Metin C. & Ferro R.S.T. (1998) Cod-end selectivities of a modified bottom trawl for three fish species in the Aegean Sea. Fisheries Research, 39, 17-31.
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This study is summarised as evidence for the following.

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	Use a larger mesh size Action Link

Use a larger mesh size

A replicated, controlled study in 1995–1996 in coastal waters of the Aegean Sea, Turkey (Tokac et al. 1998) found that increasing the codend mesh size of a bottom trawl improved the size-selectivity of three fish species, for both diamond and square mesh. The length at which fish had a 50% chance of escape was greater for the largest mesh sizes (across both square and diamond mesh) compared to the smallest: for red mullet Mullus barbatus (44 mm: 12–13 cm, 40 mm: 11–12 cm, 36 mm: 10–11 cm), annular seabream Diplodus annularis (48 mm: 11–12 cm, 44 mm: 8–9 cm, 40 mm: 8 cm, 36 mm: 6–7 cm) and axillary seabream Pagellus acarne (44 mm: 12–13 cm, 40 mm: 11 cm, 36 mm: 9–10 cm). The effect at the intermediate mesh sizes varied however between species and codend types (see paper for data). Data were collected from 85 trawl deployments by a research vessel from October 1995 for 12 months. Eight different codends of diamond and square mesh with four different mesh sizes were tested: 48 mm, 44 mm, 40 mm and 36 mm. Deployments were 1 h at 30–110 m depth. A small mesh (24 mm) cover attached to the codend collected catch escaping through the meshes. Fish caught in both the codends and cover were sorted by species, counted and lengths recorded.

(Summarised by: Chris Barrett)