The influence of twine thickness on the size selectivity of polyamide codends in a Mediterranean bottom trawl

Published source details Sala A., Lucchetti A. & Buglioni G. (2007) The influence of twine thickness on the size selectivity of polyamide codends in a Mediterranean bottom trawl. Fisheries Research, 83, 192-203.
Share Tweet Email

This study is summarised as evidence for the following.

	Action	Category
	Use a different twine type in a trawl net Action Link

Use a different twine type in a trawl net

A replicated, controlled study in 2004 of one shallow inshore and one deeper offshore seabed area, in the central Adriatic Sea, off Italy (Sala et al. 2007) found that using a thinner diameter of twine in the codend of a trawl net improved the size-selectivity of five of five fish species. Across both areas, the length at which fish had a 50% chance of escaping was highest using thin twine compared to thick twine for whiting Merlangius merlangus (thin: 11 cm, thick: 8 cm), European hake Merluccius merluccius (thin: 9 cm, thick: 8 cm), red mullet Mullus barbatus (thin: 9 cm, thick: 7 cm), common pandora Pagellus erythrinus (thin: 9 cm, thick: 7 cm) and poor cod Trisopterus minutus capelanus (thin: 10 cm, thick: 7 cm). Data were collected by research vessel from trawl deployments on two different fishing grounds. In the offshore area (35 nm from the coast, 70 m depth), 34 trawl deployments were done between April 2004–May 2004. In the inshore area (5 nm off the coast near Ancona, 20 m depth), 20 deployments were made in September 2004. Two codends of different twine thicknesses were tested: 2.4 mm diameter (thin) and 2.9 mm diameter (thick – industry standard) and alternated daily on the same trawl net body. Small mesh covers attached over each codend sampled the fish escaping through the meshes.

(Summarised by: Chris Barrett)