Size selection of silver hake (Merluccius bilinearis) by otter trawls with square and diamond mesh codends of 55–60 mm mesh size

Published source details Halliday R.G. & Cooper C.G. (2000) Size selection of silver hake (Merluccius bilinearis) by otter trawls with square and diamond mesh codends of 55–60 mm mesh size. Fisheries Research, 49, 77-84.
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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, paired, controlled study in 1994–1995 in two offshore areas of seabed in the North Atlantic Ocean, Canada (Halliday & Cooper 2000) found that square mesh codends improved the size-selectivity of a trawl net for silver hake Merluccius bilinearis, compared to diamond mesh codends. The estimated length at which 50% of hake were predicted to escape was higher in square mesh codends than diamond, and between square meshes was higher in the larger mesh size (square, 60 mm mesh: 26 cm, 55 mm mesh: 23 cm; diamond, 60 mm mesh: 16–19 cm). Data were collected on two chartered commercial inshore otter trawlers during five experimental surveys in the Emerald and LaHave basins (central Scotian Shelf) between July 1994 and March 1995. During each survey, one experimental codend (one survey each of 55 or 60 mm square mesh, and three surveys of 60 mm diamond mesh with or without a 89 mm chafer section – see paper for gear specifications) was towed on one boat parallel to a small mesh control codend (19 mm) on the other, for a total of 98 valid paired hauls in 180–265 m depth. In all experiments, a size-sorting escape grid was installed in front of the codend. Silver hake catches were subsampled for weight, and fish length (snout to the middle of the tail fin) recorded.

(Summarised by: Natasha Taylor)