Codend selection in American plaice: diamond versus square mesh

Published source details Walsh S.J., Millar R.B., Cooper C.G. & Hickey W.M. (1992) Codend selection in American plaice: diamond versus square mesh. Fisheries Research, 13, 235-254.
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This study is summarised as evidence for the following.

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	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 1988–1990 in two offshore bottom fishing grounds in the Northwest Atlantic Ocean, Canada (Walsh et al. 1992) reported that bottom trawl nets with square mesh codends did not improve size selection of long rough dab Hippoglossoides platessoides compared to conventional diamond mesh codends at three different mesh sizes. Data were not statistically tested. The length at which plaice had a 50% chance of escape was lower in square mesh codends at all three mesh sizes tested (130 mm: 31 cm, 140 mm: 31 cm, 155 cm: 32 cm) than diamond mesh (130 mm: 31 cm, 140 mm: 38 cm; 155 cm: 38 cm) and was reported to increase marginally with increasing mesh size. Catches from square and diamond mesh codends of three different mesh sizes were compared during three experimental trials on the Scotian Shelf (140 mm mesh, 31 hauls) and Grand Bank (155 mm mesh, 29 hauls) in October 1988 and on the Grand Bank in March 1990 (130 mm mesh, 32 hauls). All hauls were done using a standard bottom trawl net modified with twin codends: each test codend (square or diamond) on one side towed with a small mesh (39 mm) control codend on the other (sides rotated during each trial). Codend catches from each haul were sorted and plaice were counted, and their lengths measured.

(Summarised by: Rosslyn McIntyre)