Test of 300 and 600 mm netting in the forward sections of a Scottish whitefish trawl

Comparative fishing trials investigated the effect of increasing the mesh size in the forward sections of a trawl from 120 and 160 mm to (i) 300 mm and (ii) 600 mm on the catches in the Shetland mixed whitefish fishery.The 300 and 600 mm trawls respectively caught an estimated 49 and 75% fewer Atlantic cod (Gadus morhua), 79 and 93% fewer megrim (Lepidorhombus whiffiagonis), 36 and 68% fewer ling (Molva molva), and 28 and 53% fewer hake (Merluccius merluccius) than the control trawl at all lengths. The 300 mm trawl caught ∼40% more haddock (Melanogrammus aeglefinus) than the 600 mm and control trawls which had similar catch rates. The catch rates for monkfish (Lophius piscatorius) were length dependent and the 300 mm trawl caught ∼50% fewer monkfish at 30 cm with no significant difference > 76 cm. The 600 mm trawl caught ∼90% fewer monkfish at 30 cm with no significant difference > 83 cm. Both the 300 mm and 600 mm trawls caught significantly fewer saithe (Pollachius virens) above 53 cm.