A comparison of size selection of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) by bottom longlines and otter trawls

Published source details Halliday R.G. (2002) A comparison of size selection of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) by bottom longlines and otter trawls. Fisheries Research, 57, 63-73.
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This study is summarised as evidence for the following.

	Action	Category
	Use hook and line fishing instead of other commercial fishing methods Action Link

Use hook and line fishing instead of other commercial fishing methods

A replicated, paired, controlled study in 1991 in two pelagic areas on the central Scotian Shelf in the North Atlantic Ocean off Nova Scotia, Canada (Halliday 2002) found that longlines had a higher or similar size-selectivity for cod Gadus morhua and haddock Melanogrammus aeglefinus at larger hook sizes only, compared to using trawls. The length at which line-caught cod had a 50% chance of escape (selection length) was 41 cm, 54 cm and 63 cm for three hook sizes, from smallest to largest respectively. The two largest hook sizes were higher than a diamond mesh codend (50 cm), but only the largest hook size was higher than a square mesh codend (56 cm). For haddock, average lengths caught on the two smaller hooks (49–50 cm) were intermediate between those of the diamond and square mesh nets (46–51 cm) and that for the largest hook size was highest (53 cm). Fishing took place in October 1991 using a commercial fishing vessel in depths of 73–123 m. A total of 14,700 circle hooks of three sizes (9.7 mm, 11 mm and 14.7 mm barb length) were deployed on 53 longline sets fished for 6 h. Two otter trawl nets were used: a 130 mm diamond mesh codend and a 130 mm square mesh codend. A small-mesh (40 mm diamond) codend was used to sample the length ranges of fish. Three to seven trawl tows were made each day over 13 days, towed parallel to the set longline gear. The length of captured fish was recorded.

(Summarised by: Chris Barrett/Natasha Taylor)