The effect of sweep bottom contact on the catch efficiency of haddock (Melanogrammus aeglefinus)

This paper illustrates the importance of length, angle and bottom contact of the sweep that connects the trawl and the otterboard for haddock (Melanogrammus aeglefinus) in Barents Sea. We compared the fishing efficiency of two different trawl setups over two cruises. During cruise 1, the sweep angle was 22.3° and the difference in sweep length with actual bottom contact was 30 m. During cruise 2, the average sweep angle was 12.0°, and the difference in length with actual bottom contact was 45 m. Setup 1 had less sweep bottom contact for both cruises. We estimated the relative change in length dependent catch efficiency of haddock between the two setups for each of the two cruises using catch comparison and catch ratio analyses. The results showed the importance of the length of sweep that actually contacted with the seabed for catching haddock. The differences between the two setups were significant for a limited range of length classes in both cruises, indicating that effect of the sweep bottom contact for this species is length dependent. The results also demonstrate that lack of control over the position of the doors in the water column when fishing semi-pelagic may cause loss of contact of the sweep with the seabed, reducing fishing efficiency for haddock.