Effects in Catch Efficiency As Consequence of Lifting the Sweeps in the Northeast Arctic Gadoid Bottom Trawl Fishery

Fuel consumption and environmental concerns have led bottom trawlers fishing cod (Gadus morhua) and haddock (Melanogrammus aeglefinnus) in the Barents Sea to use semi-pelagic doors. However there are concerns on whether this change affects fish herding and consequently the catch efficiency of the gear. During two cruises we investigated the effect on catch efficiency between two different setups where different lengths of sweeps were kept at the seabed. Further, these setups enabled us to estimate the herding efficiency of the sweeps on the seabed.

We estimated that the setup with the lifted sweeps captured in average 33% less cod than the setup that kept the sweeps at the seabed. This loss could be explained by that the sweeps at the seabed were able to herd 45% of the cod into the catch zone of the gear. For haddock we found a length dependent loss in catches when lifting the sweeps from the seabed.

The study shows that introducing supposedly advantageous changes as lifting the trawl doors from the seabed can lead to substantial catch loses. Considering then the increase in effort needed to maintain the same catches, the fishery could become less efficient and less environmentally friendly.