Floated cod pots with one entrance reduce probability of escape and increase catch rates compared with pots with two entrances

Abstract

The development of low impact and fuel efficient (LIFE) fishing is being paid growing attention. Pot fishing has lower environmental impact and fuel consumption than most other fishing methods. However, pots typically have low capture efficiency for most ground-fish species, and efforts to develop effective commercial pots are needed. Bycatch of red king crab (Paralithodes camtschaticus) is a severe problem in the coastal fishery for cod (Gadus morhua) in the Barents Sea. In a previous publication, we demonstrated that cod pots floated off the bottom eliminated this problem. Our original bottom-set cod pot has two entrances in order to increase the rate of entry of fish, but when this pot is floated, fish that search for food by following chemical cues up-current will only encounter the entrance that is oriented down-current. We therefore compared the catch rates of floated pots with one and two entrances, and predicted that the new design with only one entrance would achieve higher catch rates due to a lower rate of escape. Pots with one entrance caught significantly more cod and haddock (Melanogrammus aeglefinus) than pots with two entrances. The catch rate of cod above minimum landing size (≥44cm) of pots with one entrance was 82% higher than that of pots with two entrances. Pots that were snagged and did not float properly caught large numbers of king crab. The larger catches of pots with one entrance could be explained by lower escape rate from this design. The observed difference in catch rates between the two pot types indicates that more than 50% of the large cod and haddock that entered the pot with two entrances escaped. There is therefore great potential for increased catching efficiency of pots through improved pot design.