From semi-controlled environment to field trials: Testing pot entrance designs for Atlantic cod (Gadus morhua)

Gillnet fishing is associated with challenges, including bycatch of endangered, threatened, and protected (ETP) species and conflicts with marine mammals. Fish pots represent a sustainable alternative to gillnets due to their low bycatch risk of ETP species; furthermore, they can be designed to minimize seal predation. However, improvements in catch efficiency are necessary to enable their commercial implementation. Among the key factors influencing pot catch efficiency, the design of the pot entrance plays a crucial role. Therefore, optimizing the entrance is essential to improve catches. This study evaluated the catch efficiency of different experimental pot entrance designs under commercial fishing conditions (e.g., commercial fishing vessel and fishing grounds), building on findings from previous experiments in semi-controlled environments. We investigated the effects of entrance design parameters, including funnel netting colour, funnel length, and acrylic fingers as fish retention device on the catch rates of Atlantic cod (Gadus morhua). The colour of the funnel netting (transparent vs. white) had no significant effect on catch efficiency. In contrast, increased funnel length and the addition of acrylic fingers at the entrance significantly improved catch rates. Catch performance was also compared with a pot design used by a commercial fisher, which yielded higher catch rates than all experimental variants, indicating that design features beyond entrance configuration contribute to overall efficiency. These findings demonstrate the value of integrating semi-controlled experiments with field trials and the need for further design optimizations to support the development of more effective and sustainable fishing gear.