Effect of gillnet mesh size on catch efficiency and bycatch in the Greenlandic lumpfish (Cyclopterus lumpus) fishery

The Greenlandic lumpfish (Cyclopterus lumpus) fishery is among the largest lumpfish fisheries in the world and serves as an important source of income for many local small-scale fishers. The fishery primarily targets females for their highly valued roe, using gillnets deployed from smaller vessels. However, challenges with unwanted bycatches raise concerns about the sustainability of the fishery. This study examines the impact of three different gillnet mesh sizes on the catch efficiency of lumpfish and non-target species. Results demonstrate that reducing the mesh size from the currently regulated 135 mm–120 mm (half mesh) can increase the catch probability of female lumpfish by 32 % while the capture for male lumpfish was estimated to increase by 240 %. Conversely, increasing the mesh size to 150 mm (half mesh) reduces female lumpfish catches by 70 % and 94 % for males respectively. The species composition was not affected to the same extent by changing mesh size. Despite the increased catch efficiency of lumpfish with smaller mesh sizes, the potential for higher seabird bycatch remains a significant concern, preventing recommendations for regulatory changes based on the current data.