Incidental bycatch is a well-known challenge in gillnet fisheries throughout the world, and the fishery for North Atlantic lumpfish Cyclopterus lumpus roe is no exception. In Greenland, the fishery was Marine Stewardship Council-certified in 2015 but has pending conditions related to bycatch quantification, enforcement and mitigation strategies. To improve this situation and to assess the potential impact of bycatch, we collected independent on-board observer data on non-target fish and seabirds over 2 seasons (2019 and 2021). We recorded 6 fish species, but the only species constituting >1% of the lumpfish landings was the spotted wolffish Anarhichas minor. The bycatch of fish likely had little impact on the involved fish stocks. We recorded 4 seabird species, of which common eider Somateria mollissima was most common. When extrapolated to the entire West Greenland lumpfish fishery, the estimated bycatch of common eider was considerably higher in 2019 (19938; 95% CI: 3486-59661) than in 2021 (9802: 1260-29940) due to a longer fishing season in 2019. On average, for 2019 and 2021, the bycatch was modelled to reduce the growth potential for the West Greenland winter population by 51%. In comparison, the current hunting level (16538 birds yr-1) reduced the growth potential by 30%. The larger impact of bycatch was mainly due to a larger proportion of adults and females being targeted. The common eider bycatch impacts mainly the breeding population in Canada and Southwest Greenland and less so in Northwest Greenland. As mitigation, we recommend temporal closures of the fishery unless modified gillnets, which markedly reduce bycatch, become available.

Bycatch in gillnets is a global issue and mitigation measures that balance target species catch rates, bycatch reduction and fisher support are scarce. In the North Atlantic lumpfish fisheries, bycatch includes marine mammals and seabirds, and there are no permanent technical initiatives to reduce the bycatch. In the West Greenland fishery, common eider bycatch is several thousand individuals annually. We explored if bycatch in this fishery could be reduced by modifying standard lumpfish gillnets by adding a 45 cm high small-meshed net panel to the bottom part of the net. We tested the nets in combination with standard nets and estimated catch rates in a controlled setting in 2021 and in the commercial fishery in 2022. The modified nets had a 71% reduced bycatch rate for common eider and a 25% reduced catch rate for female lumpfish. A combination of the panel and increased seaweed entanglement was the most likely explanation for the effect. In addition to the effect of the net modification, the common eider bycatch decreased significantly during the season, and we recommend studying the net effect further and exploring the option of postponing the fishing season as a simpler way of reducing bycatch.

No abstract

Diamond-mesh codends are the most commonly used in demersal trawls. However, mesh geometry tends to vary in these codends during fishing, which leads to a less well-defined size selection process. This leaves one questioning the rationality of regulating exploitation patterns based on mesh size when size selection and/or variation between hauls is highly variable. While it has been speculated and theoretically investigated how much the variability in mesh geometry may contribute to the variability in size selection, it remained to be quantified experimentally. Therefore, we compared the size selectivity of a simple diamond-mesh codend, where meshes are subjected to variation in geometry, with a rigid diamond-mesh codend, where the geometry of the meshes were kept constant. For Atlantic cod (Gadus morhua) the simple diamond-mesh codend was found to have 45% more variation in size selection than the codend with constant mesh geometry. This confirms theoretical predictions and may guide research towards codend designs with more well-defined size selection properties.

No abstract