Spatiotemporal mapping of the Norwegian wrasse fishery suggests impacts on catch rates for multiple target species

Abstract Understanding the distribution and intensity of fishing activity is fundamental to assessing anthropogenic impacts on target species and surrounding ecosystems. Here, we present a method to integrate digital vessel tracking data from automatic identification system and vessel monitoring system with sales slips to map inter-annual fishing pressure in a small-scale fishery (SSF; vessels <12 m) across multiple spatial resolutions. We found that the Norwegian wrasse fishery (a passive gear fishery) experienced proportional declines in both fished area and reported catch (22% each between 2021 and 2023) over the study period, and that spatial restrictions on fishing activity reduced the regional catch. Fishing activity was highest between Bergen and Stavanger, and focused mainly within coastal archipelagos, rather than fjord regions. We grouped fishing pressure at three spatial scales (regional, 5 and 1 km2) and calculated annual catch per unit effort (CPUE) per polygon, then analysed the relationships between CPUE between consecutive years for each species. This revealed a quadratic relationship for the three main target species, corkwing (Symphodus melops), goldsinny (Ctenolabrus rupestris), and ballan wrasse (Labrus bergylta), where CPUE was lower than expected in polygons which had experienced high CPUE in the preceding year. The reduction in CPUE indicated that intensive wrasse fishing reduces densities of target species, and the mapping method presented in this study can facilitate for improved targeted studies of fishing impacts on these ecologically important species. We discuss the limitations of integrating multi-source spatial datasets in SSF monitoring and offer recommendations for future spatially explicit models of fishing pressure.