Ensuring sustainable coastal fisheries under changing climate conditions and the scramble for fish resources

Grete Elisabeth Dinesen^1*Stefan Neuenfeldt¹Casper Willestofte Berg¹Asbjorn Christensen¹Josefine Egekvist¹Ole Ritzau Eigaard¹Jeppe Olsen¹Marie Storr-Paulsen¹Kirsten Birch Håkansson¹Thomas Højrup²Søren Qvist Eliasen³Kirsten Monrad Hansen²Josianne G Støttrup¹

• ¹National Institute of Aquatic Resources, Technical University of Denmark, Lyngby, Denmark
• ²Center for Sustainable Life Forms, Fjerritslev, Denmark
• ³Aalborg Universitet, Aalborg, Denmark

In the recent decade, local fishers in the Jammer Bay, western Skagerrak, experienced declining landings of cod (Gadus morhua) and plaice (Pleuronectes platessa) and were unable to fish up their quotas making it difficult to earn a livelihood. To enable an Ecosystem Based approach to Management (EBM), we applied the Systems Approach Framework (SAF). The fishers' concerns and perceptions of the system were brought forward and integrated into the analysis. We examined whether the declined coastal landings were due to over-fishing, changes in adult cod and plaice distribution, climate change or discards. To address these issues, we integrated data from different, sources including international landings data for Skagerrak, fisheries survey data for the Greater North Sea, Danish landings data and hydrographic models of thermal seabed habitats for the Jammer Bay area, and Danish landings and discards data from the Skagerrak. Our results showed declines in landings of cod and plaice in the Skagerrak appeared unrelated to quotas and effort. The fisheries survey data showed a regional shift in adult cod and plaice distribution from the southern and central North Sea areas to the northern North Sea areas. However, in the Jammer Bay area changes in where adult cod were caught were related to the distribution of suitable thermal habitats. No effects of changes in thermal seabed habitat were evident for adult plaice. The fisheries survey data showed that juveniles of both species occurred in high densities in the Jammer Bay area as compared to the remaining Skagerrak area and adjacent seas. Their occurrence coincided with the areas that were intensively fished, and high discards of juvenile cod and plaice were registered in the area during the period of the study. These results pointed to the need to implement protection measures for the juveniles of both species. The implementation of an Other Effective area-based Conservation Measure (OECM) would allow spatio-temporal closures to protect the juveniles while maintaining sustainable fisheries. In this study, we demonstrate how multi-sourced empirical data can be mobilized to provide knowledge-based advice for OECM implementation.