This report contributes to the understanding of how the the socio-economic contribution of Nordic fisheries/aquaculture are affected by the environment and environmental management, with focus on nitrogen. The report contains two case studies of how the socio-economic contribution of Danish/Swedish cod fishery in the Western Baltic Sea are affected by the nitrogen in the sea, and on how salmon growth rates in aquaculture in the Bokna Fiord are affected by nitrogen concentration. A Nordic workshop was held with the title: Fisheries, aquaculture and the marine environment: Environmental challenges and regulation, with focus on nitrogen. The finding of the case studies was presented at the workshop, together with presentations made by invited speakers on the role of nutrients and their management for Nordic fisheries/aquaculture. The discussion at the workshop is summarized in this report.