Nitrogen non-point pollution from agriculture is the dominating source of eutrophication of Danish fjords. Long-line mussel production is an alternative measure to costly agricultural measures to achieve good ecological status of fjords. This paper investigates farmers’ economic incentives to buy nitrogen quotas from compensatory mussel producers. The Danish fjord Limfjorden is used as case study area, and an agricultural model is developed including crop-distribution, soil quality , leaching and retention among the farms in case-catchments. The main conclusion is that trading nitrogen-quotas between mussel farms and agriculture provides a potential for cost-effective mitigation of eutrophication in this type of fjords.