Marine fish farms
Marine fish farms have existed in Denmark since the 1970’s. Cultivation of fish in the ocean uses nets or long-line arrays that are moored to the sea floor. The Danish production of marine fish is primarily rainbow trout.
In order to avoid damages to the marine fish nets, they are taken to mainland during winter months. As such, the duration of the Danish marine fish production is usually only for 6-7 months. Juvenile trout (600-1000 g), bought from freshwater fish farms, are released into the enclosures and will in the following 6-7 months grow to about 2-4 kg.
Currently there are 18 marine fish farms in Denmark, and in 2010 they produced approximately 10 000 tonne fish.
Marine fish farming can have a variety of effects on the marine environment, though the degree of pollution depends on the size and location of the farm, as for instance the overall current can influence the spread of pollutants.
Production of marine fish can have an environmental impact locally and regionally through the discharge of nutrients such as nitrogen and phosphorus, solid waste, medicines and antifoulants. Waste feed and faeces from fish farms can collect on the seabed under the nets. An increase in organic matter can have an impact on the benthic environment, affecting the nature and chemistry of sediments, and can reduce the diversity of animals living there.
Farmed fish are susceptible to infestations of parasitic sea lice that cause considerable stress to fish. Sea lice on farmed fish could potentially be transferred to wild fish populations. The occurrences of lice have had huge repercussions on the wild salmon stocks in Norway. In addition, there can be potential problems with escapees.
Regulation and environmental protection
Marine fish farms located less than 1 nautical mile from the coast is regulated according to the Planning Act and the Environmental Protection Act.
Marine fish farms located more than 1 nautical mile from the coast is regulated according to the Water Plans, Environmental Target Act, the Statutory Order on Habitats, the Fisheries Act and the Water Action Plan.
The Danish Environmental Protection Agency is the prime enforcement authority of legislation regulating marine fish farms in Danish waters.
Environmental approvals of marine fish farms
Danish marine fish farms are obligated to apply for an environmental approval according to the Regulation on the establishment and operation of ocean farms by the Ministry of Food, Agriculture and Fisheries. The application is send to the Danish AgriFish Agency.