Effluents from fish farms

All fish farming facilities have effluent permits as regards nutrients and organic material from the environmental authorities that in practise limit the number of fish they can keep in the cages. Samples from the seabed are taken regularly below and near the farms in order to monitor the environmental conditions. Reports show that effluents of nutrients and organic materials from aquaculture are a minor environmental problem in Norway.

The long coastline with good water quality and extensive use of sites with currents ensuring good water quality are contributing factors. Most fish farming operations are located in deep fjords or along parts of the coast with high carrying capacity and good recipient water conditions.

The water along the Norwegian coast is generally of good quality. The natural concentration in the coastal flow accounts for about 95 percent of the total amount of phosphorus and nitrogen in coastal areas. Aquaculture is the dominant single source of the remaining 5 percent. Discharges of nutrients and organic matter from fish farms can have negative effects locally and possibly regionally. Regular environmental monitoring below and around fish farms is therefore a requirement. 

The Norwegian Directorate of Fisheries produces and publishes these environmental surveys.  

Opinions among scientists have been divided as to whether fish farming is causing over-fertilisation (eutrophication) in coastal areas. For this reason, the Norwegian Ministry of Fisheries and Coastal Affairs in cooperation with the Ministry of the Environment established an expert group in 2011. The group was given the task of assessing the degree of eutrophication in coastal areas, with a particular focus on areas with high fish farming activity such as the Bokna Fjord and the Hardanger Fjord. The expert group concluded that concentrations of nutrients in both fjords were within what could be called good to very good levels (based on criteria from the Norwegian Climate and Pollution Agency) in the water masses that were evaluated.