Swedish experiences of the impact of aquaculture on the environment

The growing industry of aquaculture will have a great impact on the ecosystem of some lakes and coastal areas. In many parts of the world the impact is recognized and attempts are made to solve the problem. The effect of aquaculture on the environment is a function of (1) applied technique, (2) site location, (3) size of the production and (4) capacity of the receiving body of water. The discharges from aquaculture operations consist mainly of faecal pellets and feed wastes. which increase the load of organic matter and nutrients in the receiving body of water. The imposed regulations of aquaculture in Sweden are mainly based on the discharges of phosphorus, which is generally the limiting nutrient in lakes. In coastal sea areas, however, nitrogen is normally the limiting nutrient. The discharges from cultivation in open waters are not easily controlled compared to land based operations. This paper will mainly discuss environmental impact of fish farming in net cages and mussel cultivation and means to minimize the effects.