The main environmental problems associated with fish farming in Denmark are attributable to the dam, the “dead reach” and nutrient and organic matter discharge. The environmental regulation of fish farming in Denmark started with the Environmental Protection Act of 1974, the Statutory Order of 1985 forbidding wet feed, and the Action Plan on the Aquatic Environment of 1987. In the case of freshwater fish farms, the latter was implemented through the measures stipulated in the 1989 Statutory Order on Fish Farms.

The impact of Danish legislative measures to reduce and regulate the environmental effects of freshwater fish farms can be summarized as follows:

- the number of fish farms has been reduced from about 800 in 1974 to about 500 at present;

- production has tripled since 1974 and has been stable since 1989;

- a change from wet to dry feed has reduced the environmental impact of the farms;

- the national goals of the Action Plan on the Aquatic Environment of 1987 for reducing fish farm discharges of organic matter, nitrogen and phosphorus have been fulfilled.

The main remaining problems are that:

- the local impact of fish farms on downstream stream quality is still much too high in about 15% of cases;

- the problem of the passage of migrating invertebrates and fish is still unsolved at some farms;

- the problems posed by “dead reaches” are still unsolved.

It is concluded that sustainable fish farming is possible in Denmark, but with the present technology production will have to be significantly reduced.