The freshwater fish farms have long been a notable source of pollution. The pollution derives from the waste feed as well as from the fish faeces. In addition, the fish farms take so much water from the watercourse that the reach between the water inlet and the downstream outlet can sometimes dry up, thereby impoverishing life in the watercourse. This applies to approx. 300 freshwater fish farms, the average length of the dead reach being 450 m.
There are no EC rules pertaining to aquaculture.
Freshwater fish farms:
These have been regulated21 since 1989 by means of a feed quota, i.e. the maximum permissible feed utilization during the course of a year. The feed quota is decisive for how great production at the fish farm can be; the fish cannot grow more than they are fed, and in practice not all the feed is converted to production. However, as the fish also take up a certain amount of water, it is possible for production to equal feed utilization. For the branch as a whole, the feed conversion quotient in 1993 was 1.01, i.e. 101 tonnes feed was utilized to produce 100 tonnes fish. The Counties have set feed quotas for all 500 freshwater fish farms, this being based on equations in which discharge in the watercourse is decisive for how great a fish farm production it can bear. The total feed quota is 35,000 tonnes.
The Danish rules also require that fish farms have a sedimentation basin such that the sludge settles in it rather than being led out into the watercourse. There are also rules on discharge levels for certain specified substances, on internal control of the inlet and outlet, and on operating records.
The problems with the freshwater fish farms are, firstly, their impact on downstream water quality, secondly, the resultant phosphorus loading of downstream lakes, and thirdly, the dead reach between the inlet and outlet.
The first problem, and to some extent the second, should have been solved by means of the feed quota system. A decrease in pollution from freshwater fish farms can in fact be measured in tonnes BOD5, nitrogen and phosphorus, although there is still a large number of fish farms - approx. 50% - that have an unacceptable impact on the environment downstream22. In this connection it can be important that many freshwater fish farms do not comply with the stipulated feed quotients. The question of "dead" reaches is more difficult to solve because until the year 2005 the fish farm owners have a kind of right of ownership over the water they divert into the farm. In 1995 a law was passed that gave the county authorities the right to ensure that sufficient water flows past the fish farm to keep the stream open, although they have to pay compensation for the water that is thereby diverted from the fish farm.
Saltwater fish farms:
These require individual authorization. Regulation is based on general requirements as to the maximum permissible feed conversion ratio and the maximum nitrogen content of the feed, as well as on individual requirements as to the maximum permissible N and P loading of the sea and maximum permitted feed utilization. In addition, effluent treatment is usually required, this being relatively easy to establish at such farms. The immunity from further environmental requirements given under the Environmental Protection Act has been reduced from 8 years to 4 years.
Marine fish farms:
These also require individual authorization, regulation being based on the same requirements as for terrestrial saltwater fish farms, except that treatment cannot be undertaken. The feed that is not used by the fish in the cages is washed away and deposits on the sea floor. The decisive factors are therefore feed utilization, location of the farm and the vulnerability of the marine area in relation to pollution.
Progress on the regulation of aquaculture can be summarized as follows: The freshwater fish farms remain one of the headaches of Danish environmental policy. The authorities have never succeeded in getting the sector to respect the law. In recent years the pressure on fish farms has to some extent limited pollution, but much remains to be achieved before an environmentally satisfactory result is attained. However, legal rulings are starting to be made in the many civil and criminal proceedings pending between the authorities and fish farm owners, and these show that in the long term the authorities will win the confrontation.
In contrast, limited expansion should be possible in the terrestrial
salt water and marine fish farm sectors25. However, because of overproduction in the whole
aquaculture sector, including in the Norwegian marine fish farms, new farms are not being
established at present.