Aquaculture - a problem for the environment ?

Abstract

Aquaculture is often considered as a source of pollution. The pollution associated with aquaculture has special features due to the fact that the fish-farming environment and the surrounding ecosystem are inextricably linked. There are a variety of forms of pollution connected with aquaculture : organic pollution, chemical pollution, bacteriological pollution, genetic pollution etc... The amount of pollutants may be high in the near vicinity of the fish farm and also relatively high, in proportion to the total pollution, further afield. It is estimated that the production of a metric ton of salmon involves a sea area of 1 sq km and that Norwegian fish farms contribute 8 % of nitrogenous and 14 % of phosphates discharged into the North Sea. The law is not adapted to such problems as those encountered in fish-farming. European regulations, inspired by Danish legislation, primarily seeking to control the composition of foodstuffs seem to be in preparation. The quickest way to reduce pollution produced by aquaculture seems for the moment to be by reducing the quantity of food used, by increasing it’s calorific value (thereby reducing the quantity of suspended solids) and by replacing a part of the proteins with lipids. The introduction of this type of food stuff however demands a high degree of technical know-how. The future of downstream water treatment seems to be limited by the difficulty of treating the low levels of pollutants and the large volumes involved. Environment sensitive aquaculture can serve as a model for studies on enviromental cost.