An assesment of the compatibility between fish farming and the Norwegian coastal environment
Raa, J.; Liltved, H. (1992). An assesment of the compatibility between fish farming and the Norwegian coastal environment, in: De Pauw, N. et al. (Ed.) Aquaculture and the Environment: reviews of the International Conference Aquaculture Europe '91, Dublin, Ireland, June 10-12, 1991. EAS Special Publication, 16: pp. 51-59 In: De Pauw, N.; Joyce, J. (Ed.) (1992). Aquaculture and the Environment: Reviews of the International Conference Aquaculture Europe '91, Dublin, Ireland, June 10-12, 1991. Special Publication European Aquaculture Society, 16. European Aquaculture Society: Gent. ISBN 90-71625-10-9. 536 pp., more In: Special Publication European Aquaculture Society. European Aquaculture Society: Bredene. ISSN 0774-0689, more |
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| Abstract | Pollution from industry, sewage systems, and agriculture is a threat to commercial fish farming. The process of fish farming itself has environmental impacts. In sheltered bays sludge depositions under the cages have been observed. If the sediment also contains residual antibiotics, bacterial pathogens resistant to antibiotics may develop. The use of antibiotics can be reduced by prophylactic actions, proper management and operation. New and robust cage systems have made it possible to move farms from sheltered bays to more exposed localities. Combined with improved feed composition and feeding routines, the problem with sludge deposition has been reduced. In this paper the impact on Norwegian coastal waters of phosphorus, nitrogen and organic matter released from fish farms is discussed and compared with the loads from decomposition of roe and milt from wild stocks of fish, and nutrients from industrial, domestic and agricultural discharges. Feed for farmed fish has mainly a marine origin. Nutrient released from surplus feed and excretory products will drift northwards with the coastal current. Through the food chain the nutrient will be brought back into biomass along the coast of Norway and in the Barents Sea. Nutrients from land-based activities transported from the German Bight and the Baltic Sea seem to have an unpleasant impact on the concentration ratio of nitrogen to phosphorus in southern Norwegian coastal waters. A shift in this ratio may favour growth of some algae species and increase toxin production. Solving the disease problem without much use of antibiotics will be the main challenge of the fish farming industry in the future. |
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