TOWARDS A REDUCTION OF POLLUTION FROM INTENSIVE AQUACULTURE WITH REFERENCE TO THE FARMING OF SALMONIDS IN NORWAY

The difficulties facing Norwegian fish farmers as a result of environmental issues are shared by other regions undergoing rapid development of intensive fish farming. It is estimated that the pollution from Norwegian fish farms associated with the production of about 150 000 t of salmonids in 1989 consisted of about 90 000 t of feed (dry weight), about 42 000 t of faeces (dry weight), 14 000 t of slaughter waste (wet weight), about the same quantity of dead fish and significant quantities of chemicals and antibiotics. Means to reduce this pollution are discussed and recommendations are made for the future. Feed presently provides the largest source of pollution. Adoption of improved feeding regimes and the use of new feed types could probably provide immediate benefits. Land-based farms, as opposed to net pens, may easily treat effluent water. Farms operating on recycled water represent the ultimate in reduction of pollution load. Future developments can be expected to improve the viability of such farms and allow the creation of a more environmentally-responsible direction for fish farming.