Abstract
. Fish farming activities based on salmonid smolt production in cages were monitored in a coastal freshwater lake in western Norway. Yearly ongrowth in the fish farm increased from 350kg in 1979 to 15150kg in 1985, while maximum biomass of standing stock increased to nearly 14000kg in the same period. Maximum daily mortality observed was 0·37% of total stock in August 1983 due to an Ichthyobodo necator infection. Except for 1983, between 61 and 73% of annual amount of feed was used in the second half of the year. Total feed amount used in 1979–85 was 77750kg. The phosphorous effluents decreased from 88 to 90% of the feed content to 80·4% in 1984–85. A set of easily calculated parameters for judging management possibilities and success in cage farming is proposed: annual heat sum; mortality rate; growth rate; feed conversion; and phosphorous retention in fish.
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