Heavy Exploitation of a Dense Resident Population of Arctic Char in a Mountain Lake in Central Norway

Abstract

During a period of 6 years (1979-1984), heavy exploitation of a dense resident population of Arctic char (Salvelinus alpinus) was carried out with gill nets in Lake Øvre Stavåtjønn, a small mountain lake in central Norway. The estimated density in 1979 was 1,100 Arctic char (71 kg) per hectare. The total annual yield decreased consistently from 18.0 kg/hectare in 1979 to 3.0 kg/hectare in 1984. This high fishing mortality greatly influenced the population structure, turnover (production-to-biomass ratio), age composition, growth rate, and length-frequency distributions. The yield of Arctic char that weighed over 125 g was greatly increased from 1979 to 1984. According to the Graham model, the maximum sustainable annual yield should be 7 kg/hectare, a reasonable estimate of annual surplus production that could be harvested in the lake under constant exploitation.