Evaluation of the quality of whitefish (Coregonus lavaretus) in Lake Sølensjøen in the municipality Rendalen, SE Norway

Sammendrag

This project was initiated by Sølensjøen Lotteierforening (Lake Sølensjøen fisher’s association). The project aimed at evaluating the status of the whitefish stock after 3 years of intensified harvest have been carried out in an effort to increase individual whitefish growth and enhance the contribution of Arctic char in the catches. Since 1990, annual yield of whitefish have varied between 4.8 and 18.6 tons in Lake Sølensjøen (5.5 kg/ha in average). During the past three years, the annual yield has been between 15 and 16 tons. The findings in this project indicate that the increased harvest has not yet resulted in any clear changes in the Arctic char and whitefish populations. The typical catch size of whitefish in the lake is 35 cm and 450 g. The individual growth of whitefish however seemingly starts to be stunted already at three years of age. The majority of females where sexually mature at age 4 years. This implies that the whitefish population still experiences growth limiting factors. A limited material on Arctic char shows distinct growth stagnation before age 5 years, which is likely caused by resource competition with whitefish. In order to increase individual whitefish growth rates and the yield of Arctic char in the lake, we recommend maintained or even increased fishing effort. Further on we encourage the use of trap net systems that optimizes the quality of the fish harvested. Trap nets are also less size selective than gill nets, which will prevent fishery induced selection decreasing the whitefish individual size at maturation.