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Conference abstract2004

Long-term responses of a stream-dwelling grayling (Thymallus thymallus) population to catch-and-release regulations

Näslund Ingemar, Eriksson Torleif, Hannersjö David, Nordwall Fredrik


We used snorkel surveys and catch data to assess long-term effects of a catch and release fishery imposed 1989 on a population of stream-dwelling European grayling (Thymallus thymallus L.) in northern Sweden. From 1991 and onwards, catch (fish size ≥30 cm) increased from less than 2 fish per day to more than 5 per day in year 2001. A peak in angler catch of more than 7 fish per day was reached in 1999. A parallel increase in the grayling population size was indicated in snorkel count survey data from 1996-2000. The number of trophy-sized grayling (>50 cm) in the catch data increased dramatically between 1994 and 1997 and was still increasing in 2001. However, according to the snorkel surveys, recruitment declined from 1998 and onwards, resulting in a decrease in the total catch in 2000 and 2001. According to seasonal snorkel surveys and tagging data, the grayling population showed residency in summer but extensive movements between seasons. The reproductive potential of the Grayling population was estimated over the period of study and the effects of restricted regulations for reconciling fisheries with sport fisheries was analysed. We argue that it might take up to 10 years or even longer until the full effects of catch and release regulations could be observed and that such populations of grayling must be managed in a water system perspective incorporating also winter habitat

Published in

Publisher: Fourth World Fisheries Congress


Fourth World Fisheries Congress

      SLU Authors

    • Nordwall, Fredrik

      • Department of Aquaculture, Swedish University of Agricultural Sciences
      • Hannersjö, David

        • Department of Aquaculture, Swedish University of Agricultural Sciences
        • Eriksson, Torleif

          • Department of Aquaculture, Swedish University of Agricultural Sciences

        UKÄ Subject classification

        Fish and Aquacultural Science
        Environmental Sciences related to Agriculture and Land-use

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