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Report, 2006

Salmonids in northern Swedish rivers

Östergren, Johan


This introductory essay summarizes the life history of anadromous brown trout (Salmo trutta L.), (ie. sea trout), and Atlantic salmon (Salmo salar L.) and the status in the present day for the local river stocks in the Baltic Sea. Historically there existed at least 90 locally adapted stocks of salmon in the Baltic Sea and today only 25 of them can utilize natural rivers for reproduction due to anthropogenic impact. The number of sea trout stocks is unknown but the general status in present day is worse than for salmon. This paper discusses the history and the effects of habitat degradation on local river stocks of Atlantic salmon and sea trout. The results of anthropogenic impact are lack of suitable spawning and nursing habitat, over exploitation through fishing and negative effects of river regulations for water power production. Historical log driving and constructions of floatways did most certainly contribute to a decline in salmon and trout production. In many rivers and streams in the Baltic area the natural stocks have gone extinct due to dams used for water regulations. Hatching and releasing of reared salmon and sea trout has been one strategy for the authorities to compensate for loss of aquatic habitat and to deal with declining catches in the fisheries. The genetic effects of these conservations strategies are further discussed in the paper. Recently, many habitat restoration programs have been carried out, but rarely has an evaluation of effects of restorations been done. Some evaluation methods are presented and discussed in this paper. To preserve the natural stocks of salmon and sea trout there is a need for further research on the biology of the two species. There is a lack of knowledge on the sea phase and migration biology of sea trout post smolts, although it’s known that the majority of the sea trout is caught as immature fish as by catch in the whitefish fishery, which is devastating for the natural production. There is very limited knowledge in both species on post spawning behaviour and survival, and what effect the survival rate has on a population scale. The genetic structure in sea trout and long term effects of releasing reared sea trout and salmon is unknown. These are very important subjects that need to be considered in the development of a future management and conservation strategy

Published in

Rapport / Sveriges lantbruksuniversitet, Vattenbruksinstitutionen
2006, number: 49
Publisher: Vattenbruksinstitutionen, SLU

    SLU Authors

    • Östergren, Johan

      • Department of Aquaculture, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Fish and Aquacultural Science

    Permanent link to this page (URI)