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Brown trout

Salmo trutta

Photo: Rickard Gustafsson/AzotePhoto: Anders Tedeholm/Azote

Brown trout is an ecologically and culturally important species in many freshwater habitats. It is a host of the threatened freshwater pearl mussle Margaritifera margaritifera.

Conservation genetic management advice 

  • Avoid stocking except for strict conservation purposes. If stocking is needed, individuals that are closely related to the naturally occurring local population should be used.
  • Protect and restore spawning grounds.
  • Manage water systems as metapopulations. That is, allow for genetic exchange among populations (connectivity), and make sure that larger areas covering several spawning grounds are managed jointly.
  • Ecological importance and good genetic knowledge make this species suitable for environmental monitoring of genetic diversity.

Threats to genetic biodiversity 

Mixed stock fisheries at sea show a high proportion of long distance migrants in the catch, indicating fishing of several populations. Such mixed stock fisheries risk the depletion of weak populations and will, as a consequence, reduce genetic biodiversity.

Loss of spawning grounds due to habitat modifications.

Large scale stocking will reduce genetic biodiversity, and might erase unique genetic elements needed for local adaptations.

Knowledge on genetics in the Baltic (2017)

Brown trout is one of the most well studied species within population genetics. The species has a strong genetic substructure with distinct populations; at least one population exists per river/creek.

Many populations have been genetically analyzed. This basic information on the genetic characteristics can be used in management, for instance to analyze which spawning populations that are being fished during mixed stock fishery. This is important in order to assure that weak populations are not overharvested. Genetic information can also be used to identify populations suitable for releases for conservation purposes.

There is a metapopulation structure (multiple populations connected via gene flow) in restricted areas of the Baltic Sea, e.g. around the islands Bornholm and Gotland. Genetic exchange between populations that spawn in separate small creeks around these islands appears important for maintaining the genetic diversity of the metapopulation as a whole.



Linda Laikre

Lovisa Wennerström

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