Sea/Brown trout (Salmo trutta)

 

While the same species, sea trout migrate to sea after two to three years to feed while brown trout remain in freshwater. Trout can be distinguished from salmon by their smaller pectoral fins, red tipped adipose fin, less forked tail and spot markings below the lateral line.  Trout in general have very flexible life histories varying from ferox trout in deep lochs and brown trout in freshwaters to sea trout that only go to sea for one or two years then remain in freshwater and those that return to the sea.

 

It is not clear exactly what makes a brown trout decide to go to sea although it is thought to be related to local environmental conditions and possibly genetics. Due to better feeding opportunities at sea, sea trout tend to be much larger than brown trout and as such many sea trout are female as their bigger size enhances egg production.

 

sea brown trout

Adult sea trout

Similar to salmon, trout smolts become silvery prior to their seaward migration as they undergo physiological changes to allow them to cope with life in saltwater. Unlike salmon, sea trout tend to remain within the coastal areas and do not undertake the massive migrations of their illustrious cousins. Some return to freshwater after a few months (finnock) whilst others remain at sea for up to several years before spawning. Trout can spawn on numerous occasions unlike salmon.

 

In recent years sea trout stocks have declined and efforts are needed to ensure that the populations continue to increase. Trout have a wide range of life histories, utilising many different types of habitat. More research is needed regarding habitat use and ecology, particularly in the marine phase of the lifecycle, to effectively manage and conserve trout stocks in west Sutherland.

 

Recent projects examining trout genetics have shown that there are distinct breeding populations occurring both within and between rivers. Trout from Sutherland waters are quite different genetically from rivers outside the area including the Ewe and the Tain. There are also differences in the genetics of trout found in the Laxford and Polla systems.

juveniletrout

  Juvenile trout

 

 

 

 

 

 

 

See also under publications:

 

  • Genetic assessment of sea trout populations in west Sutherland
  • Planktonic sea lice in Loch Laxford

 

 

 

 
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