Growth differences between the Atlantic salmon parr,Salmo salar, of nursery brooks and natal rivers in the River Teno watercourse in northern Finland

Abstract

A comparison was done between growth in Atlantic salmon,Salmo salar, parr from natal rivers and small tributaries in the subarctic River Teno watercourse in northern Finland (70° N, 28° E). Salmon do not spawn in these tributaries but juveniles enter the brooks from their spawning rivers. Parr from these brooks (age groups 1 + and 2 +) were larger, so were their recorded annual growth increments, than those caught simultaneously in the River Teno. First year growth was also better in brook parr, although both groups had spent their first year in the main river. The brook water temperature was lower than that in the main rivers through-out the growing season. On the other hand, drifting food resources were more abundant in brooks. It has been suggested that better growth and a longer residence in fresh water result in the larger smolts being produced in the brooks relative to the main river. Differences in habitat selection and subsequent differences in the smolt age and size of fish from the same place of origin reflect the distinct life histories of the salmon in the River Teno.