<abstract xmlns="http://www.w3.org/1999/xhtml"><p>The aim of the present study was to determine the mean size and age of migrating salmon, <italic>Salmo salar </italic>L., and sea trout, <italic>Salmo trutta </italic>L., smolts in three rivers of the Nemunas River drainage area from different climatic sub-regions in Lithuania. Research indicates there were significant differences of migrating fish age and size between stocked and natural smolt populations. In natural populations salmon and sea trout smolts aged 2+ dominated, but up to 82% of all migrating smolts of the stocked population in Siesartis River were aged 1+. The artificially-reared salmon and sea trout smolts in the Siesartis River were significantly larger than wild fish in the 1+ age group of migrants, and, accordingly, they reached smolt size and were ready to migrate earlier. The high density of salmonid parrs in the Siesartis River and intraspecific competition could have also prompted 1+ age group smolts to migrate. It is hypothesized that the phenomenon of early smolt migration in the Siesartis River could have been a local adaptation to the long migration route, or it could have resulted from density-dependent competition caused by imbalanced stocking programs.</p></abstract>

The aim of the present study was to determine the mean size and age of migrating salmon, Salmo salar L., and sea trout, Salmo trutta L., smolts in three rivers of the Nemunas River drainage area from different climatic sub-regions in Lithuania. Research indicates there were significant differences of migrating fish age and size between stocked and natural smolt populations. In natural populations salmon and sea trout smolts aged 2+ dominated, but up to 82% of all migrating smolts of the stocked population in Siesartis River were aged 1+. The artificially-reared salmon and sea trout smolts in the Siesartis River were significantly larger than wild fish in the 1+ age group of migrants, and, accordingly, they reached smolt size and were ready to migrate earlier. The high density of salmonid parrs in the Siesartis River and intraspecific competition could have also prompted 1+ age group smolts to migrate. It is hypothesized that the phenomenon of early smolt migration in the Siesartis River could have been a local adaptation to the long migration route, or it could have resulted from density-dependent competition caused by imbalanced stocking programs.

Age and size of migrating Atlantic salmon, Salmo salar L., and sea trout, Salmo trutta L., smolts in Lithuanian rivers

Institute of Ecology, Nature Research Centre, Akademijos 2, LT–08412 Vilnius–21, Lithuania

Coastal Research and Planning Institute Klaipėda University, Lithuania

Fisheries & Aquatic Life

The aim of the present study was to determine the mean size and age of migrating salmon, Salmo salar L., and sea trout, Salmo trutta L., smolts in three rivers...

Age and size of migrating Atlantic salmon, Salmo salar L., and sea trout, Salmo trutta L., smolts in Lithuanian rivers

Published Online: Jan 30, 2013

Page range: 257 - 266

DOI: https://doi.org/10.2478/v10086-012-0029-8

Keywords
wild population, smolt migration, age, stocking impact, stream salmonids

This content is open access.

Age and size of migrating Atlantic salmon, Salmo salar L., and sea trout, Salmo trutta L., smolts in Lithuanian rivers

Published Online: Jan 30, 2013

Page range: 257 - 266

DOI: https://doi.org/10.2478/v10086-012-0029-8

Keywordswild population, smolt migration, age, stocking impact, stream salmonids

This content is open access.

Keywords
wild population, smolt migration, age, stocking impact, stream salmonids