Divergent trends in life-history traits between Atlantic salmon Salmo salar of wild and hatchery origin in the Baltic Sea

• Main Authors: Vainikka, A., Kallio-Nyberg, I., Heino, M., Koljonen, M.-L.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Wiley-Blackwell 2010
• Subjects: Tornionjoki; Atlantic salmon; Salmo salar
• Online Access: http://pure.iiasa.ac.at/id/eprint/9223/

Four Atlantic salmon Salmo salar stocks in the Baltic Sea, varying in their breeding history, were studied for changes in life-history traits over the years 1972-1995. Total length (L_{T}) at age of captured (L_{TC}) fish had increased throughout the study period, partly due to increased temperature and increased L_{T} at release, (L_{TR}) but also due to remaining cohort effects that could represent unaccounted environmental or genetic change. Simultaneously, maturation probabilities controlled for water temperature, L_{TC} and L_{TR} had increased in all stocks. The least change was observed in the River Tornionjoki S. salar that was subject only to supportive stockings originating from wild parents. These results suggest a long-term divergence between semi-natural and broodstock-based S. salar stocks. Increased L_{T} at age explained advanced maturation only marginally, and it remains an open question to what extent the generally increased probabilities to mature at early age reflected underlying genetic changes.