Meeting Abstract
Brown trout (Salmo trutta) show remarkable phenotypic variation in life-history traits, including migration tendency. Some populations are dominated by resident (non-migrating) and others by migrating individuals. Both environment and genetic background influence the life-history strategies, but the strength of the genetic component is poorly understood. Here, we studied how rearing conditions and genetic background affect the smolting process and smolt migration activity. We reared one supposedly migratory, one supposedly resident population of brown trout and their F1-hybrids in common-garden conditions. The fish were tagged with PIT-tags and the experiments were performed when the fish were 2–3 y.o. Fish were divided equally in semi-natural streams with ambient temperature lake water. Half of the tested fish were introduced to the stream from hatchery conditions during the winter, while the other half of the fish fed on natural food sources in the streams starting from the previous autumn. Fish movement and its direction were monitored using four PIT antennas in each stream. On the second year of smolting, 53 fish were euthanized during peak migration and gill samples collected for measuring Na,K-ATPase activity and the number of Na,K-ATPase pumps –indicators of smolting process in anadromous salmonids. Both were higher in fish from the migratory than the resident population, and intermediate in hybrids, suggesting smolting physiology has a strong genetic component even after a long isolation in freshwater. We found similar results on downstream swimming activity. Overall, the study gives a more insight to how life-history decisions are regulated by the environment and the genetic background.
