Can the lost migratory Salmo trutta stocks be compensated with resident trout stocks in coastal rivers?

Abstract

Abstract The migration patterns and recapture rates of migratory and resident trout stocks ( Salmo trutta ) were compared by tagging and releasing hatchery-reared smolts of both migratory types in the same coastal rivers, Merikarvianjoki (river A) and Viantienjoki (river B), flowing into the Gulf of Bothnia, the Baltic Sea. There is no longer native trout production in these open rivers. The resident trout stocks originated from closed streams. The resident Karvianjoki (R1_ A ) trout released in river A remained resident more often (70%) than the migratory Isojoki trout (M1_ A ) (16%) ( P B ) and migratory Iijoki trout (M2_ B ) and their crossed offspring, released in river B, did not differ; about 30% of the recaptures from each genetic group were caught in the river and the rest in the sea. A few fish from both migratory types had a long feeding migration into the main basin of the Baltic Sea. The growth rate to catch size did not differ between the resident and migratory trout (R1_ A /M1_ A or R2_ B /M2_ B ). The migratory M1 trout had somewhat better survival and gave a higher catch than the resident R1 trout ( P P