MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14433

ABSTRACT: In the Baltic Sea, brown trout have been shown to make extensive use of the marine environment; however, little is known regarding movement between the freshwater and marine environments or the interaction between life histories within a population. First, we analyzed otolith structure and chemistry of hatchery origin (n=26) anadromous brown trout with known life history and maternal origin to evaluate the efficacy of otolith microchemistry to distinguish between freshwater habitat in northern Sweden and marine rearing in the northern Baltic Sea. We then described the maternal origin and migration patterns of wild anadromous brown trout (n=59) originating from the Ume and Vindel River catchment in Northern Sweden. Otolith microchemistry revealed the majority (73%) of fish made 3 or more (up to 5) migrations to the marine environment prior to capture, presumably to feed. We observed a high degree of life history diversity, where trout first migrated to sea from age-1 to age-4 and either migrated back to freshwater once each year (presumably to spawn) or spent more than a year in the marine environment before returning to freshwater. While 42% of the wild anadromous trout were judged to be the progeny of a resident mother, sex ratio, age and inter-habitat migrations were similar for resident and anadromous progeny highlighting the role of resident life histories in producing anadromous adults. Results reported here provide managers with new information to support the protection and enhancement of brown trout populations in places where they have declined.