Individual repeatability in marine migratory behaviour: A multi-population assessment of anadromous brown trout tracked through consecutive feeding migrations

Abstract

Despite that the study of individual repeatability is a common topic in behavioral ecology, virtually nothing is known about inter-annual variability in the marine migratory behavior of iteroparous salmonids that can complete multiple feeding migrations in their lifespan. Behavioral data from 38 anadromous brown trout (Salmo trutta), tracked by acoustic telemetry in 2–3 consecutive marine feeding migrations in two Norwegian fjord systems, were analyzed for intra-individual repeatability in key aspects of their marine migration. Individual brown trout displayed significant inter-annual consistency in marine area use and in the timing of marine exit (i.e. when they returned to spawning rivers), but not in the timing of marine entry or the time spent in the marine environment each year. Our study raises new questions about how anadromous brown trout respond to changing conditions and anthropogenic factors in the marine environment. Intra-individual repeatability of brown trout linked to changing environmental conditions should therefore be a focus for future studies.