Seasonal and ontogenetic patterns in the migration of anadromous brook charr (Salvelinus fontinalis)

Abstract

Migration patterns of brook charr (Salvelinus fontinalis) from the Sainte-Marguerite River, Québec, Canada, were investigated to explore the hypothesis that migratory behaviour changes according to size during the critical period of first downstream migration, when survival is likely to be related to size, and during subsequent seasonal movements. We hypothesized that as fish grow, they should adopt more conservative behaviours to protect the reproductive assets that they have accumulated. First downstream migration occurred over a month in spring. Larger juvenile charr migrated early, whereas smaller charr seemed to delay offshore migration. As predicted, migratory patterns of charr changed through ontogeny. Sea age 0 juveniles stayed in estuarine areas until October and overwintered outside their natal river. Sea age 1 juveniles returned to their natal river earlier in the fall and some of them overwintered there. Adults (some sea age 1 migrants and older migrants) undertook their upstream migration to spawning areas from July to September, larger ones migrating earlier than smaller ones. Postspawners migrated downstream after reproduction or overwintered in the river. Environmental differences related to geographical location may be responsible for the variation of migration patterns and other life-history traits observed among brook charr populations, emphasizing the co-evolution of anadromy and life history.