Otolith microchemistry and acoustic telemetry reveal anadromy in non-native rainbow trout (Oncorhynchus mykiss) in Prince Edward Island, Canada

This study examined the migratory patterns of introduced rainbow trout (Oncorhynchus mykiss) in three rivers in Prince Edward Island, Canada, using acoustic telemetry and otolith microchemistry. Only 6% of acoustically tagged fish in three river systems left coastal embayments. A cohort of rainbow trout in all three rivers entered saline waters. Habitat use differed among migrants in the three rivers, as Montague River fish occupied estuary habitat (mean 20.79 PSU) more often than West River and Dunk River fish that tended to occupy both riverine tidal (mean 1.27 and 4.29 PSU, respectively) and freshwater habitats (<0.5 PSU), particularly during summer months (July and August). A second cohort of rainbow trout remained exclusively in fresh water. Migratory individuals were more likely to arise from anadromous mothers, but freshwater mothers produced migratory offspring in all sites. Migratory individuals were significantly larger than nonmigratory freshwater residents. This study suggests that partial residency was the primary strategy, with prominent tidal occupation, while secondary marine and freshwater contingents were included in the full range of successful migratory strategies.