The brackish waters of the Bras d’Or Lake in Cape Breton, Nova Scotia, are a UNESCO World Biosphere Reserve and unique in-land sea connecting to the Atlantic Ocean through three narrow estuarine channels. The area was once known for its robust Atlantic salmon populations, but salmon have experienced troubling declines in recent years. Through partnerships with Eskasoni First Nation, Fisheries and Oceans Canada (DFO), and local angling groups and conservation societies, the Ocean Tracking Network’s (OTN) monitoring infrastructure monitors salmon migrations among inland rivers, the Bras d’Or Lake and the Atlantic Ocean.

For juvenile salmon, the Bras d’Or Lake is an important rearing habitat. Approximately half of all tagged smolts in this study remained in the lake over winter rather than migrating to feeding grounds off Greenland. This decision to stay in the lake was linked to a more robust body condition; thus, direct migration to sea may reflect immediate nutritional needs. For adult salmon, the movements of 60 individuals tagged after spawning in a natal river draining to the lake showed that those in good physical condition tended to spend the winter in the river and migrated to the lake and Atlantic Ocean in spring. In contrast, energy-depleted fish moved to the sea in autumn after spawning.

The survival of salmon was highest when they overwintered in the rivers and low when they left the river quickly after spawning. Once in the ocean, adult salmon migrated to Greenland through the Gulf of St. Lawrence’s Strait of Belle Isle. Results from both studies show marked seasonal and spatial variation in the way that salmon use the Bras d’Or Lake, which has implications for their survival and management.

Dalhousie scientists continue this research and have expanded salmon tracking studies to include investigations of migration, survival, and spin-off effects of hatchery-reared salmon released in Bras d’Or Lake as adults alongside wild populations.