Atlantic salmon (Salmo salar) in the lower Nastapoka River, Quebec: distribution and origins of salmon in eastern Hudson Bay

Abstract

Atlantic salmon have been occasionally reported along eastern Hudson Bay, north of Richmond Gulf; however, in the Nastapoka River estuary they dominated gill-net catches over a 3-year period. The results of surveys of native fishermen suggest that this is the only anadromous stock in eastern Hudson Bay. Salmon are also present in the Nastapoka River above a 35-m coastal escarpment. It is proposed that they colonized the river from Ungava Bay by headwater exchange with the Koksoak River following deglaciation. Atlantic salmon and brook trout accounted for >80% of gill-net catches in the lower Nastapoka River and estuary. Salmon and trout were similar in size up to age 7. Trout growth was linear whereas salmon growth slowed, resulting in a smaller maximum size, but longevity was greater in salmon than in trout. Salmon matured at a greater age and had lower fecundity and reproductive potential than trout. In the estuary, both species consumed mainly littoral marine amphipods and marine fishes. The salmon population is located at the northern limit of the thermal optimum reported for the species. Habitat in the lower Nastapoka River may favour salmon over trout because of the rapid current in the restricted freshwater zone below the coastal waterfall. This habitat is threatened by the proposed diversion of headwaters for hydroelectric development.