Assessing the causes of Atlantic salmon declines in eastern Canada and the efficacy of smolt-to-adult supplementation for the restoration of endangered populations

Healthy, sustainable Atlantic salmon (Salmo salar) stocks are important economically, ecologically, and culturally to Canada. However, many populations have been severely decreasing since the 1980s, leading to an endangered listing for many populations by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). This is particularly evident in Cape Breton, Nova Scotia, where many rivers are classified as endangered. Parks Canada has been monitoring the adult salmon population on Clyburn Brook in the Cape Breton Highlands National Park for over 30 years and has documented a steep decline by over 95% since 1991. In the research outlined here, we will collaborate with Parks Canada to examine historical data on the temporal pattern of this decline and whether it matches that in other rivers from the region. Additionally, a central aim of this proposal is to quantify the efficacy of smolt-to-adult supplementation in Clyburn Brook, where salmon have collapsed to near local extirpation. Recently, smolt-to-adult supplementation (SAS) has been used as an emergency recovery strategy, where wild juvenile salmon from the Clyburn are transported to Dalhousie University and grown into adults. The adults are then returned to the river for spawning. However, no formal assessment of the survival, freshwater movements, reproductive activity, and marine migration behaviour of these salmon has been conducted. Using acoustic telemetry, we will monitor these events in SAS salmon and compare them to those of wild individuals from the Clyburn and from other local rivers. This assessment will allow us to determine, for the first time, the efficacy of the SAS program, and provide important information as to whether SAS salmon are reproducing and thus contributing to future generations, and behaving and surviving as expected. These issues are of paramount importance to Parks Canada, as well as Mi'kmaq conservation groups, Fisheries and Oceans Canada, the Atlantic Salmon Federation and others stakeholders, especially since the Species at Risk Act stipulates that recovery strategies must be developed and employed. This assessment will also inform SAS programs planned for other endangered salmon rivers in Canada.