Mise à jour de l'information sur les populations de saumon atlantique (Salmo salar) du sud-ouest du Nouveau-Brunswick (partie extérieure de la zone de pêche du saumon 23) pertinente pour l'élaboration d'un 2e rapport de situation du COSEPAC

Abstract

The purpose of this research document is to provide an update of Fisheries and Oceans Canada (DFO) information for the Outer Bay of Fundy (OBoF) Atlantic Salmon (Salmo salar) population [Designatable Unit (DU) 16] to support the development of a second status report of Atlantic Salmon in eastern Canada by the Committee on the Status of Endangered Wildlife in Canada. Information pertaining to OBoF Atlantic Salmon populations in southwest New Brunswick, corresponding to the outer part of Salmon Fishing Area 23, is compiled in this review, including population status, trends, life history characteristics, habitat and threats. Evaluation of the status of Atlantic Salmon in the OBoF is based on adult abundance monitoring for a number of index populations. For the Saint John River (SJR) upriver of Mactaquac Dam, the Nashwaak River (a tributary to the SJR downriver of Mactaquac Dam), and the Magaguadavic River, adult salmon counts and estimates of returns to enumeration facilities (e.g., fishway, counting fence) and subsequent spawners are assessed using a comparison of the estimated egg deposition (calculated from the estimated abundance and biological characteristics of Atlantic Salmon stocks) relative to a reference point known as the conservation egg requirement. Overall, the recent available data for OBoF Atlantic Salmon indicates that populations are persisting at low abundance levels and continuing to decline. Estimated adult abundance on the SJR upriver of Mactaquac Dam and on the Nashwaak River is presently 4% and 5% of their respective conservation requirements, and estimated egg deposition has declined at rates in excess of 75% over the last 3 generations (15 years) for both index populations. Adult returns to the Magaguadavic River were two MSW salmon in 2019, and have annually averaged less than two fish for the past decade. Small (one-sea-winter) and large (multi-sea-winter) salmon returning to rivers in the OBoF have both declined over the last 3 generations, approximately 81% and 79%, respectively. Moreover, these declines represent continuations of declines greater than 70% extending back over 25 years to 1993. Within the OBoF DU, threats of highest concern include the operation of hydro facilities in freshwater and unfavourable conditions in the marine environment linked with depressed population phenomena, along with aquaculture operations. To compensate for additive mortalities associated with hydroelectric dams and low marine survival, the salmon enhancement program at the Mactaquac Biodiversity Facility is currently being adaptively managed to produce captive spawning adults from wild-caught juvenile salmon and distribute to tributaries above Mactaquac Dam surplus offspring as unfed fry for supplementation purposes. However, freshwater threats, combined with low marine survival, still appear to be limiting recovery of the salmon populations in the SJR.