Évaluation du stock de Saumon Atlantique à Terre-Neuve-et-Labrador en 2023 (ZPS 1 à 14b)

Abstract

Twenty-four populations of Atlantic Salmon (Salmo salar) were monitored in 2023. Returning adult salmon were counted on 23 rivers using monitoring fences or fishways, and returns were estimated on one river using a combination of a fish counting fence and snorkel survey. Stock status was estimated for 19 monitored populations. In 2023, 16 rivers had sufficient time series data to compare adult returns to the previous generation. Of these 16, 12 showed declines in total returns with eight having declines over 30%. Twelve rivers had sufficient time series data to compare adult returns to the previous three generations. Of these 12, nine showed declines in total returns with seven having declines over 30%. This met the criteria to trigger a full stock assessment. Smolt abundance estimates were available for three of five Newfoundland rivers where monitoring occurs annually. Smolt abundance was below average on two of three rivers with estimates in 2023, and modelling suggests that smolt production has declined significantly over the past three generations on Rocky River (Salmon Fishing Area [SFA] 9), Conne River (SFA 11), and Western Arm Brook (SFA 14A). Marine survival is considered a major factor limiting the abundance of Atlantic Salmon in Newfoundland and Labrador (NL). Marine survival estimates for the 2023 adult return year were available for Rocky River (2.6%) in SFA 9 and Garnish River (1.1%) in SFA 11, both of which were at least 56% below average. Available data suggest that marine survival for Conne River salmon remains low (<2%). In 2023, estimated spawning escapements (eggs) on Labrador rivers were in the Critical Zone on Southwest Brook, Muddy Bay Brook, and Sand Hill River, and the Healthy Zone on English River. Of the 15 assessed rivers in Newfoundland, ten were in the Critical Zone, one was in the Cautious Zone, and four were in the Healthy Zone. Preliminary harvest estimates for the 2023 Labrador Indigenous and subsistence fisheries were inferred from logbooks and were 16% above the previous generation average and 17% above the three-generation average. Estimates of catch in the 2023 recreational Atlantic Salmon fishery were inferred from angler log returns and an angler phone survey. Estimates of angler effort, retained and released salmon were below the previous generation average in NL. Sea surface temperatures during the 2023 summer months were much warmer than normal on the NL shelf and Gulf of St. Lawrence. The last three years were the warmest in the NL region (2022 being the warmest). Average monthly July river temperature in Labrador was the highest on record (since 1994), with temperatures >25°C for 9.2% of July and 2.1% of August. In Newfoundland, temperatures were >25°C for 14% of July and 2.5% of August. Temperatures exceeding 25°C may have physiological and potentially lethal impacts on juvenile and adult Atlantic Salmon. Marine conditions over the past 3–5 years are indicative of improved productivity at the lower trophic levels across the NL bioregion. These include high nutrient inventories, earlier phytoplankton blooms, and above-normal abundance of both small and larger, more energy-rich Calanus spp. copepods. Marine ecosystem conditions indicated overall limited productivity of the fish community. Total biomass of the entire fish community remained below pre-collapse levels with minor recovery up to the early 2010s, followed by subsequent declines. In recent years (2019–23), ecosystem indicators have suggested that conditions could be improving from the lows in the mid-late 2010s.