Évaluation du capelan des divisions 2J+3KL en 2022 et l'évaluation des points de référence limites proposés

Abstract

The ocean climate on the Newfoundland and Labrador (NL) shelf fluctuates at decadal time scales, with potential impacts on ecosystem productivity. The warmer and potentially more productive period emerging since 2018 has continued in 2022. Overall conditions of the past three years are indicative of improved productivity at lower trophic levels in the NL bioregion (Northwest Atlantic Fisheries Organization [NAFO] Divisions [Divs.] 2J3KL). This includes earlier phytoplankton blooms, higher chlorophyll concentrations, and increased zooplankton biomass with a higher abundance of larger, more energy-rich Calanus copepods. Fish communities in NL marine ecosystems continue to experience overall low productivity, with total biomass well below pre-collapse levels. While the fish community has returned to a finfish-dominated structure, groundfish rebuilding stalled in the mid-2010s. Ecosystem indicators in recent years appeared to show improvements, but the lack of surveys in 2022 prevented an update of these trends. The 2J3KL Capelin stock has been depleted since 1991. The Capelin acoustic biomass index in 2022 was 262 kt (90% confidence interval 177–448 kt), a level generally higher than the post-collapse period (1991–2022), but well below the 1985–90 period. Capelin indicators derived from predator diets also suggest similar biomass levels in 2019 and 2022. There was no commercial Capelin fishery in 2022 due to market reasons. In 2022, peak timing of beach spawning was typical of the post-collapse period. The larval index was the highest observed in nearly a decade, but average compared to the post-collapse time series and low relative to the productive pre-collapse period. These two indices suggest 2022 was a weak year-class. Fall Capelin condition has been high since 2019; however, while there is confidence that condition was high in 2022, the estimate may not be directly comparable with prior estimates due to an earlier than usual sampling time in 2022. Since the Capelin forecast model is sensitive to fall condition, the results can only be described qualitatively due to uncertainty in the 2022 condition value. The Capelin acoustic biomass index in 2023 is expected to be at or above the level of 2022. A Limit Reference Point (LRP) was chosen for 2J3KL Capelin from a suite of LRP options based on the history of the stock trajectory and biology, and its importance to the ecosystem as a whole. Using Northern cod as an ecosystem indicator, a 640 kt Capelin acoustic biomass index was selected as the current LRP below which the Capelin stock and ecosystem are likely at risk of serious harm. This level is expected to support the growth of the Northern cod stock to levels last observed in the 1980s. Since 1991, with the exception of 2013 and 2014, the Capelin stock has been in the Critical Zone. The upper confidence limit (95th percentile) from the 2022 acoustic survey biomass index was 449 kt, indicating a very low (less than 5%) probability of being above the LRP. Consistent with the DFO decision-making framework, incorporating the precautionary approach requires that removals from all sources must be kept at the lowest possible level until the stock clears the Critical Zone.