Évaluation du stock de morue du Nord (divisions 2J3KL de l’OPANO) en 2021

Abstract

The Newfoundland and Labrador climate experiences important fluctuations at decadal time scales, with potential impacts on ecosystem productivity. These large scale changes are linked to phases of the North Atlantic Oscillation (NAO) and patterns in large-scale ocean circulation (e.g., increased Labrador Current transport). The coldest period on record (late 1980s to early-1990s) coincided with the Northern cod stock collapse and has been linked to significant changes in the ecosystem. Warmer than average conditions have been observed over the last three years. Primary (phytoplankton) and secondary (zooplankton) productivity have improved to near or above average levels since around 2015, but with changes in zooplankton seasonality (lower spring, higher summer and fall biomass signals) and community structure (higher dominance of small-sized copepods). Ecosystem conditions in the Newfoundland Shelf and Northern Grand Bank (NAFO Divs. 2J3KL) remain indicative of overall limited fish community productivity, with low abundance of key forage species and total Research Vessel (RV) trawl survey biomass remaining well below pre-collapse levels. Diet composition of cod and other key predators indicate food limitation. Increases in groundfish observed from the mid-2000s to mid-2010s were associated with bottom-up processes, but have stalled as key forage species like Capelin and Shrimp have declined. Cod productivity has been linked to Capelin levels. Given the forecasted levels of Capelin for the next two years, the prospects for cod stock growth appear limited. The Newman Sound pre-recruit index suggests that cohorts from 2018 to 2020 will be weaker than those in the past ten years and the pre-recruit index is well below the mean of those in the 25-year time series. The stock is being assessed using an integrated model (Northern Cod Assessment Model, NCAM), which allows quantification of uncertainty in estimated and projected stock status. The estimate of Spawning Stock Biomass (SSB) in 2021 is 411 kt (95% CI = 307–549 kt). SSB currently remains in the critical zone, at 52% (95% CI = 39–69%) of the Limit Reference Point (LRP). The stock has remained at about the same level since 2017. Natural mortality rate (M) estimated from NCAM for ages 5+ for 2020 was 0.51 (95% CI = 0.30–0.89). The average M over the last 10 years was 0.39 (range = 0.29 to 0.63). The fishing mortality rate (F) estimated from NCAM for ages 5+ is currently low, and for 2020 was 0.018 (95% CI = 0.014–0.024). The average F over the last 10 years is 0.02 (range = 0.014 to 0.028). Recruitment (age 2) estimated from NCAM increased from the lowest estimated levels of 34 million fish in 1995 to an average of 314 million per year for cohorts from 2015 to 2019. This recent average is 25% of the pre-collapse period of the 1980s. A one year projection from NCAM with catch ranging from zero to 1.3 times (15,360 t) the model estimated catch for 2020 (11,816 t) indicated that the probability that SSB will reach the LRP by 2022 is <0.02. The probability of the stock being greater in 2022 than in 2021, across all catch scenarios examined ranged from 0.52 to 0.59. The calculation of the Harvest Decision Rule (HDR) for this stock in accordance with the Northern Cod Rebuilding Plan indicates removals for 2021 of 12,999 t for stewardship fishery catch. When accounting for the recreational fishery these removals are likely to fall at, or above, the upper range of catch scenarios examined. Consistency 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.