Science Advisory Report 2021/029
Assessment of the northern contingent of Atlantic Mackerel (Scomber Scombrus) in 2020
- Nominal landings were updated for the years 2017-2020 and were 9786 t, 10 964 t, 8623 t, and 7772 t respectively. The TACs were 10 000 t from 2017-2018 and 8000 t from 2019-2020. Landings during these years occurred primarily in the Gulf of Saint Lawrence (NAFO 4RST) and off the northeast coast of Newfoundland (NAFO 3K).
- Recent genetic analyses confirmed previous studies that the Northwest Atlantic mackerel stock is distinct from the Northeast Atlantic stock. These analyses also supported the previously established distinction between the northern and southern spawning contingents of the Northwest Atlantic stock. Genetic results showed some mixing of southern contingent mackerel in Canadian waters as well as northern contingent mackerel in U.S. waters.
- A fine-scale analysis of recruitment variability showed that a spatio-temporal match between mackerel larvae and their preferred food as well as optimal population structure and dynamics (maternal condition, SSB, age-structure) benefits recruitment.
- The annual egg survey did not occur in 2020 due to restrictions incurred by the global Covid pandemic. The absence of this survey index for one year did not prevent the use of the stock assessment model to estimate stock status.
- The Spawning Stock Biomass (SSB) of the northern contingent of Atlantic mackerel is was at the lowest value estimated and was at 58% of the Limit Reference Point (LRP) in 2020. The stock has been near or below the LRP for the past decade according to the Precautionary Approach.
- The last notable recruitment event was in 2015, while the stock was in the Critical Zone, but fish belonging to this cohort represented about 7% of the SSB in 2020. There was no sign of any notable recruitment event in recent years.
- The estimated fully selected exploitation rate (fish aged 5-10+) in 2020 was 74%, above the reference level of 51% (F40%). The fishery was concentrated on fish aged 2-5 (exploitation rate of 56%). There are currently very few fish older than 5 years old (<1%).
- Depending on the TAC (0-10 000 t) and recruitment projection, the probability of the SSB exiting the Critical Zone by 2023 varies from 29% (TAC = 10 000 t) to 58% (TAC = 0 t). These projections also indicate that the probability SSB in 2023 being greater than SSB in 2021 varies from 39% (TAC = 10 000 t) to 92% (TAC = 0 t).
- The SSB in 2020 was the lowest ever estimated and has been in or near the Critical Zone for over 10 years. According to the Precautionary Approach, removals from all sources should be as low as possible to allow rebuilding. Rebuilding the stock will also require rebuilding the age structure of the stock which has been eroded by overexploitation.
This Science Advisory Report is from the February 25-26 and March 3, 2021 regional advisory meeting on the Assessment of the northern contingent of Atlantic Mackerel (Scomber scombrus). Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.
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