Terms of Reference

Assessment of the northern contingent of Atlantic Mackerel (Scomber scombrus)

Regional Peer Review - Quebec Region

February 20-22, 2023
Mont-Joli, QC

Chairperson: Marie-Julie Roux

Context

Atlantic Mackerel (Scomber scombrus) are a highly migratory transboundary species with two distinct spawning contingents in the Northwest Atlantic. The southern contingent has historically spawned in the Mid-Atlantic Bight from April to May whereas the northern contingent spawns primarily in the Southern Gulf of St. Lawrence in June and July. Both contingents overwinter in deeper warmer waters off the continental shelf. The U.S. fishery takes place during the winter along the New England coast and lands both contingents, whereas landings in Canadian waters are thought to consist entirely of mackerel from the northern contingent. Canada evaluates the northern contingent every two years and as of the last assessment in 2021, this stock was still in the Critical Zone according to the Precautionary Approach.

In 2022, Fisheries Management closed both the commercial and bait fishery for the first time. Mackerel were previously harvested commercially and for bait across the Atlantic Provinces and Quebec in an open competitive fishery using a variety of gear types (gillnets, mechanical jiggers, seines, weirs, and traps). Mackerel are also harvested through a popular recreational fishery that remained open, but for which there a daily possession limit of 20 fish per person per day since May 2021. While each regional fishery implements its own license conditions, mackerel are managed on a national level. Representatives from the industry, Indigenous Groups, and other stakeholders participate in a “Rebuilding Plan Working Group” organized by Fisheries Management.

In contrast to Canada, the U.S.A. assesses both spawning contingents as one unit. An update of their scientific advice was made in 2021. The U.S.A concluded that the stock was overfished and overfishing was occurring.

The spawning stock biomass, fishing mortality, and recruitment of northern contingent mackerel are estimated by DFO using a custom statistical catch-at-age model. This model fits to an annual egg index, catch-at-age and so-called censored catches. Specifically, the uncertainties in unaccounted for Canadian catch as well as catch by the fishery in the U.S.A. are accounted for explicitly in the model through the estimation of catch between the recorded landings and an estimate of maximum fishery removals. 

The last assessment of mackerel in Canada took place in February 2021. The stock was below its Limit Reference Point (LRP) and is now subject to a rebuilding plan under the Fish Stocks Provisions (FSP). The Fisheries Resource Management Branch has requested scientific advice on Atlantic Mackerel for the 2023 and 2024 fishing seasons, including an assessment of stock status and scientific information to inform the rebuilding plan; relevant information on the biology of the fish and environmental conditions affecting the stock, information on whether habitat loss or degradation has occurred and contributed to the stock’s decline, and an assessment of the time (Tmin) the stock would take to rebuild to a rebuilding target in the absence of all fishing (F=0).

Objectives

Provide scientific advice on the status of the northern contingent of Atlantic Mackerel for the 2023 and 2024 fishing seasons and provide information that will feed into the rebuilding plan. This advice will include:

• Stock structure information and definition of the assessed unit: an update of mackerel genomics describing the population structure across the Atlantic and within the Northwest Atlantic.
• An assessment of the potential magnitude and trends of mackerel consumption by individual predators (e.g., Atlantic bluefin tuna, northern gannets, spiny dogfish and grey seals).
• An assessment of the relative importance of the southern Gulf and adjacent ecosystems for mackerel spawning, including:
• A summary of existing knowledge on mackerel spawning across Atlantic Canadian waters.
• Results of the 2021 and 2022 western and southern Newfoundland egg survey.
• An update on the status of Atlantic mackerel, including:
• A summary of fishery statistics up to the 2022 fishing season (Canada and U.S.A.).
• A summary of the biological and fishery data used as input into the stock assessment model.
• An update of the egg survey index.
• A presentation on the results of the stock assessment model (estimates of fishing mortality, spawning stock biomass, abundance at age) as well as spawning stock biomass projections for the years 2023-2025 under different TAC scenarios.
• An update of stock status with respect to the Precautionary Approach and agreed upon reference points.
• Specific elements to inform the update of the rebuilding plan:
  • Estimation of a Tmin, which is the time the stock would take to rebuild to a rebuilding target in the absence of all fishing (F=0).
  • A summary of available knowledge on the ecosystem considerations including variations in life history parameters, species interactions (e.g., predators, prey) and environmental conditions that affect growth, survival, and recruitment of mackerel across their distribution, and how they are accounted for in the assessment and how they can affect rebuilding.
  • Describe probable causes of the stock’s decline, including whether habitat degradation or loss has occurred and whether it has contributed to the stock’s decline.
• Identification and prioritization of research projects to be considered for the future.

Expected Publications

• Science Advisory Report
• Research Document
• Proceedings

Expected Participation

• Fisheries and Oceans Canada (DFO) Science and Fisheries Management
• Fishing industry
• Provincial government representatives
• Aboriginal Communities / Organizations
• Academia
• Environmental NGOs