Science Advisory Report 2023/036
Stock assessment of Gulf of St. Lawrence (4RST) Atlantic halibut in 2022
- Atlantic halibut landings have been increasing since the early 2000s and have reached the highest values since 1960. For the 2021-2022 and 2022-2023 management years, preliminary landings are 1,526 t and 1,407 t respectively.
- The biomass indices of commercial-sized Atlantic halibut (greater than 85 cm) from trawl surveys in 2021 and 2022 are among the highest in historical series.
- Abundance indices of Atlantic halibut pre-recruits (65 to 85 cm) from trawl surveys show high values since the mid-2000s.
- The catch per unit effort of the Atlantic halibut in the directed longline fishery increased from the early 2000s to the mid-2010s. Since then, it has been high and stable at about 450 kg per 1,000 hooks.
- The average size and weight of landed Atlantic halibut are increasing since 2006.
- Adjustment of a delay-difference type assessment model, integrating DFO monitoring, longline survey and capture-mark-recapture, shows that the biomass of the commercial-sized stock is growing to reach 94,482 t in 2022.
- A limit reference point is set at 40% of the theoretical biomass at the maximum sustainable yield (BMSY), i.e., 25,291 t. A upper stock reference point (USR) is proposed at 80% of the BMSY, i.e., 50,582 t, and would place the stock in the healthy zone of the precautionary approach. However, the results of the model are sensitive to the adjustment parameters chosen.
- The exploitation rates estimated by the model have been low for 15 years and are consistent with the values observed from capture-mark-recapture work and the relative exploitation rates obtained from the minimum trawlable biomass of DFO surveys.
- The model's 2-year projections show that a significant increase in removals is not expected to cause a decrease of the stock biomass, which would remain within the healthy zone under the proposed USR. These projections are robust to different modelling scenarios.
This Science Advisory Report is from the March 6-7, 2023 regional peer review meeting on the Assessment of the Gulf of St. Lawrence (4RST) Atlantic Halibut stock. 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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