Science Advisory Report 2021/017
Assessment of the Gulf of St. Lawrence (4RST) Greenland halibut stock in 2020
- The total allowable catch (TAC) for the Gulf of St. Lawrence Greenland halibut stock was gradually reduced by 50% between the 2017-2018 and 2020-2021 fishing seasons to stand at 2,250 t. Preliminary landings for 2020-2021 totaled 1,330 t.
- For the Western Gulf and Esquiman sectors, fishing effort and landings decreased from 2019 to 2020 and reached some of the lowest values in each of the series. The situation was different for the North Anticosti sector which, after being abandoned from 2015 to 2017, experienced a resumption of activities. Between 2019 and 2020, the effort remained fairly stable while landings increased.
- From 2019 to 2020, the commercial fishery performance indices were stable for the Western Gulf and Esquiman sectors and increased in the North Anticosti sector. The indices of the three sectors are below the average of their respective series.
- The composition of landings changed markedly between 2018 and 2019. The average fish size decreased by 2.5 cm to 45.6 cm (average of 47.0 cm). The proportion of fish smaller than the minimum size of 44 cm increased to 30% (average of 17%). In 2018 and 2019 landings were made up of nearly 85% females (average of 80%). Data for 2020 were partial due to the health measures related to the pandemic.
- According to scientific surveys by DFO and mobile sentinel program, the abundance and biomass indices of Greenland halibut generally showed a downward trajectory from the end of the 2000s to 2019. These indices increased slightly between 2019 and 2020 to levels well below the peaks of the 2000s. This increase is caused by the arrival of the strong 2018 cohort. This cohort is showing a normal growth rate and should start recruiting to the fishery in 2024.
- The cohorts expected to recruit to the fishery in 2021 and 2022 are of average to low abundance.
- At the Gulf level, the exploitation rate indicator decreased from 2019 to 2020 and remained close to the series average.
- The Gulf of St. Lawrence is undergoing major changes: deep waters are warming and becoming depleted of oxygen. These changes can lead to habitat degradation, decreased growth, increased natural mortality and can negatively affect the productivity of Greenland halibut. In addition, changes in the structure of the community (high abundance of redfish and low abundance of shrimp) can modify the interactions of competition for food resources or for habitat. Current environmental conditions and climate projections suggest that the situation is likely to worsen.
- According to the precautionary approach under development, the stock status indicator was on a downtrend with a decline of over 60% between 2008 and 2017, moving from the healthy zone to the cautious zone. The indicator stabilized from 2017 to 2020 and is midway between the limit reference point and the upper stock reference point. Under these conditions, a reduction in catches below recent levels could reduce the exploitation rate and help increase the stock. However, the unfavorable environmental conditions for Greenland halibut that prevail in the Gulf of St. Lawrence could be determining factors in the trajectory of the stock's abundance.
This Science Advisory Report is from the regional advisory meeting of February 23-24, 2021 on the Assessment of the Gulf of St. Lawrence (4RST) Greenland halibut. 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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