Science Advisory Report 2018/035

Assessment of the Greenland Halibut stock in the Gulf of St. Lawrence (4RST) in 2017

Summary

• For the 2017-2018 fishing season, landings of Greenland Halibut reached 1,665 t (preliminary 31 December) for a fishing allocation of 3,750 t (4,500 t TAC). These landings are well below the 3,358 t average for the last 10 years for the period May 15 to December 31.
• Across the Gulf, gillnet effort targeting Greenland Halibut has been decreasing and is below the series average since 2015. This reduction is related to the abandonment of the northern Anticosti sector and a drop in effort in the Esquiman sector. The effort has remained stable in the western Gulf sector since 2015 and accounted for more than 80% of the total fishing effort deployed in 2017.
• Between 2016 and 2017, the performance index in the commercial fishery (CPUE) over the entire Gulf decreased by 36% and is now below the 1999-2016 series average. Of the three sectors, the western Gulf suffered the largest decline in the index, equivalent to more than 50% compared to historical highs of 2015 and 2016. In the northern Anticosti and Esquiman sectors, the index has been declining since 2009 and is below the average of each series since 2013.
• In 2017, the biomass indices for fish over 40 cm in the DFO and sentinel surveys decreased by 44% and 30% respectively compared to 2016 and are below the average of their respective series. These indices follow a downward trend since more than 10 years.
• At the scale of the Gulf, the 2017 exploitation rate indicator remains close to the time series average despite low landings. However, this indicator is increasing in the western Gulf sector.
• The strong cohorts of 2012 and 2013 grew slower than average and their recruitment to the fishery is uncertain. The abundance of the 2014 cohort is within average while the abundance of the 2015 and 2016 cohorts is low.
• Fish of the 2012 to 2015 cohorts have below-average condition indices. The condition index for the 2016 cohort at 1 year is above average.
• An upper stock reference point (USR) of stock status was proposed in accordance with the precautionary approach. According to this USR, the status of the Greenland Halibut stock from the Gulf of St. Lawrence would be in the cautious zone since two years.
• The Gulf of St. Lawrence ecosystem is undergoing significant changes in recent decades. Deeper water layers are warming up and becoming poorer in oxygen. These factors can lead to habitat loss and reduced growth for Greenland Halibut. Deepwater temperatures will remain high for the coming years. The arrival of three very strong cohorts (2011-2013) of redfish increases interspecific competition with Greenland Halibut, which occupies a similar ecological niche.
• The short-term outlook for the Greenland Halibut stock in the Gulf of St. Lawrence is concerning given ecosystem changes, poor recruitment, decreasing indices of abundance and biomass of fish over 40 cm, and the reduction in the fishery performance index. As a result, withdrawals should be reduced for the 2018-19 fishing season to avoid an increase in the exploitation rate.

This Science Advisory Report is from the meeting of March 13, 2018 on the Assessment of Greenland Halibut stock in the Gulf of St. Lawrence (4RST). 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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