Science Advisory Report  2011/012

Stock Assessment of Atlantic Halibut of the Gulf of St. Lawrence (NAFO Division 4RST) for 2009 and 2010

Summary

• Preliminary landings as of December 31, 2010 were 626 t, or 4% more than the total allowable catch (TAC) for the 2010-2011 fishing season that was set at 600 t. These landings represent the second highest value since the 1960s. The 2010-2011 TAC was increased by 26% while the minimum legal catch size was increased from 81 to 85 cm. Reported landings in 2009-2010 reached 672 t, exceeding the 475 t TAC by 40%. They are the highest in 45 years.
• In 2009 and 2010, approximately 80 t were landed as by-catches in the gillnet fishery. Over 80% of these catches were from the Greenland halibut fishery. Data from at-sea observers indicate that these catches are composed largely of individuals smaller than the minimum legal size that are neither landed nor counted. Thus, the mortality of fish discarded at sea by turbot fishermen is presumed very high (over 50%).
• During the 2000s, the abundance and biomass indices from the scientific trawl surveys showed a sharp increase in the Gulf, both for pre-recruits (<minimum legal size) and for recruits (≥ minimum legal size). Maximum values were observed between 2007 and 2010. The range of sizes measured is substantial. The median size is higher and variable in the north (60 to 75 cm) than in the south (50 cm) of the Gulf.
• Catches per unit effort calculated for the directed Atlantic halibut fishery using longlines have consistently increased since the early 2000s, reaching their maximums in 2009 and 2010.
• In 2010, longline catches recorded at sea showed that pre-recruits are still abundant (⅓ in numbers) whereas the proportion of halibut larger than 130 cm was about 10%.
• The mean modal size, measured at sea and dockside, was around 85 cm for the 1997-2009 period. The majority of females landed were immature since the length at which 50% of females are mature is 130 cm.
• Over the past 10 years, all indices have increased significantly. Under these conditions, considering a TAC increase of around 20%, total over the next two years, abundance indices should still continue to increase.
• Given the significance of Atlantic halibut discards at sea in some fisheries, in particular immature individuals, management measures should be implemented to account for and reduce these discards in order to protect the spawning stock’s growth potential. In this regard, a more accurate method for assessing the magnitude of these discards should be developed.

This Science Advisory Report has resulted from a Fisheries and Oceans Canada, Canadian Science Advisory Secretariat Quebec Regional Advisory Process of February 16, 2011 on Stock Assessment on Atlantic Halibut in the Gulf of St. Lawrence (4RST). Additional publications resulting from this process will be posted as they become available on the DFO Science Advisory Schedule.

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