Science Advisory Report 2010/023

Assessment of Atlantic herring in the southern Gulf of St. Lawrence (NAFO Div. 4T)

Summary

Spring Spawner Component

• Reported landings of the spring spawner component in both the spring and the fall fisheries in 2009 were 1,667 t. The spring spawner TAC was 2,500 t.
• The opinions of fixed gear harvesters from the telephone survey was that abundance of spring herring in 2009 was higher than 2008.
• Mean gillnet catch rate in 2009 was higher than 2008, but similar to values since 2004. The index has been declining since 1997 and remains at a low level in the series that starts in 1990.
• The 2009 acoustic index was higher than 2008 but remains low in the series that starts in 1994.
• Overall spawning stock biomass has declined since 1995 and remains at a low level.
• The current estimate of age 4+ spawning stock biomass (SSB) of 28,200 t is above the limit reference point (LRP) of 22,000 t but below the upper stock reference (USR) of 54,000 t. When the SSB declines below the USR, a harvesting strategy compliant with the Precautionary Approach (PA) would reduce the exploitation rate to promote stock growth to above the USR.
• The estimated exploitation rate in 2009 was 8% and below the removal reference level of 27%. The realized reduced exploitation rate on this component since 2007 is consistent with the PA.
• The abundances of recruiting year-classes (at age 4) after the 1991 year-class have been average or below average.
• A catch option of about 1,100 t in 2010 would provide a 50% probability of at least a 5% increase in biomass in 2011.
• Projections for the fisheries over the next two years (2010-2011) show that the probability of a 5% increase in biomass from 2010 to 2012 is 62% with annual catches of 2,000 t or less in 2010 and 2011.

Fall Spawner Component

• Reported landings of the fall spawner component in both the spring and the fall fisheries in 2009 were 46,747 t. The fall spawner TAC was 65,000 t.
• The opinion of fixed gear harvesters from the telephone survey is that the abundance of fall herring has been decreasing since 2006, with a slight increase in 2009.
• Mean gillnet catch rate in 2009 was slightly higher than 2008 but was lower than the previous three years.
• The exploitation rate in 2009 was 19%, below the F_0.1 reference level of 25%.
• Estimated recruitment at age 4 was above average from 1999 to 2005, and again in 2008 and 2009.
• Overall, the stock remains at a high level of abundance relative to the late 1970’s and early 1980’s.
• The 2010 beginning-of-year spawning stock biomass is estimated to be about 307,400 t, above the upper stock reference (USR) level of 172,000 t.
• For 2010, a catch option of 67,700 t corresponds to a 50% chance that exploitation rate would be above the reference removal rate. There is a low probability (< 25%) of a decline in biomass from 2009 for catch options less than 42,000 t.
• Projections for the fisheries over the next two years (2010-2011) show that the probability of a decline in biomass of more than 10% from 2010 to 2012 is low (£10%) with annual catches of 50,000 t or less, rising to nearly 100% with catches of 60,000 t or more.

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