Science Advisory Report 2009/032

Assessment of 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 2008 were 2,755 t. The spring spawner TAC was 2,500 t.
• The cumulative index of the opinions of harvesters on the abundance of spring herring in 2008 was the lowest in the time series that starts in 1987.
• Mean gillnet catch rate in 2008 was higher than 2007, but similar to the values from 2004 to 2006. The index has been declining since 1997 and remains at a low level in the series that starts in 1990.
• The 2008 acoustic index was one of the lowest in the series that starts in 1994.
• The estimated exploitation rate was below the reference level in 2008.
• The abundances of year-classes after 1991 have been average or below average.
• Overall spawning stock biomass has declined since 1995 and remains at a low level since 2004.
• The current estimate of age 4+ biomass (20,300 t) is below the limit reference point (LRP, 22,000 t). At this level of biomass, the precautionary approach requires that removals from the stock should be kept to the lowest level possible.
• Even in the absence of any removals of the spring spawning component, there is a 65% probability that the biomass in 2010 will be below the LRP. Catch options less than 1,100 t would provide a low probability (<25%) of a decline in biomass from 2009.

Fall Spawner Component

• Reported landings of the fall spawner component in both the spring and the fall fisheries in 2008 were 41,471 t. The fall spawner TAC was 68,800 t.
• The cumulative index from the opinions of harvesters on the abundance of fall herring has been decreasing since 2006, although the index is higher than it was prior to 2000.
• Mean gillnet catch rate in 2008 was lower than the previous three years.
• The exploitation rate in 2008 was below the F0.1 reference level.
• Estimated recruitment at age 4 was above average from 1999 to 2005, and again in 2008.
• Overall, the stock remains at a high level of abundance relative to the late 1970’s and early 1980’s.
• The 2009 beginning-of-year spawning stock biomass is estimated to be about 285,500 t, above the upper stock reference (USR) level of 172,000 t.
• For 2009, a catch option of 65,500 t corresponds to a 50% chance that F would be above the F_0.1 removal rate. There is a low probability (< 25%) of a decline in biomass from 2009 for catch options less than 33,000 t.

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