Science Advisory Report  2012/001

Assessment of Northern Shrimp on the Eastern Scotian Shelf (SFAs 13-15)

Summary

• The point estimate of the 2011 spawning stock biomass (16,823 mt) decreased for the second consecutive year from the near-record high 2009 estimate, but remains above the upper limit reference point of 14,558 mt (i.e., in the Healthy Zone).
• Because the relative decrease in the point estimate of spawning stock biomass exceeded the Total Allowable Catch (TAC) reduction from 2010 to 2011, female exploitation rose to 20.3%, which is slightly above the removal reference point of 20%.  
• The abundance of Age 2 shrimp decreased in 2011, which is consistent with the low belly-bag index in 2010.
• The abundant 2007 year class increased the index of abundance of Age 4 male shrimp in 2011, which is expected to provide good recruitment to the spawning stock biomass in 2012.
• For the past two years, a large proportion of the TAC (32-41%, assuming the TAC is caught in 2011) has been taken during the egg-bearing period, which risks a loss of reproductive potential by removing egg-bearing females before spawning.
• Ecosystem indicators (high temperatures and reductions in the abundance of sympatric species) suggest that conditions are currently unfavourable for shrimp.
• Despite generally favourable indicators of abundance, the continuation of the biomass downturn in 2011, coupled with decreases in shrimp size, poor recruitment, a temporal shift in fishing effort, and unfavourable ecosystem indicators, suggest that a TAC reduction would be prudent for 2012 to minimize the likelihood of bringing the stock below the upper limit reference point or of further exceeding the removal reference point. 

This Science Advisory Report has resulted from a Fisheries and Oceans  Canada, Canadian Science Advisory Secretariat Maritimes Regional Advisory Meeting of December 5, 2011 on the Assessment of Eastern Scotian Shelf Shrimp; Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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