Science Advisory Report  2012/073

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

Summary

• As of December 15, 2012, 4,054 mt of the 4,200 mt Total Allowable Catch (TAC) for 2012 had been landed.
• Although the standardized catch per unit effort (CPUE) index, an index of abundance, increased slightly, while the Gulf and survey CPUE indices decreased, catch rates remain relatively stable overall and slightly below average for the past decade.
• The total biomass estimate (28,028 +/- 4,560 mt) decreased by 8% in 2012 and has decreased by 38% since the peak in 2009.
• The spawning stock biomass point estimate (14,763 mt) decreased by 12% in 2012, but remains slightly above the upper stock reference of 14,558 mt (i.e., in the Healthy Zone).
• The precautionary reduction in the TAC for 2012 (9%) helped to offset decreased biomass, so female exploitation (19%) remained below the 20% removal reference.
• Recent trends in the research survey coefficient of variation index (low) and the commercial fishing area index (stable) suggest that the stock is relatively evenly distributed on the fishing grounds.
• The moderately abundant 2007-2008 year classes continue to support the fishable and spawning stock biomass in 2012 and 2013.
• Length frequency distributions from survey and commercial gear suggest that succeeding year classes (>2008) are not very abundant. This is consistent with the recent values for the belly bag index, which suggest poor recruitment to the 2009-2011 year classes.
• Total and spawning stock biomass are likely to remain relatively stable in 2013, as the 2008 year class fully undergoes sex transition to 5-year old females. Given the expected reduction in the 2007-2008 year classes, and the evidence of low abundance of succeeding year classes, biomass is expected to decline in 2014.
• Spring sea surface temperatures and survey bottom temperatures (June) remained high in 2012 relative to the long term average, which could have a negative effect on juvenile recruitment and will be a concern for the stock if these trends continue.
• Given the anticipation of the recruitment of the relatively abundant 2008 year class to spawning stock biomass in 2013, biomass is expected to remain relatively stable and a status quo TAC is not expected to exceed the removal reference. However, a TAC reduction would promote higher total and spawning stock biomass in 2013 realized from the full recruitment of the 2007 and 2008 year classes to the female portion of the stock, increasing the likelihood of strong recruitment if conditions are suitable.

This Science Advisory Report is from the December 4, 2012 regional peer review meeting on the Assessment of Eastern Scotian Shelf Shrimp. Additional publications from this process will be posted as they become available on the Fisheries and Oceans Canada Science Advisory Schedule.

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