Science Advisory Report  2015/004

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

Summary

• As of November 17, 2014, 4,041 mt of the 4,500 mt Total Allowable Catch (TAC) for 2014 had been landed.
• Both the Gulf and Standardised catch per unit effort (CPUE) indices decreased by approximately 30%, which was a divergence from the survey CPUE, which remained high.
• Based on the survey, the total biomass estimate of 39,381 (95% confidence interval 32,435-46,328) mt remained approximately stable at a high level in 2014, decreasing only 1.5% from 2013.
• The spawning stock biomass (SSB, females) point estimate (20,359 mt) remained approximately stable well above the upper stock reference (USR) of 15,558 mt, decreasing only 1.5% from the 2013 value.
• The 18% increase in the TAC for 2014 (to 4500 from 3800 mt in 2013) to capitalise on the high fishable biomass of the abundant 2007-2008 year classes was sufficiently precautionary to maintain female exploitation at 15%, below the 20% removal reference for this stock.
• The moderately abundant 2007-2008 year classes continue to provide a detectable signal in the trawl survey and commercial catches, and make up most of the high fishable and spawning stock biomass, supplemented by less abundant subsequent year classes.
• Cohort tracking in length frequency distributions from survey and commercial samples corroborates the low belly-bag indices from 2010-2013 in predicting low contributions of the 2009-2012 year classes to fishable and spawning stock biomass.
• The very high value of the 2014 belly-bag index suggests strong juvenile recruitment from the 2013 year class, which should begin to recruit to the fishable biomass in 2016 if survival conditions are suitable.
• As predicted in recent assessments, the stock is beginning to decline, as the 2007-2008 year classes approach the end of their expected lifespan.
• Although cooling spring sea surface temperatures and very low cod recruitment suggest conditions will be favourable for shrimp, the increase in abundance of shrimp predators, warm bottom temperatures, and continued low or declining abundance of sympatric coldwater species suggest the opposite.
• Although the stock is expected to continue to gradually decline in 2015, the high fishable and spawning stock biomass in 2014 suggests that a status quo TAC will not exceed the removal reference in 2015. However, given the small size of the 2009-2012 year classes, reactive TAC reductions will be required if the stock declines towards to the Cautious Zone.

This Science Advisory Report is from the November 27, 2014, Assessment of Eastern Scotian Shelf Shrimp. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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