Science Advisory Report  2011/029

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

Summary

• Point estimates of the 2010 total and spawning stock biomasses decreased from the near-record high 2009 estimates, but remain above the average values of the 2000-2009 high-productivity period.
• In 2010, consistent decreases in all three Catch per Unit Effort (CPUE) based indices, coupled with decreases in the area of highest catch-rates, provide compelling evidence of a biomass downturn.
• The abundance of Age 4 male shrimp increased in 2010.  An abundance of Age 4+ males in 2009, probably representing late maturing males from the 2001 year class, provided females to the spawning population in 2010 and should continue to do so in 2011. Taken together, these indices suggest good recruitment to the spawning stock biomass in 2011.
• Total (13.2%) and female (16.8%) exploitation indices increased but remain below the 20% limit reference point.
• Indices of dispersion suggest that shrimp are beginning to aggregate on the fishing grounds, as would be expected during a biomass downturn.
• Indicators of shrimp size continue towards larger maximum, female and sex-transition sizes and lower counts.
• The continuation of a Total Allowable Catch (TAC) of 5000 mt for 2011 is supported by the current assessment, with the proviso that a TAC reduction may be required for 2012 if exploitation indices approach or exceed 20% in 2011. A moderate decrease in the TAC would, of course, decrease the likelihood of over-running the exploitation limit reference point in 2011 should the biomass downturn continue.

This Science Advisory Report has resulted from a Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, Regional Advisory Meeting of December 17, 2011 on the Assessment of 4VW Shrimp. Additional publications from this process will be posted as they become available on the DFO Canadian Science Advisory Secretariat website.

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