Science Advisory Report  2012/027

Projections of the Atlantic Halibut Population on the Scotian Shelf and Southern Grand Banks (NAFO Divisions 3NOPs4VWX5Zc)

Summary

• Based on model projections, 3NOPs4VWX5Zc Atlantic halibut is in a productive period due to high recruitment. The spawning stock biomass is expected to increase, and there is little risk in harming the productivity of the stock at harvest levels < 4,000 t.
• The probability of exceeding the target removal reference, Fref=0.2, is low (<0.1%) at current catch levels, and the probability decreases as the population grows. Projections to 2014 show that the probability of exceeding the limit removal reference, Flim=0.36, is also low (<1%) at a catch of 3,400 t per year.
• A catch of 1,850 t in 2012 (2012/2013 total allowable catch, TAC) is expected to result in a fishing mortality (F) of 0.15 and a 9.5% percent increase in biomass in 2013. A catch of 2,127.5 in 2012 (15% increase to the TAC) is expected to result in an F of 0.17 and a 7% percent increase in biomass.   
• In a comparison of biomass at maximum sustainable yield (Bmsy) and fishing mortality at maximum sustainable yield (Fmsy) generated using a Beverton-Holt stock-recruit model versus a Ricker model, Bmsy and Fmsy differed by a factor of 2, demonstrating the sensitivity of these reference points to model assumptions.
• The 2011 population spawning stock biomass is projected to be above Bmsy regardless of which stock-recruit model is used. 
• Several sources of uncertainty have not been incorporated into the projections, for example, uncertainty in natural mortality, selectivity to the fishing gear, and the stock-recruit parameters.

This Science Advisory Report is from the Maritimes regional science advisory meeting of November 22, 2011 to review the Assessment of 4X5Y Haddock and Projections for 3NOPs4VWX+5Zc Atlantic Halibut.  Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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