Science Advisory Report  2012/004

Reference points for redfish (Sebastes mentella and Sebastes fasciatus) in the northwest Atlantic

Summary

• Approaches were investigated for developing limit reference points (LRP’s) for five Atlantic redfish stocks based on the best science available at the present time.  LRP’s from the Bayesian surplus production model (BSP) were accepted for four stocks, while an empirical reference point was accepted for the fifth stock.
• The LRP consistent with the default reference points in the DFO precautionary approach (PA) policy suggests using 40% Bmsy (or 20% of the maximum unfished biomass) for the stocks modeled using the Schaefer BSP) approach.
• The Unit 3 LRP was determined from empirical methods in the survey because of insufficient signal in the survey and catch for the BSP model fitting.
• The LRP values (and stock biomass expressed as a fraction of the LRP) in 2010 or 2011 are: 2+3K S. mentella – 116 kt (0.14); Unit 1+2 S. mentella – 233 kt (0.08); 2+3K S. fasciatus – 29 kt (0.28); Unit 1+2 S. fasciatus – 148 kt (0.44 in 2011); and Unit 3 S. fasciatus – 29 kt (3.2).
• Growth status (increasing, unchanged, decreasing) was determined by comparing the most recent catch to the replacement yield from the production model: 2+3K S. mentella – increasing; Unit 1+2 S. mentella – decreasing; 2+3K S. fasciatus – increasing; Unit 1+2 S. fasciatus – increasing; Unit 3 S. fasciatus – increasing (smoothed empirical trend).
• It is expected that the current reference points will stand until some important change in information necessitates a re-evaluation of reference points. Issues identified which merit further investigation include particularly survey catchability (reservations were expressed about q>1).
• Work shows that the fish in Laurentian fan (shelf edge) area are predominantly S. fasciatus, and previous DFO work shows that S. fasciatus in this area is part of the Grand Bank (3LNO) population.

This Science Advisory Report is from the October 25-27, 2011 Precautionary approach reference points for Atlantic Redfish (Sebastes fasciatus, Sebastes mentella) populations. 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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