Research Document - 2009/097

Precautionary reference point estimates for northern Gulf of St. Lawrence (3Pn4RS) cod (Gadus morhua) and methods for their calculation

By D.E. Duplisea and A. Fréchet

Abstract

Six biomass limit reference points are estimated for northern Gulf of St. Lawrence (nGSL) cod. Five of these points are based on stock-recruit data while the sixth point is based purely on the concept of the minimum observed biomass from which there has been a recovery. In addition, two new methods for estimating reference points from stock-recruit data are introduced and estimated for nGSL cod. These new points should be evaluated on a variety of data sets, including simulated data and peer review before acceptance, though we introduce them here to place them in the context of other established methods. We conclude that for this stock, two of the six estimates can be considered credible for the stock using the 1974-2009 cohort reconstruction model output and place the biomass limit reference point at about 140,000 t spawning stock biomass (SSB) (this value was used in the 2009 assessment) We further suggest an upper stock reference point at about 200,000 t SSB which is a point above which there is little evidence of increased recruitment for an increase in SSB.

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