Research Document - 2012/171

Equilibrium estimates of Fmsy and Bmsy for 3Pn4RS cod

By D.E. Duplisea

Abstract

Fmsy and Bmsy reference points for northern Gulf of St Lawrence (3Pn4RS) cod were estimated by projecting an age structured model to equilibrium under different F with various assumptions about stock-recruitment relationship and natural mortality resulting in 21 a priori reasonable scenarios. A preferred run was selected from the 21 different scenarios based on criteria related to consistency with previously estimated reference points as well which projection best represented the long-term (equilibrium) potential production of the stock accounting for uncertainty in natural mortality. The selected run was based on projection using a previously established fit of the hockey-stick stock-recruitment model combined with stochastic natural mortality ranging from 0.2-0.4 and a mean of 0.25. The Bmsy value from the preferred run was selected as the biomass target reference point (209,000 t) while ⅔Fmsy (0.16) was selected as the F strategy in the healthy zone recognising the F should have a low probability of exceeding Fmsy. The precautionary approach framework suggested for this stock conforms to international norms for PA development

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