Specification and conditioning of the hake OMP2018 Reference Set models

Ross-Gillespie, Andrea; Butterworth, Doug S

Specification and conditioning of the hake OMP2018 Reference Set models

Report

2018-11

Abstract

The specification and conditioning results of the nine 2018 Reference Set Operating Models are provided. These nine models consist of a cross of three different assumptions regarding the stock-recruitment relationship (one Ricker and two Beverton-Holt) and three assumptions regarding the central year in which the catch shifts from primarily M. capensis to primarily M. paradoxus. Estimates of current depletion for M. paradoxus range from 0.26 to 0.39 for the (generalised) Ricker, and from 0.15 to 0.41 for Beverton Holt stock-recruitment models. Current depletion for M. capensis ranges from 0.68 to 0.74 for Ricker, and from 0.08 to 0.76 for Beverton-Holt models. The Beverton-Holt based OMs generally reflect worse fits than the Ricker-based OMs in terms of the negative log-likelihood, and many of the Beverton-Holt models show little effect of changes in spawning biomass on expected recruitment. M. paradoxus is consistently estimated to be above BMSY . M. capensis is above BMSY except for the runs Beverton-Holt that produce a very flat biomass trajectory where biomass has little impact on recruitment.

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