Research Document - 2011/135
Stock Assessment and Recovery Potential Assessment for Quillback Rockfish (Sebastes maliger) on the Pacific Coast of Canada
By K.L. Yamanaka, M.K. McAllister, M.-P. Etienne, and R. Flemming
Abstract
The Committee On the Status of Endangered Wildlife In Canada (COSEWIC) designated Quillback Rockfish in British Columbia as threatened in November 2009. The rationale for this designation are their inherent low productivity due to longevity (95 years), late maturation (50% at 11 years), slow growth, and episodic recruitment that is dependent on ocean conditions, accessibility and vulnerability to commercial, recreational and Aboriginal fisheries, and the 50 to 75% decline in some survey indices since the mid-1980’s.
This document provides background information and a coastwide stock assessment of Quillback Rockfish intended to support a Recovery Potential Assessment and Government decision making in 2011. Although COSEWIC recognizes only one coastwide designatable unit for Quillback Rockfish, this assessment is divided into two management units: inside and outside. Stock status is determined relative to fishery reference points consistent with DFO’s decision making framework that incorporates the Precautionary Approach.
A Bayesian state space surplus production model is employed which requires a time series of annual catch biomass from each of the fisheries, abundance indices (CPUE) from research surveys, estimated parameters including carry capacity, intrinsic rate of population growth, biomass in the first year of the model, and catchability for each CPUE series. A Reference Case model is used for management advice and sensitivity analyses are performed to assess the influence of various inputs into the model on the stock outcomes. The model is then projected over three generations into the future to develop decision tables which are presented as probabilities for four stock status indicators given various fixed total fishing mortality harvest policies.
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