Science Advisory Report  2011/084

Stock Assessment for the inside population of Yelloweye Rockfish (Sebastes ruberrimus) In British Columbia, Canada for 2010

Summary

• In 2008, COSEWIC recognized two designatable units (DUs), or populations, of Yelloweye Rockfish in British Columbia (B.C.); inside and outside and both these DUs were designated as special concern.
• This document provides a summary of the stock status and projections for the inside population of Yelloweye Rockfish in B.C.  Stock status and projections are presented relative to reference points consistent with DFO’s decision making framework policy which incorporates the Precautionary Approach.
• Yelloweye Rockfish range throughout B.C. and are observed at depths from 20 to 250 metres. They are demersal and exist over hard, complex substrates such as rock reefs and boulder fields.
• In 2009, an estimated 15.2 t of Yelloweye Rockfish were caught in fisheries throughout the inside management unit; 2.8 t from Aboriginal fisheries, 8.1 t from commercial groundfish fisheries and 4.3 t from recreational fisheries.
• A Bayesian surplus production (BSP) model is used to assess the inside population of Yelloweye Rockfish in B.C. This model employs catch data derived from historic catch records reconstructed back to 1918, life history data to estimate the intrinsic rate of increase (r), and abundance trends from commercial hook and line catch records and two longline research surveys.
• The BSP model provides a fairly good fit to the stock trend data and shows a stock decline in the 1980s and 1990s during high fishery catches. The BSP model accounts for the continued decline in abundance since the 1990s, during a time of lowered catches, by updating the prior for r, to give a posterior mean for r considerably less than the prior mean.
• Sensitivity analyses were conducted to evaluate the sensitivity of model results to a wide variety of alternative input and model settings.
• Stock status for the inside population of Yelloweye Rockfish is evaluated using a reference case BSP model run. This model run estimates that the stock biomass in 2009 is at 780 tonnes (coefficient of variation [CV] 0.46), which is 12% (CV 0.43) of the initial biomass of 6466 t (CV 0.40) in 1918.
• There is a 5% probability that the inside Yelloweye Rockfish population in 2009 is greater than the fisheries Limit Reference Point (LRP), consistent with Fisheries and Oceans Canada’s (DFO’s) fishery decision-making framework incorporating the Precautionary Approach. The population,is likely within the Critical Zone.
• Replacement yield in 2009 (RepY₂₀₀₉) is estimated at 19 t (CV 0.49) with catches of 15 t in 2009 estimated at 78% (CV 0.66) of replacement yield. Fishing mortality in 2009 (F₂₀₀₉) is estimated to be 1.38 (CV 0.70) that of the fishing mortality at MSY (F_MSY).
• Stock projections show that the stock will increase over time. The probability that the current biomass in 2009 (B₂₀₀₉) >0.4 B_MSY at the end of a 5 year horizon is low (< 14%) for all harvest policies. Given a fixed catch (total fishing mortality) harvest policy of 15 t, this probability increases to about 44% at the end of a 40 year time horizon and 56% at the end of an 80 year time horizon.
• An exploratory methodological analysis that extends the BSP model to incorporate pinniped predation on a fish stock is presented for illustrative purposes only.

This Science Advisory Report is from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, regional advisory meeting of April 7-8, 2011 on the Stock assessment and harvest advice for Pacific Lingcod in outside waters and for Strait of Georgia Yelloweye Rockfish. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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