Science Advisory Report 2011/072
Stock Assessment and Recovery Potential Assessment for Quillback Rockfish (Sebastes Maliger) along the Pacific coast of Canada
- In November 2009, Quillback Rockfish in British Columbia (B.C.) were designated as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).
- COSEWIC recognizes one coastwide Quillback Rockfish designatable unit. For this assessment, Quillback Rockfish are divided into two management units; inside (East of Vancouver Island) and outside (remainder of the coast).
- This document provides a summary of the stock status and projections as a requirement of the recovery potential assessment for Quillback Rockfish in B.C. Status and projections are presented relative to reference points consistent with DFO’s decision making framework policy which incorporates the Precautionary Approach.
- Quillback Rockfish range from the Gulf of Alaska to Southern California and are common throughout B.C. marine waters. They have been caught in commercial fisheries from approximately 14 to 143 metres in depth over rock habitats. Estimates of habitat area in B.C. for this species ranges from 27,000 to 56,000 square kilometres.
- Stock status is assessed using a Bayesian state space surplus production (BSP) model where fishing is the only source of mortality for the stock. Future stock outcomes from a reference case BSP model are used to assess the recovery potential of the Quillback Rockfish stock under various fixed total fishery mortality harvest policies.
- In 2011, median biomass (B2011) for the outside management unit is 6,480 tonnes (coefficient of variation [CV] 1.21) and for the inside management unit is 2,668 tonnes (CV 0.60).
- The median Biomass (B) at Maximum Sustainable Yield (MSY) or Bmsy is 9,307 tonnes (CV 0.60) for the outside management unit and 5,475 tonnes (CV 0.32) for the inside management unit.
- Median B2011/Bmsy for the outside management unit is 0.736 (CV 0.57) and for the inside management unit is 0.493 (CV 0.41).
- The median biomass in 2011 is 37.7% (CV 0.65) of the biomass in 1918 (B1918) for the outside management unit and 27.4% (CV 0.47) for the inside management unit.
- Generation times for the outside and inside management units for Quillback Rockfish are estimated at 32.0 and 28.5 years, respectively.
- For the outside management unit, given the reference case, a 95% probability of the population >0.4 Bmsy is expected to be achieved in 15 years at a fixed total fishery mortality of about 30 tonnes, and in 90 years at a fixed total fishery mortality of about 90 t.
- For the inside management unit, given the reference case, a 95% probability of the population >0.4 Bmsy is expected to be achieved in 90 years at a fixed total fishery mortality of approximately 25 tonnes.
- Given the reference case, a 95% probability of the population >0.8 Bmsy is expected to be achieved for the outside management unit in 90 years at a fixed total fishery mortality of about 60 tonnes, and for the inside management unit this is not expected to be achieved in 90 years with a harvest.
- In 2010, for the outside management unit, the total mortality from all fisheries is 158.6 tonnes, of which 116.5 t was taken by the commercial groundfish fishery, 41.8 t by the recreational fishery, and 0.3 t by the salmon troll fishery. For the inside management unit, the total mortality from all fisheries is 33.9 tonnes, of which 24.8 t was taken by the commercial groundfish fishery, 9.0 t by the recreational fishery, and 0.1 t by the salmon troll fishery.
- Management of a species specific Total Allowable Catch (TAC) for Quillback Rockfish in commercial and recreational fisheries may be considered and would mitigate the possibility of over harvesting this species within the current species aggregate quotas.
- In addition to the Rockfish Conservation Strategy mitigation measures already implemented, additional reductions to fishery harvests may be considered.
This Science Advisory Report has resulted from a Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, Pacific Regional Advisory Process meeting held on May 31, 2011, on Stock Assessment and Recovery Potential Assessment for Quillback Rockfish (Sebastes maliger) Along the Pacific Coast of Canada. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.
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