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Pacific Ocean Perch (Sebastes alutus) stock assessment for British Columbia in 2023

Regional Peer Review - Pacific Region

Nov 6 - Nov 7, 2023
 Virtual Meeting

Chairperson: Ben Davis

Context

Pacific Ocean Perch (POP, Sebastes alutus) is a commercially important species of rockfish that inhabits the marine canyons along the coast of British Columbia (BC). Among the current annual Total Allowable Catch (TAC) of rockfish on the west coast of Canada, POP has the second largest single-species quota after Yellowtail Rockfish (S. flavidus). The status of POP in BC has been assessed previously as three separate stocks: Queen Charlotte Sound (QCS, Pacific Marine Fisheries Commission [PMFC] major areas 5ABC) in 2017, west coast Vancouver Island (WCVI, PMFC areas 3CD) in 2012, and west coast Haida Gwaii (WCHG, PMFC areas 5DE) in 2012. All three previous POP stock assessments (Haigh et al. 2018; Edwards et al. 2013a, b) showed a decline from a non-fished equilibrium. Stock status in all areas was considered to be ‘Healthy’ based on Precautionary Approach (PA) criteria: 5ABC B2017/BMSY = 1.03 (0.54, 1.97), 3CD B2013/BMSY = 1.53 (0.55, 3.32), and 5DE B2013/BMSY = 1.61 (0.57, 3.57)Footnote 1.

This stock assessment proposes to model all three stocks as regions by assuming an annual coastwide recruitment event that is allocated among the regions based on model fits to the stock information for each area. Although this technique has rarely been tried in BC, other jurisdictions have employed this approach of recruitment allocation by area, e.g., Yelloweye Rockfish in coastal waters off three states (Washington, Oregon, and California) using the Stock Synthesis model platform by the National Oceanic and Atmospheric Administration (NOAA) (Taylor and Wetzel 2011; Gertseva and Cope 2017). This stock assessment will also fit models to each area separately to compare the results with the coastwide model.

The QCS stock is the largest of the three in BC and has traditionally had substantial fishing pressure, especially during the years of targeting by foreign fleets (1965-1976). This early fishery was sustained by a strong recruitment event that occurred in the early 1950s. The depletion of the QCS stock halted briefly after the 1977 introduction of the 200 nautical mile limit, before resuming with the development of a domestic bottom trawl fleet that continued to target this species. The domestic fishery was sustained by a few strong year classes that recruited in the late 1970s and early 1980s. The declining trend appeared to end in 2006, coincident with a 700 t reduction in the TAC. After a 2010 stock assessment (Edwards et al. 2011), Fisheries and Oceans Canada (DFO) management implemented a further TAC reduction in 5AB/5CD of 258 t per year over a three year period (an additional 774 t total reduction) as a conservation measure. This management improved the 2017 stock status relative to that in 2011 (Haigh et al. 2018).

Fisheries and Oceans Canada (DFO) Fisheries Management has requested that DFO Science Branch provide advice regarding the assessment of the three POP stocks relative to reference points that are consistent with the DFO’s Fishery Decision-Making Framework Incorporating the Precautionary Approach (DFO 2009), including the implications of various harvest strategies on expected stock status. In 2019, Bill C-68 was enacted to amend the Fisheries Act (now ss. 6.1-6.3) with the Fish Stocks Provisions (FSP). The FSP came into force through amendments to the Fishery (General) Regulations (FGR) on April 4, 2022.The FSP established binding obligations on the Minister of Fisheries and Oceans to (1) maintain major fish stocks at levels necessary to promote sustainability (s. 6.1); and (2) develop and implement rebuilding plans for stocks that have declined to or below their limit reference point (s. 6.2). An initial list of 30 major stocks (for all of Canada) was identified (Batch 1) out of 62 proposed major stocks. The three POP stocks appeared on the second list and may be included in Batch 2.

The advice arising from this Canadian Science Advisory Secretariat (CSAS) Regional Peer Review (RPR) will be used to inform fisheries management decisions to establish catch levels for the species. This work will also inform and supplement decisions external to DFO, specifically for the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).

Objectives

The following working paper will be reviewed to provide the basis for discussion and advice on the specific objectives outlined below.

Starr, P.J., and Haigh, R. Pacific Ocean Perch (Sebastes alutus) stock assessment for British Columbia in 2023. Request ID 225.

The specific objectives of this science response are to:

  1. Recommend reference points consistent with the DFO Precautionary Approach (PA), including the biological considerations and rationale used to make such a determination. If possible, these should include the DFO limit reference point (LRP) of 0.4BMSY and the upper stock reference (USR) of 0.8BMSY recommended in the PA for each stock. The following additional reference points will be presented: BMSY, uMSY, 0.2B0, and 0.4B0 for each stock.
  2. Assess the current status of Pacific Ocean Perch in BC waters coastwide (excluding area 4B), and in the three areas (5ABC, 3CD, 5DE), relative to the selected reference points. Discuss differences observed between regional models and the coastwide combined model.
  3. Using probabilistic decision tables, evaluate the consequences of a range of harvest policies on projected biomass (and exploitation rate) relative to the reference points and provide additional stock metrics for each stock.
  4. Conditional objective (to be addressed if a stock is assessed to be in the Critical Zone): Provide guidance for a management rebuilding plan under the DFO PA framework for POP to satisfy recent legislation (Bill C-68). Provide probabilistic decision tables that demonstrate a high probability of the stock growing out of the Critical Zone (i.e., above the LRP) within a reasonable timeframe (1.5-2 generations or tmin under no fishing, DFO 2023).
  5. Describe sources of uncertainty related to the model (e.g., model parameter estimates, assumptions regarding catch, productivity, and population status).
  6. Recommend an appropriate interval between formal stock assessments, indicators used to characterize stock status in the intervening years, and/or triggers of an earlier than scheduled assessment (DFO 2016). Provide a rationale if indicators and triggers cannot be identified.
  7. Explore environmental effects, including climate change, on the stock assessment with the understanding that their incorporation at this point is preliminary.

Expected Publications

Expected Participation

References

Notice

Participation to CSAS peer review meetings is by invitation only.

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