Terms of Reference
Status Update of Pacific Cod (Gadus macrocephalus) for West Coast Vancouver Island in 2023
Regional Peer Review - Pacific Region
October 20, 2023
Chairperson: Steven Schut
Pacific Cod (Gadus macrocephalus) is a commercially important species of cod that occurs along the entire coast of British Columbia (BC), Canada. It is considered to be a short-lived species (10-13 years). The majority of catches are taken in Hecate Strait and Queen Charlotte Sound, where abundance is highest, although large catches have historically been taken off the West Coast of Vancouver Island (WCVI). Pacific Cod are caught by the groundfish trawl fishery and occasionally by hook and line fisheries. Four stocks of Pacific Cod are defined for management purposes in BC: Strait of Georgia (4B); West Coast Vancouver Island (3CD); Queen Charlotte Sound (5AB); and Hecate Strait (5CD). This science request is for Area 3CD (WCVI) only.
The 2020 stock assessment for Pacific Cod (Gadus macrocephalus), forecast the Area 3CD stock to be in the Cautious zone with 97-98% probability over the range of catch scenarios considered (DFO 2021). This followed a notable reduction in the 2018 WCVI survey index (approximately 26-27% of the 2014 and 2016 observations). Although this stock has not been prescribed as a major stock under the Fish Stock Provisions of the Fisheries Act, the Precautionary Approach (PA) recommends that management measures “encourage stock growth and arrest preventable declines, and the development of a rebuilding plan should be initiated sufficiently in advance to ensure that the plan is ready to be implemented if a stock declines to its LRP” (DFO 2009).
Due to the COVID-19 pandemic, the scheduled 2020 WCVI synoptic bottom trawl survey was postponed to 2021, then returned to its regular biennial schedule in 2022. Both the 2021 and 2022 index points were of a similar low magnitude to the 2018 observation. Catches from 2018-2020 were also lower than in previous years. The commercial catch per unit effort (CPUE) index decreased substantially in 2018 but has increased slightly since then, with increases in commercial catch. Given the low index point in 2018, Fisheries and Oceans Canada (DFO) Science recommended updating the assessment when new survey information became available (DFO 2021).
The current delay-difference model used for the assessment relies on an index of annual mean weight in the commercial fishery, which is derived from commercial length samples collected at sea. Since 2014, there has been a notable decline in commercial sampling effort for Pacific Cod, with commercial sampling ceasing altogether in 2020 following the COVID-19 pandemic and changes to the at-sea observer program. The Pacific Cod Technical Working Group (TWG) met in 2022 and again in 2023 and evaluated a generalized linear model (GLM) for predicting the commercial mean weight index in missing years from a mean weight index derived from survey samples. The TWG found that the GLM provided a reasonable prediction of the commercial annual mean weight index for Area 3CD.
Fisheries and Oceans Canada (DFO) Science requested an update to the stock status of the 3CD Pacific Cod stock using a procedure to fill in recent missing years in the commercial mean weight index. The assessment and advice arising from this Canadian Science Advisory Secretariat (CSAS) Science Response (SR) process will be used to inform the Pacific Cod stock assessment models, as well as to inform fisheries management of the current stock status. No additional fisheries management or catch advice will be presented in this SR process.
The specific objectives of this review are to:
- Present a generalized linear model (GLM) to predict the Pacific Cod commercial annual mean weight index from the WCVI survey index, which was developed with input from the TWG in 2022 and 2023.
- Calculate the model-averaged stock status of WCVI Pacific Cod at the beginning of 2023 and the projected stock status in 2024 under a no-fishing scenario.
- Examine and identify uncertainties in the data and methods.
- Recommend future work on potential causes of decline of the Area 3CD stock, and on investigation of alternative approaches for providing catch advice for this stock in the continuing absence of commercial biological samples.
- Science Response
- Fisheries and Oceans Canada (DFO) (Ecosystems and Oceans Science)
- International Pacific Halibut Commission
- DFO. 2009.A fishery decision-making framework incorporating the Precautionary Approach.
- DFO. 2021. Status update of British Columbia Pacific Cod (Gadus macrocephalus) for West Coast Vancouver Island (Area 3CD), and Hecate Strait and Queen Charlotte Sound (Area 5ABCD) in 2020. DFO Can. Sci. Advis. Sec. Sci. Resp. 2021/002.
Participation to CSAS peer review meetings is by invitation only.
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