Terms of Reference

Arrowtooth Flounder (Atheresthes stomias) Stock Assessment for British Columbia in 2021

Regional Peer Review – Pacific Region

October 19-20, 2022
Virtual Meeting

Chairperson: Shannon Obradovich

Context

Arrowtooth Flounder (Atheresthes stomias) is a significant species within the groundfish trawl fishery. Arrowtooth Flounder are also a minor component of the groundfish hook and line fisheries. The last stock assessment of Arrowtooth Flounder was conducted in 2015 (Grandin and Forrest 2017) with an age-structured assessment model. Since 2006, the fishery has been subject to coastwide Total Allowable Catches (TACs) of 15,000 – 18,000 mt for the Groundfish Trawl fishery with a reduction to 5,000 mt in 2020 and a closure of key fishing grounds. This reduction in TAC was in response to a declining trend in the Hecate Strait and West Coast Vancouver Island Synoptic bottom trawl surveys since the last assessment. The survey index declines also triggered the need for a new assessment.

Updated stock status and harvest advice would assist in determining whether current harvest levels are sustainable and compliant with the Sustainable Fisheries Framework (SFF). The SFF policy, A Fishery Decision-making Framework Incorporating the Precautionary Approach (PA Framework; DFO 2009), outlines the methods for applying the Precautionary Approach (PA) in the management of Canadian fisheries. Application of the PA usually implies estimation of fishery reference points and evaluation of current stock status relative to those reference points. Estimation of these quantities requires development of quantitative models conditioned on available fishery, survey, and biological data.

Since 1996, 100% observer coverage in the commercial groundfish trawl fishery has provided reliable reporting of catch and discards for the largest source of fishery mortality. Prior to 1996, however, landings of Arrowtooth Flounder were unreliable and characterised by high proportions of discards due to low market demand, low value, and the known rapid deterioration of product due to the presence of the same parasites prevalent in Pacific Hake (Merluccius productus). In many cases, the entire Arrowtooth Flounder catch in a trawl tow would be discarded, and the discards not properly recorded in fishing logbooks. As a result of this inconsistent record keeping, trends in catch statistics prior to 1996 are unreliable and it is impossible to reconstruct historical catches prior to 1996. A model-based approach to the assessment of stock status, conditioned on estimates of historical catches before 1996 is therefore unlikely to be successful and has been dropped as a possible approach to the stock assessment of this species. An alternative approach, which initiates the model from a non-equilibrium starting point and which is based on reliable catch and discard time series beginning in 1996, will be used, as was used in the 2015 assessment.

Fisheries and Oceans Canada (DFO) Fisheries Management Branch has requested DFO Science Branch provide advice regarding the coastwide assessment of this stock 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.

The assessment, and advice arising from this Canadian Science Advisory Secretariat (CSAS) Regional Peer Review (RPR), will be used to inform fisheries managers on stock status and to provide harvest management advice.

Objectives

Guided by the DFO Sustainable Fisheries Framework, meeting participants will review the following working paper to provide the basis for discussion and advice on the specific objectives outlined below.

Grandin, C., and Anderson, S.C. Assessment of Arrowtooth Flounder (Atheresthes stomias) for British Columbia in 2021. CSAP Working Paper 2019GRF03

The specific objectives of this review 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. These reference points will include the reference removal rate (FMSY), the limit reference point (LRP) and the upper stock reference (USR).
2. Assess the current status of coastwide Arrowtooth Flounder in BC waters relative to the reference points.
3. Using probabilistic decision tables, evaluate the consequences of a range of harvest policies on projected biomass relative to the reference points.
4. Describe sources of uncertainty related to the model (e.g., model parameter estimates, assumptions regarding catch, productivity, carrying capacity, and population status).
5. Provide information on environmental conditions that may impact the stock, including climate change impacts if possible.
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.

Expected Publications

• Science Advisory Report
• Proceedings
• Research Document

Expected Participation

• Fisheries and Oceans Canada (Science and Fisheries Management sectors)
• Province of British Columbia
• Indigenous communities/organizations
• Fishing Industry
• Environmental Non-Government Organizations

References

• DFO. 2009. A Fishery Decision-making Framework Incorporating the Precautionary Approach.
• DFO. 2016 Guidelines for providing interim-year updates and science advice for multi-year assessments. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2016/020: 10 p.
• Grandin, C., Forrest, R. 2017. Arrowtooth Flounder (Atheresthes stomias) Stock Assessment for the West Coast of British Columbia. DFO Can. Sci. Advis. Sec. Res. Doc. 2017/025. v + 87 p.