Terms of Reference

Quantitative Stock Assessment and initial limit reference points for Dolly Varden (Salvelinus malma) from the Rat River, NWT, 2022

Regional Peer Review – Ontario and Prairie Region

January 25-26, 2024

Winnipeg, MB and Virtual Option

Co-chairs: Margaret Treble, Robert Charlie

Context

Among harvested stocks of anadromous Dolly Varden (Salvelinus malma), the Rat River receives considerable attention given it supports inland subsistence fisheries for beneficiaries in two Indigenous land claim areas (Gwich’in Settlement Area and Inuvialuit Settlement Region). There is a long history (>25 years) of collaborative fisheries data collection between Indigenous co-management partners and Fisheries and Oceans Canada (DFO) that are used to monitor the stock, which includes harvest, biological, catch-effort, and tagging data. The last assessment for the Rat River took place in February 2015 and assessed data from 2009-2014 (DFO 2017). Based on the available information at the time, the population appeared to be stable and sustainably harvested.

However, population declines have been observed in several key Dolly Varden stocks in recent (last 3-4 years) and historical (>50 years ago) time frames. Increasing concerns are being raised by fishers, Hunters and Trappers Committees (HTCs), Renewable Resource Councils (RRCs), and regional co-management boards. Of particular concern is that the proximate and ultimate reason(s) for the decline in these stocks are not understood, including how environmental conditions can affect the stock and the various subsistence fisheries.

Discussions about how to improve harvest decision-making for Dolly Varden have been ongoing among DFO Fisheries Management (DFO FM), the Gwich’in Renewable Resources Board (GRRB), the Fisheries Joint Management Committee (FJMC), and Parks Canada Agency, all of whom are signatories to the Dolly Varden Integrated Fisheries Management Plan (IFMP). The IFMP underscores the intent to follow principles of the precautionary approach – but DFO has not yet established the Limit Reference Points (LRPs) needed to delineate stock status zones consistent with the precautionary approach framework under Bill C-68. Population models can incorporate the time-series of standardized fisheries-dependent data to evaluate the effects of harvest and determine current stock status. Furthermore, these models can be used to develop LRPs that can help inform co-management decision-making.

A key outcome of the current stock assessment will be the generation of an initial LRP for the Rat River population. This will create a basis for future work to evaluate different scenarios of LRPs and harvest control rules that can also be used for other Dolly Varden populations in the NWT (e.g., Big Fish River). Ultimately, the LRPs, harvest control rules, and harvest goals will be reviewed and refined to incorporate other data sources, separate from this peer-review to include Indigenous Knowledge, via a community-based peer-review process that includes co-management partners.

Objectives

Fisheries Management requests DFO Science advice on sustainable harvest levels for anadromous Dolly Varden from the Rat River population; specifically:

1. Update and summarize the harvest data to include 2015-2022 data;
2. Present results of genetic mixed-stock analyses of the contribution of Rat River Dolly Varden to coastal fisheries (2015-2022);
3. Summarize results and trends of fisheries-dependent (biological and catch effort based on harvest monitoring) and –independent (biological based on tagged fish) data collected between 2015 and 2022;
4. Evaluate population estimates based on mark-recapture analyses of tagging data (2015-2022);
5. Employ population models using entire timeseries (1995-2022) of fisheries-dependent data to determine stock status;
6. Evaluate effects of environmental conditions on catch-effort; and
7. Evaluate candidate reference points (Limit, Upper Stock Reference).

Expected Publications

• Science Advisory Report
• Research Document

Expected Participation

• Fisheries and Oceans Canada (DFO) (Ecosystems and Oceans Science, Species at Risk, and Fisheries Management sectors)
• Academics
• Gwich’in Renewable Resources Board
• Fisheries Joint Management Committee
• Local Community Harvesters
• Other invited experts

References

• DFO. 2017. Assessment of Dolly Varden from the Rat River, Northwest Territories 2009–2014. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2016/058.