Terms of Reference

Migration speed, run timing, and diversion rate for Interior Fraser River Steelhead

Regional Peer Review - Pacific Region

January 31 - February 1, 2024

Vancouver, BC

Chairpersons: Geoff Lowe and Mike Bradford

Context

Interior Fraser Steelhead Trout (Chilcotin and Thompson River Designatable Units (DUs)), have recently been assessed as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC 2020), and abundance of this aggregate is at historic low levels (Bison 2022). Fisheries and Oceans Canada (DFO) requires quantitative information about the spatio-temporal distribution of these populations to limit impacts by salmon fisheries. There is significant disagreement among First Nations, stakeholders, and various government agencies about the degree to which various salmon fisheries impact Fraser River Steelhead Trout. Historic exploitation and fishery-dependent mortality patterns are scarce and incomplete due to the absence of sampling programs focused on Fraser River Steelhead Trout. Consequently, estimates of catch and exploitation rate for Fraser River Steelhead Trout for use in conventional stock-assessment procedures are not available in most Canadian salmon fisheries.

A previous model was developed to estimate the potential range of impacts of marine and freshwater fisheries on the Thompson River population of Steelhead. However, an evaluation of that model concluded that the lack of reliable empirical data and the use of many subjective and undocumented assumptions precluded validation of the majority of parameter estimates and calculations used in those models (DFO 2006).

To address this issue, DFO Fisheries Management has requested that Science Branch assess and validate information available to inform key input parameters required for the development of fishery planning models including migration speed, run timing, and diversion rate, in a transparent way. As part of this work, a new set of models to estimate historical run timing in the lower Fraser River for Interior Fraser Steelhead Trout will be co-developed by DFO Science and Fisheries Management and evaluated. These models will explicitly account for uncertainty and provide credibility intervals for the estimates. These estimates will need to be based on data for Fraser River Steelhead Trout at the aggregate level because the historic time series of catch data does not clearly differentiate the Thompson and Chilcotin populations from other Fraser River Steelhead Trout.

The assessment and advice arising from this Canadian Science Advisory Secretariat (CSAS) Regional Peer Review (RPR) will be used to develop fisheries management plans for Steelhead Trout and recovery plans for these two populations if listed under the Species at Risk Act (SARA), including the development of the fishery exposure and planning models that will be reviewed in a subsequent process.

Objectives

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

Jenewein, B., Davis, B., and Hawkshaw, M. Migration speed, run timing, and diversion rate for Interior Fraser Steelhead Trout. CSAP Working Paper. 2023. Request ID 1125.

The specific objectives of this review are to:

1. Compile information on migration speed, run timing, and diversion rate of Steelhead Trout that may provide insight where there are information gaps specifically for Fraser River Steelhead Trout.
2. Estimate historical run timing parameters (peak and duration of return) for Steelhead Trout in the lower Fraser River, based on the best available data.
3. Evaluate the models developed for (2) by examining and identifying uncertainties in the data and modelling approach. This will include using simulation analysis to provide insight as to the reliability of the model given the data quality.
4. Identify research needs to address data gaps and/or potential concerns.

Expected Publications

• Science Advisory Report
• Research Document

Expected Participation

• Fisheries and Oceans Canada (DFO) (Ecosystems and Oceans Science and Fisheries Management)
• Academia
• First Nations
• Governmental Agencies
• Industry
• Other Invited Experts

References

• Bison, R. 2022. Status update for Interior Fraser Steelhead. Memo dated July 15, 2022. Ministry of Forests, Lands, Natural Resource Operations & Rural Development.
• COSEWIC. 2020. COSEWIC assessment and status report on the Steelhead Trout Oncorhynchus mykiss (Thompson River and Chilcotin River populations) in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xvi + 104 pp.
• DFO 2006. Proceedings of the PSARC Salmon Subcommittee Meeting, October 18, 2006. DFO Can. Sci. Advis. Sec. Proceed. Ser. 2006/027.