Terms of Reference

An Evaluation of West Coast Vancouver Island Chinook Salmon Visual Spawning Escapement Estimation Methods

Regional Peer Review - Pacific Region

July 8, 2014
Nanaimo, BC

Chairperson: Lesley MacDougall

Context

As part of the implementation of the Chinook Salmon Annex of the Pacific Salmon Treaty (PST), Canada is required to assess the escapement of West Coast Vancouver Island (WCVI) PST Chinook Salmon index stocks relative to escapement goals annually. Domestically, assessments of individual stocks are required to implement Canada’s Wild Salmon Policy, and meet other domestic management needs, such as managing and evaluating terminal fisheries in the WCVI area.

Given the geomorphology, remoteness and available resources, it is has not been feasible to conduct either mark recapture studies or fence counts on WCVI Chinook Salmon systems, as are done other Chinook Salmon systems that fall under the terms of the Chinook Salmon Annex of the PST. Instead, periodic visual surveys are conducted and these observations have been used with an Area Under the Curve (AUC) estimation procedures to produce an estimate of escapement for WCVI Chinook Salmon index stock. Concern has been raised by the Chinook Technical Committee of the PST that this method may have unacceptable bias and does not adequately estimate uncertainty. To address these concerns, an investigation into an alternate analytical method had been developed and studies, funded under PST Sentinel Stocks Program, have been conducted.

The objective of this review is to evaluate the alternate visual survey escapement estimation methodology and consider information gained from the independent studies and simulation modelling to provide advice respecting the applicability of the new approach for escapement estimation of WCVI Chinook Salmon index stocks. Advice arising from this Canadian Science Advisory Secretariat (CSAS) Regional Peer Review Process will be provided to DFO Fisheries Management, the Pacific Salmon Commission and the Chinook Technical Committee (CTC) established under the Pacific Salmon Treaty.

Objectives

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

Labelle, M. and McHugh, D. An Investigation of West Coast Vancouver Island Chinook Salmon Visual Spawning Escapement Estimation Methods. CSAP Working Paper 2014-15/SAL01.

1. Evaluate the Maximum Likelihood (ML) model developed to estimate spawning abundance of WCVI Chinook Salmon in index streams using periodic visual survey data, including:
1. Quantification of uncertainty of the abundance estimates; and,
2. Identifying sources of bias in the survey and estimation method.
2. Compare performance of the ML approach to the previously used AUC approach and in relation to information gained through the independent studies with respect to accuracy. 

Expected publications

• CSAS Research Document
• CSAS Proceedings

Participation

• DFO Science Branch
• Members of the Pacific Salmon Treaty, Chinook Technical Committee (PST) and Sentinel Stock Committee (PST)
• Representatives from the Alaska Department of Fish and Game, Oregon Department of Fish and Wildlife, the Washington Department of Fish and Wildlife, and the National Oceanic and Atmospheric Administration
• Representatives from the Nuu-chah-nulth Tribal Council
• Academia and Non-Government Experts

References

DFO. 2014. Proceedings of the Regional Peer Review on the West Coast Vancouver Island Chinook Salmon Escapement Estimation and Stock Aggregation Procedures. DFO Can. Sci. Advis. Sec. Proceed. Ser. 2014/025 In press.

DFO. 2014.  West Coast Vancouver Island Chinook Salmon Escapement Estimation and Stock Aggregation Procedures. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2014/038. In press.