The Pacific Salmon Commission has designated the Salmon River hatchery stock of fall Chinook as an Exploitation Rate Indicator Stock (ERIS) for all 16 naturally produced stocks of fall Chinook on Oregon's north coast. The Pacific Salmon Treaty (PST) specifies the necessity of these stocks to model the effects of mixed stock fisheries on wild Chinook salmon. The ocean migration patterns and catch rates of this stock are thought to closely resemble Oregon's north migrating Chinook from coastal basins ranging from the Necanicum River in the north to the Siuslaw River in the south. A relatively long and continuous history of mark and recapture experiments with corresponding extensive spawning ground surveys and harvest estimates from a fresh water creel, serves as the foundation for a predictive model of spawner abundance. Peak counts from two spawning ground surveys were identified as an index that strongly correlates with relatively precise abundance estimates derived from a Peterson two event mark-recapture model. Index surveys are less labor intensive than previous mark-recapture activities, and evidence suggests they are an efficient and cost effective method to estimate spawner abundance.

An age-structured state-space spawner–recruit model was fit to estimates of relative and absolute abundance, harvest, and age composition for Copper River Chinook salmon (Oncorhynchus tshawytscha) from 1980 to 2016. Bayesian statistical methods were employed to assess uncertainty in the presence of measurement error, serial correlation, and missing data. Ricker stock-recruit parameters and management reference points were estimated, including the escapement that provides for maximum sustained yield (SMSY). It is recommended that a sustainable escapement goal range of 18,500 to 33,000 fish be adopted for Copper River Chinook salmon. Escapement is evaluated by subtracting estimates of inriver harvest from estimates of inriver abundance. Escapements within this range have a high probability of producing sustainable yields.

In 2020-2024, Chinook salmon (Oncorhynchus tshawytscha) will be enumerated at 2 Anchor River sites from mid-May through early August to monitor escapement for the drainage. The south fork site, located at approximately river kilometer (RKM) 4.0, will be monitored by an Adaptive Resolution Imaging Sonar (ARIS) during high flow periods, and a resistance board weir fitted with underwater video will be used thereafter. The north fork site, located at about RKM 5.3, will be monitored by a resistance board weir with underwater video from the beginning of the Chinook salmon run in early May. Motion-detection technology will be used at each weir to record fish passage 24 hours per day. Weekly beach seine surveys will be used to capture Chinook salmon for age-sex-length (ASL) samples downstream of the confluence of the south and north forks. Chinook salmon data will be used to update estimates of the spawner-recruit relationship and harvest rate, and to provide inseason run information to managers. Coho salmon and steelhead will also be monitored in the fall of each year using the resistance board weir and video system on each fork. Coho salmon age, sex, and length will be collected via beach seining. Coho salmon escapement and harvest rate will be estimated along with an index of steelhead abundance and catch rate.

The primary goals of this study are to estimate a) the number of Chinook salmon Oncorhynchus tshawytscha smolt (=50 mm FL) leaving the Stikine River yearly from 2022 to 2024, and b) the mean length and weight of Chinook salmon smolt leaving the Stikine River annually. Additional objectives include estimating the marine harvest and marine survival of adult Chinook salmon returning to the Stikine River from the 2020–2022 brood years and estimating the length and weight of coho salmon Oncorhynchus kisutch smolt that are captured during their outmigration. A modified Petersen 2-event mark–recapture project will be conducted to estimate smolt abundance, and a coded wire tag (CWT) project relying on harvest sampling programs will be conducted to estimate harvest. Length and weight data will be collected during the CWT and event 1 smolt tagging project. Chinook salmon smolt will be marked with adipose fin clips and CWTs each spring. Marked fish will be recaptured through creel, port, and escapement sampling procedures. The Stikine River is 1 of 12 statewide Chinook salmon indicator stocks monitored by the Alaska Department of Fish and Game (ADF&G) and is both an escapement and exploitation indicator stock for the Pacific Salmon Commission (Chinook Research Team 2013, CTC 2021). ADF&G and Fisheries and Oceans Canada (DFO) use these data, along with adult escapement information (described in a separate operational plan), to make terminal and regional management decisions, and the PSC uses these data for coastwide management and stock assessment through the Transboundary and Chinook Technical Committees.