Tag Archives: stock assessment

Chinook Salmon Escapement Estimation to the Skeena River Using Genetic Techniques

The Skeena River is host to the second largest aggregate of Chinook salmon in British Columbia. While the aggregate is a PSC escapement indicator stock, there are no biologically based escapement goals for this population. This project produces an annual escapement estimate for the Skeena River Chinook aggregate and provides information on the stock components that make up the Chinook return to the Skeena River. The project consists of genetic analyses of samples from Chinook salmon caught at the Tyee Test fishery in 2021. The project uses samples and data from two independent programs, the Tyee Test Fishery and the Kitsumkalum mark-recapture program. Chinook salmon scale samples will be collected from the Tyee Test Fishery and the DNA from the samples will be compared against genetic baselines from Skeena Chinook salmon populations. The proportion identified as Kitsumkalum Chinook will be expanded to generate escapement estimates for the Skeena River aggregate using the mark-recapture estimate of escapement for the Kitsumkalum population.

 

 

Mixed Stock Analysis of U.S. Districts 101, 102, and 103 Sockeye Seine Fisheries

Annual stock-specific run reconstructions (catch plus escapements) are required to accurately estimate relative contribution of each stock caught in Northern Boundary Area fisheries. Estimates of national origin of contributing stocks provides the most reliable information currently available to complete these run reconstructions, and are used to evaluate stock-specific productivity and revise pre-season forecasts. While the catch of Nass and Skeena sockeye salmon is only subject to treaty harvest-sharing annexes in the Alaska District 101 gillnet and Alaska District 104 purse seine fisheries, the harvest of these stocks in all fisheries, and their escapements, needs to be estimated in order to calculate the total run and the percentage caught in the annexed fisheries.
This project will complete genetic stock identification (GSI) analysis on sockeye salmon tissue samples collected from the 2016 commercial purse seine fisheries in Districts 101, 102, and 103 in Southeast Alaska. This project is a complement to the ongoing project at the Auke Bay Laboratory for Northern Boundary Area sockeye salmon GSI in Districts 101 and 104, and continuing work by DFO in Areas 3, 4, and 5; and will allow for complete assessment of the catches of Nass and Skeena sockeye salmon in all major Northern Boundary Area fisheries for run reconstructions. Estimates will be provided for up to 3 time strata in District 101, up to 3 time strata in District 102, and over the entire season in District 103, for a total of 1,500 samples analyzed.

Boundary Area Coho Escapement

The Hugh Smith Lake coho salmon population is substantially exploited by mixed-stock fisheries in both the U.S. and Canada and is, therefore, a key indicator stock used to monitor total adult abundance and escapements, and the pattern and intensity of exploitation by these fisheries on populations in the northern boundary area. It is the only system in the southern portion of Southeast Alaska where a total count (with back-up mark-recapture estimate) of coho salmon escapement has been routinely collected since 1982. Its location 70 km southeast of Ketchikan makes it a particularly strategic indicator stock for boundary area fisheries. It has also been one of three key indicator stocks used to measure the overall abundance of wild coho salmon available to the Alaska troll fishery and to measure the exploitation rate by the fishery.
Escapement projections are made from both the cumulative weir count and estimation models based on recovery of coded-wire tags to provide real-time information for management of fisheries for escapement. Peak helicopter survey counts at other Boundary Area streams provide an index with greater coverage that complements higher resolution assessment at Hugh Smith Lake.

 

Hugh Smith Lake Coho Smolt Enumeration and Marking

The Hugh Smith Lake coho salmon population is substantially exploited by mixed-stock fisheries in both the U.S. and Canada and is, therefore, a key indicator stock used to monitor total adult abundance and escapements, and the pattern and intensity of exploitation by these fisheries on populations in the northern Boundary Area. Its location 70 km southeast of Ketchikan makes it a particularly strategic indicator stock for boundary area fisheries. It has also been one of three key coded-wire tagged indicator stocks used to measure the exploitation rate by the Alaska troll fishery and to estimate the overall abundance of wild coho salmon available to the fishery. Timely escapement projections are made from both the cumulative weir count and estimation models based on recovery of coded-wire tags to provide real-time information for management of fisheries for escapement goals.
The Hugh Smith Lake coho salmon population has been the only long-term, continuously operated wild coho indicator stock project in the northern boundary area, with a record of catch, escapement, smolt production, marine survival, and age composition estimates dating from 1982. The proposal would continue to fund operation of a smolt weir to enumerate and coded-wire tag coho salmon smolts emigrating from Hugh Smith Lake to generate total population estimates, including total smolt production, marine survival, exploitation rate, and catch by area, time, and gear type. Coho smolt estimates and tag recovery rates in the Southeast Alaska troll fishery will be used to generate inseason estimates of marine survival and total adult abundance for fishery management. Estimates of brood year smolt production and adult return by age class will be used to evaluate and refine the biological escapement goal. Counts and samples of sockeye salmon smolts are also obtained at the smolt weir and have been used to evaluate escapement goals and effectiveness of sockeye salmon stock enhancement efforts. The proposed project will continue a core stock assessment program needed to manage fisheries for coho salmon in the northern Boundary Area.

Terminal Abundance of WCVI Chinook Salmon

Chinook salmon stocks originating from the West Coast of Vancouver Island (WCVI) contribute significantly to the ocean harvests in fisheries in Southeast Alaska and northern British Columbia, as well as being of prime importance to near-shore fisheries along the WCVI itself. Consequently, commercial and sport fishermen, as well as First Nations up and down the coast have a vested interest in the status of WCVI Chinook salmon. Management agencies and organizations responsible for fisheries in Southeast Alaska, northern British Columbia, and along the WCVI have need of stock status information concerning WCVI Chinook salmon.
The overall goal of this project is to estimate the aggregate terminal returns of WCVI hatchery and natural origin Chinook salmon, including catch plus escapement inside the surf line such that the estimates are asymptotically accurate and have a CV of 15% or less. This will be achieved through 1) the first comprehensive assessment of catch plus escapement along the WCVI, and 2) refinement of the ‘driver stock’ approach for estimating aggregate terminal return from a distant fishery.
The “driver stock” approach was first developed through the Sentinel Stock Program, and is based on the assumption that an indicator stock (or stock group) experiences the same exploitation and maturation rates as the aggregate. If the assumption holds, the incidence of this indicator stock group in an ocean fishery (using information such as CWT, otolith, DNA) and in its terminal area would have the same ratio as the catch of the indicator stock group in the same ocean fishery to its terminal run size. When using a single CWT stock, estimating terminal run size is simple. However, given the complexity of the WCVI stock aggregate and terminal WCVI fisheries, the key assumptions of the method – i.e. that maturation rates and exploitation rates are constant across the WCVI aggregate, were not met.
The purpose of this project is to 1) improve the precision of the terminal return estimates of natural and hatchery origin chinook salmon along the WCVI, 2) quantify the variation in maturation, exploitation rates, abundance across the WCVI aggregate, and 3) use the additional information to refine the application of the driver stock approach to the WCVI aggregate through development of a Bayes method. These results will benefit existing stock reconstructions and forecasts in the assessment of the WCVI Chinook salmon stock complex.