Puget Sound Chum Salmon
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Chum salmon
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Summer Chum Salmon Conservation Initiative (SCSCI) Report Series
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Information and Data Bases
(All data files are in Microsoft Excel (.xls) spreadsheet format)

To download Puget Sound chum salmon data base tables click on the links below:

Overall Puget Sound Chum Salmon

Summer Chum Salmon

Fall Chum Salmon

Winter Chum Salmon

Discussion

Annual chum salmon escapement and runsize tables (in retrievable spreadsheet form) are provided for Puget Sound chum salmon. The estimates include regional totals for wild and hatchery chum salmon escapements and runsizes. Wild chum salmon are those fish actually produced by naturally spawning parents, and the hatchery fish are the result of artificial enhancement or recovery programs. The various data bases span different time periods, because they reflect the years that have the most reliable escapement and harvest information.

The numbers in the tables listed above represent the returns entering Washington waters through the Strait of Juan de Fuca. The runsize category is comprised of the sum of escapements and the all-citizen and tribal net harvests of chum salmon. The numbers do not include any fish returning to Puget Sound through the northern approach of Johnstone and Georgia straits (east of Vancouver Island), and they do not include any sport harvests. The northern approach and sport caught chum are not included in management data bases because of difficulties in accurately estimating the abundance and/or the rivers of origin of the fish captured in various fisheries.

The tables of escapement and runsize are organized into four categories: overall Puget Sound, summer chum, fall chum, and winter chum. The number of chum salmon in the tables for the various run timings are assembled by major region. North Puget Sound includes the Nooksack, Samish, Skagit, Stillaguamish, and Snohomish river basins, plus the independent tributaries of the region. South Puget Sound includes the Duwamish, Puyallup, Nisqually, and South Puget Sound and east Kitsap independent tributaries. Hood Canal includes all of the river systems and independent tributaries draining into the Canal. The Strait of Juan de Fuca includes all of the river systems and independent tributaries between Hood Canal and Neah Bay. Summer and winter timed chum are not found in all of the Puget Sound regions, and there are no self-sustaining chum stocks in the Lake Washington system.

These chum salmon management data bases are subject to future revision. WDFW and the co-managing Tribes are constantly upgrading escapement and catch estimates, and are attempting to develop acceptable estimates of missing runsize components. Management data bases are reviewed by the managers each year, and past values may be changed if better information becomes available. Users of these data bases should periodically check for changes.

The following is a brief summary of the approaches used to estimate Puget Sound chum salmon escapements and runsizes.

Escapement Estimates

Annual estimates of the chum spawning escapements to Puget Sound streams are developed on the watershed scale by WDFW and the Puget Sound Treaty Tribes. Natural spawning chum escapement estimates in the Puget Sound region are typically based on analysis of live chum counts collected within each watershed. Hatchery escapement estimates result from counts of the fish returning to individual artificial production sites.

Established stream sections (referred to as "index" reaches) are surveyed each year on a regular (7-10 day) schedule throughout the spawning period, environmental and staff availability issues permitting. The index surveys are conducted by teams of trained individuals that travel by foot or boat. During the surveys the observers count the number of live and dead chum (and any other salmon) present. The river miles surveyed for each index are generally fixed, but may be adjusted from survey to survey to account for unusual environmental or fish distribution conditions. "Supplemental" surveys are conducted once or twice a season on some of stream reaches not covered by the index surveys, usually focusing on the peak spawning period.

At the end of each spawning season an escapement estimate is derived for each watershed. A variety of estimation methods are used, specific to the quantity and quality of survey data collected in each watershed and stream reach. The most common analytic approach for data collected in index reaches is the "Area-Under- the-Curve" (AUC) escapement estimation method. With the AUC method the live chum observations collected through the season in each index are plotted on a graph, and a line is fit by eye through the counts. The area described under the curve is calculated (fish x days), and this value is divided by the assumed average residence time of the fish on the spawning grounds (usually 10 days) to derive an estimate of total spawner abundance in the surveyed reach. In other cases weir or fishway data, spawning redd counts, mathematical expansion factors, or other data are used for deriving escapement estimates for individual stream reaches or watersheds.

In the larger river basins entering eastern Puget Sound, chum spawning is spread throughout dozens or even hundreds of miles of stream habitat. In these cases, only a limited portion of the watershed is regularly surveyed, and expansion values derived from past baseline tagging studies are used to estimate basin-wide chum spawning activity based on the numbers of fish observed in established index reaches.

Runsize Estimates

To determine the total numbers of salmon returning to specific production areas, fish that are harvested in mixed stock and terminal fisheries must be allocated to the watersheds from which they originated. This allocation is done through a post-season process called "run re-construction," which splits the harvests in each catch area into the numbers of fish that were likely contributed by the individual stocks or management unit thought to be transiting the area. All estimated harvests for each stock or management unit are added to the escapement for that grouping to derive the estimated total return for each year.