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(All data files are in Microsoft Excel (.xls) spreadsheet
format)
To download Puget Sound chum
salmon data base tables click on the links below:
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.
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.
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. |
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