The annual historic run size to the Columbia River was estimated to be
1,392,000 chum salmon. In 1951 the chum salmon run size on the Washington
side of the Columbia River was estimated at 25,000 adults. Since 1959,
the population has been relatively stable with the annual minimum chum
salmon run size ranging from 300 to 5,700 adults. Preliminary data from
1999 would suggest that the minimum run size is estimated to be near 3,000
adults. Current run size is less than 3% of historic run size, and is
less than 12% of the 1951 run size.
Chum Salmon were distributed from the mouth of the Columbia River to
Walla Walla River. Most of the historic distribution was confined to below
Celilo Falls, which is near River Mile 200 on the Columbia River located
just upstream of The Dalles Dam.
Current distribution is similar to the historic distribution, with annual
runs of chum salmon passing Bonneville Dam. No chum salmon have been observed
above The Dalles Dam in more than 10 years. However, before the mid 1980's
chum salmon were occasionally observed above The Dalles Dam.
Chum salmon distribution in Lower Columbia River tributaries is often
limited to the lower 1/3 of the mainstem and tributaries in this area
due to the high gradient nature of Lower Columbia River tributaries.
Male chum salmon with spawning
Female chum salmon with spawning
Historically every major and some minor tributaries to the Columbia River
had chum salmon populations. On the Washington shore, a 1951 assessment
identified thirteen self-sustaining populations with run size estimates
above 300 fish.
Currently, two population centers exist for chum salmon. The lower is
located in the Grays River area and is likely maintained by populations
using Crazy Johnson and Gorley Creeks, which are tributaries to the lower
The second population center is located below Bonneville Dam and consists
of spawners in Hamilton Creek, Hardy Creek, and the mainstem of the Columbia
near Ives Island.
Observations of chum salmon still occur in most of the thirteen basins/areas
that were identified in 1951. However, there are usually less than 10
fish observed in these areas. It is unclear if these are self-sustaining
populations or are composed of strays from other more productive areas.
If the origin of fish in these other basin are composed of primarily
strays, then the number of self-sustaining populations on the Washington
shore has decreased from thirteen to two during the last 50 years.
In 1999 WDFW located another Columbia River mainstem spawning area for
chum salmon located near the I-205 bridge.
Male chum salmon battling
for dominance on the spawning grounds
Entry of adults into freshwater at the mouth of the Columbia occurs from
October through December. Entry into Grays River peaks in November. At
Hamilton and Hardy Creeks entry is later, peaking in December.
Peak spawning time is from mid-November to early-December on Grays River.
Spawning peaks later for the Hamilton and Hardy populations and its peak
is generally in late December.
Emergence is likely to occur between February and April. Outmigration
occurs from March through May of the same year. Peak outmigration from
Hardy Creek occurs in April.
Age at maturity ranges from three to six. Most chum salmon return as
age 4 fish. Jacks (age 2) are rare.
The southern extent of chum salmon is only to the mid-Oregon Coast. Since
Columbia River chum salmon are near the lower limit of their range, they
may be less productive and more vulnerable to extinction risk.
Historic release of hatchery chum salmon have occurred within this region.
The only hatchery program currently operating in this region is the Grays
River/Chinook River program. Its purpose is to develop a local broodstock
for rebuilding chum populations near the Grays River area and to lessen
extinction risk due to catastrophic events. WDFW is finalizing a Hatchery
and Genetic Management Plan for this program that will provide more details.
Self-sustaining populations of chum salmon are primarily found in modified
habitats. Some habitats were specifically modified to increase chum salmon
production such as the Gorley Creek and Hamilton Creek spawning channels.
Habitat modification has also occurred in Hardy Creek with major channel
moving and in Ives Island area during the construction of the Bonneville
Dam Second Powerhouse. Although the intent of these projects was not to
increase chum salmon abundance, we have observed relatively high levels
of groundwater flow in the spawning gravel used by chum salmon in these
Crazy Johnson Creek, a tributary to the lower Grays River, has not been
modified to any large extent. A channel modification project to the Grays
River was completed to reduce the risk of the Grays River migrating back
into the lower portion of Crazy Johnson Creek.
All self-sustaining population chum population in the lower Columbia
have habitat conditions that favor high egg to fry survival. All spawning
areas have springs, which promote high water exchange through the redd.
The literature suggest that chum often prefer these sites. Second, these
sites are located in areas that are not at risk to bed scour. Once eggs
are deposited, it is unlikely that they will wash out. Other historical
spawning areas in the Lower Columbia River are at a high than historic
risk for bed scour and/or sedimentation.
The most concentrated development has occurred with the lower 1/3 of
Columbia River tributaries, which overlaps totally with the historic range
of chum salmon. Armoring of steam banks and lack of functional side/overflow
channels (flood plain connectivity) have increased the risk of egg scour
and eliminated side channel habitats which chum salmon have shown a preference
Since most of historic chum spawning area in the lower Columbia River
tributaries is located in alluvial reaches just below the high gradient
transport reach, sediment from upslope activities, such as logging and
road building, is deposited in these reaches. The level of fine sediment
in gravel is likely higher than historic conditions and above conditions
found in properly functioning habitat.
The Columbia River is migration corridor for chum salmon smolts. Historic
outmigration flows from the Columbia River have been estimated to be near
500,000 cfs as compared to current estimates of 300,000 cfs or less in
most years. In addition, the turbidity during the historic spring peak
was likely higher than it is today. Alteration of the migration corridor
has increased predator habitat and the predation rates since fish take
longer to migrate and are more easily observed by native and non-native
There have been major changes in the estuary habitat of the lower Columbia
River. Sherwood et al . 1990 estimated the tide flats, swamps, and wetland
in the Columbia River estuary has been reduced by 40% between 1870 and
1970. The Corps of Engineers has created Rice Island from dredge spoils,
which has been the primary breeding ground for the largest colony of Caspian
terns in the world. Predation on chum salmon is unknown but significant
predation by terns does occur on other salmonids.
During periods of low ocean productivity it is likely that only the populations
that use most productive freshwater habitats can remain productive.
Gorley Creek, an artificially created spawning channel which supported
~25% of the chum salmon in the Grays River, was lost due to flooding in
December 1999. If survival of spawners in the West Fork of the Grays River
and in the mainstem is low due to bed scour and sedimentation, the Gorley
channel may have contributed up to 50% of the natural production in the