The Sandy River Basin is home to several species of fish, including spring and fall Chinook salmon, coho salmon, and winter steelhead. These salmon and steelhead, which historically numbered in the tens of thousands, were listed as threatened species under the Endangered Species Act (ESA) in the late 1990s.
The salmon and steelhead populations that are native to the Sandy River have declined in the past century. The decline can be attributed to multiple factors, but the increase in human population, and degradation of habitat are major contributors. Available information suggests that current adult returns are only 10-25 percent of historic levels.
The Sandy River is still a key salmon tributary to the lower Columbia River, offering relatively high quality habitat. Most of the watershed is federal land and in good condition. The Sandy is especially significant for the fall Chinook and coho populations because the river supports one of only two remaining populations for each species with appreciable natural production in the lower Columbia River.
Fall Chinook – The Sandy River is one of only two rivers of the Lower Columbia River that supports appreciable natural production of fall Chinook salmon. Most juvenile fall Chinook salmon typically spend only a brief time in the Sandy River before migrating to the ocean. Most adult fish stay in the ocean three or four years before returning to spawn. Typically, adults return to the Sandy River Basin in August and spawn from October through December. As the maps included in the atlas show, fall Chinook were historically found in the Basin far upstream in the Salmon, Zigzag, and upper Sandy Rivers as well as in the Little Sandy and the Bull Run rivers. Today, runs of fall Chinook occur in the rivers below Marmot, Little Sandy, and Bull Run dams, and spawning occurs primarily in the mainstem Sandy River and its tributaries near Oxbow Park.
Spring Chinook - Historically, strong native runs of spring Chinook utilized habitat throughout the Sandy River Basin. Since the early 1900s, hatchery spring Chinook have been released into the river and most returning fish are thought to be of hatchery origin. Natural production still occurs, primarily upstream of Marmot Dam. Adult spring Chinook return as early as February, but, more commonly, the large silvery fish appear in April and May. Today, spring Chinook in the Basin use the mainstem Sandy River from the mouth all the way up to the larger streams in the upper watershed for migration, spawning, and rearing. The Marmot and Bull Run dams have blocked access to upstream river areas. Spring Chinook rearing and spawning are also affected by high water temperatures in the mainstem Sandy River below Marmot Dam and in the lower Bull Run River.
Winter Steelhead – Most steelhead from the Sandy River migrate to the ocean after two to three years. The fish spend several years there before returning to spawn from February through May. Young winter steelhead are present year-round throughout most of the Sandy River mainstem in both the upper and lower portions of the Basin. Winter steelhead primarily spawn and rear in their historic habitat which extends upstream of Marmot Dam in the Salmon River, its tributaries, and in Still Creek. Other waterways in the Basin that support winter steelhead include the Bull Run River and Gordon, Trout, and Buck creeks. Decreases in steelhead abundance can be attributed to loss of habitat diversity and quantity, increased sediment loads, and obstructions from dams.
Coho – The Sandy River is one of only two rivers in the lower Columbia River region that supports appreciable natural production of coho salmon; the other is the Clackamas River. Historically adult coho returned from October through February, culminating in a peak spawning season that lasted from November through February. With the exception of reaches upstream of Bull Run and the Little Sandy dams, coho distribution has changed little from historical conditions. The majority of suitable coho spawning and rearing habitat in the Sandy River is located upstream of Marmot Dam in the mainstem Sandy River, in the Salmon River below Final Falls, and in Still Creek. Lower Basin tributaries that may support coho include Cedar, Trout, Beaver, Gordon, and Buck creeks. Coho populations have been affected by dwindling habitat diversity and quantity, obstructions caused by dams, and reduced stability of the stream channel.
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