Fall Chinook Salmon Redds

The Hanford Reach remains the most important natural spawning area for fall chinook salmon in the main-stem Columbia River. Chinook salmon are an important resource in the Pacific Northwest; they are caught commercially and for recreation. Salmon are also of cultural importance to Native American tribes. Salmon redds have been surveyed since 1948 to assess the condition and status of this species with respect to Hanford Operations. The salmon in the Hanford Reach area are classified as the upriver bright (URB) race of fall chinook salmon (Oncorhynchus tshawytscha ). Fall chinook salmon migrate upstream to spawning areas in the Hanford Reach from mid-August through October, they dig redds and deposit eggs from late October to late November. The Hanford Reach is a 90-km segment of the Columbia River extending from the upper end of McNary Dam Reservoir (near the downstream border of the Hanford Site) to Priest Rapids Dam.

One to seven aerial surveys are flown each year at approximately weekly intervals from late September to November. Newly excavated redds appear as light-colored, regularly shaped circular or oval areas that contrast with the normally darker periphyton-covered substrate. The redds remain visible for about 6 weeks before their surface becomes recolonized by algae growth. For this reason, some redds counted at the beginning of the spawning period may not be visible by the end of the season. It should be noted that aerial surveys do not yield absolute counts of redds because visibility varies, depending on water depth and other factors, and because the number of redds in high-density locations cannot be counted accurately However, redd survey data generally agree well with adult escapement figures obtained by counting migrating adult fish at fish ladders on the Columbia River.

Additional information can be found in: "Spawning and abundance of fall chinook salmon (Oncorhynchus tshawytscha) in the Hanford Reach of the Columbia River, 1948-1988" by D.D. Dauble and D.G. Watson, March 1990, PNL-7289.

Summary of peak redd counts for fall chinook salmon (Oncorhyncus tschawytscha) in the Hanford Reach. Redd surveys conducted from October through November annually using fixed-wing aircraft.