Fall Chinook Redd Monitoring Report Calendar Year 2011
Chinook salmon (Oncorhynchus tshawytscha), also commonly referred to as king salmon, are the largest of the Pacific salmon (NMFS 1998, Netboy 1958). The Columbia River supports three major runs (spring, summer, and fall) of Chinook salmon generally based upon the season during which the adults re-enter the estuary to begin their upstream migration to spawn. Chinook salmon that spawn in the Hanford Reach of the Columbia River are fall-run fish. Fall-run Chinook salmon enter freshwater at an advanced stage of maturity, move rapidly to their spawning areas on the main stem or lower tributaries of the rivers, and spawn within a few days or weeks of freshwater entry (NMFS 1998, USFWS 1968, Healey 1991). Adult fall Chinook salmon destined for the Hanford Reach are upriver brights (URB), which enter the Columbia River in late summer and spawn in the fall. Spawning in the Hanford Reach typically begins in mid-October and lasts through November. From 1948 through 1988, the first-observation of spawning ranged from September 28 to October 26 with a median date of October 16 (PNL-7289). Females fan out nests or 'redds' in suitable gravel substrate and deposit eggs in an egg pocket while males simultaneously extrude milt to fertilize the eggs. Redds are readily identifiable at this time and appear as clean swept gravel patches amidst darker undisturbed substrate that is covered by algae (periphyton). 'Redd life' is a term applied to mean the period of time during which periphyton growth has not rendered the redd substrate indiscernible from the surroundings. Redd life is typically about six weeks on the Hanford Reach (PNL-7289).