Contributions to the Biology of Central Valley Salmonids 217 Studies of Spawning Habitat for Fall-Run Chinook Salmon in the Stanislaus River Between Goodwin Dam and Riverbank

The spawning habitat of fall-run chinook salmon (Oncorhynchus tshawytscha) was studied in the Stanislaus River between Goodwin Dam and Riverbank between 1994 and 1997 to evaluate whether hab-itat quality was potentially limiting the population and whether two restoration projects improved spawning conditions. Redd surveys in 1994 and 1995 indicated that spawning was concentrated in the riffles located in the 12-mile reach between Goodwin Dam and Orange Blossom Bridge. Most of the spawning (73%) occurred upstream of the riffles ’ crests where the streambed gradient was positive (for example, the tail of a pool). Sample areas were divided into the upper, middle, and lower portions of riffles to determine why the salmon used the upper areas. Substrate samples collected from the upper six inches of the stre-ambed indicated that predicted survival probabilities for chinoo