In 1998 we continued to investigate the use of small tributaries of the Sacramento River by juvenile chinook salmon. Although the unusual water conditions brought about by el Nino limited some aspects of the study, we were able to document use of 26 Sacramento River tributaries for non-natal rearing. Continual fluctuations in stream discharge resulted in more movement by the juveniles than observed in 1997. Consequently upstream movement was greater than in 1997, probably as high as would ever be expected. Unfortunately, the continual movement made growth estimation impossible due. As in former years, a variety of sizes were present, and by inference, a variety of races. DNA analysis was used to confirm the presence of the listed winter race in Mud Creek. The tributary-rearing juveniles were in excellent condition, comparable to that of former years when they were shown to be in better condition than river-rearing juveniles. Comparison with condition factors obtained for river-juveniles by CaDFG personnel proved infeasible due to differences in methodology. The total population rearing in tributaries was estimated to be between 100,000 and 1,000,000.
This work was made possible by Grant # 1448-0001-96729 from the U.S. Fish and Wildlife Service under the authority of the Federal Grant and Cooperative Agreement Act of 1977 and the Central Valley Improvement Act.