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Soil Investigations for Data Collection in the Delta Initial Study/Proposed Mitigated Negative Declaration 87 size of fry migrants at approximately 40 millimeters between December and April in Mill, Butte, and Deer Creeks reflects a prolonged emergence of fry from the gravel (Lindley et al. 2004). Studies in Butte Creek found that the majority of CV spring-run Chinook salmon migrants are fry occurring primarily during December, January, and February, and that fry movements appeared to be influenced by flow (Ward et al. 2002, 2003; McReynolds et al. 2005). Small numbers of CV spring-run Chinook salmon remained in Butte Creek to rear and migrated as yearlings later in the spring. Juvenile emigration patterns in Mill and Deer Creeks are very similar to patterns observed in Butte Creek, with the exception that juveniles from Mill and Deer creeks typically exhibit a later young-of-the-year migration and an earlier yearling migration (Lindley et al. 2006). Peak movement of yearling CV spring-run Chinook salmon in the Sacramento River at Knights Landing occurs in December, and is high in January, tapering off through the middle of February; however, juveniles were also observed between November and the end of February (Snider and Titus 2000). Overall, designated in-water work windows would reduce exposure of sensitive fish species, including Chinook salmon, and life stages to in-water work activities. The activities of the Proposed Project would be minor in scope and would not result in degradation of aquatic habitat or water quality conditions and any potential effects related to potential increase in suspended sediment concentrations and contaminants due to disturbance of the river bed would be negligible. Implementation of Mitigation Measures MM BIO-14, along with MM HYD-1 and MM HAZ-1 through 4 would reduce potential impacts to CV spring- run Chinook salmon to: Less than Significant with Mitigation Incorporated. Sacramento River winter-run ESU of Chinook Salmon (Oncorhynchus tshawytscha) The Sacramento River winter-run Chinook salmon ESU was initially listed as a threatened species in August 1989, under emergency provisions of the federal Endangered Species Act (FESA) (NMFS 1989) and was listed as threatened in a final rule in November 1990 (NMFS 1990). The ESU consists of only one population confined to the mainstem of the upper Sacramento River in California’s Central Valley below Keswick Dam. The ESU was reclassified as endangered under the FESA on January 4, 1994 (NMFS 1994), because of increased variability of run sizes, expected weak returns as a result of two small year classes in 1991 and 1993, and a 99% decline between 1966 and 1991. The National Marine Fisheries Service (NMFS) reaffirmed the listing of the Sacramento River winter-run Chinook salmon ESU as endangered on June 28, 2005 (NMFS 2005c) and included winter-run Chinook salmon in the Livingston Stone National Fish Hatchery artificial propagation program in the ESU. In addition to the federal listing, Sacramento River winter-run Chinook salmon are listed as endangered under the CESA. Sacramento River winter-run Chinook salmon adults enter the Sacramento River basin between December and July; the peak occurs in March (Yoshiyama et al.