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Soil Investigations for Data Collection in the Delta Initial Study/Proposed Mitigated Negative Declaration 90 HYD-1 and MM HAZ-1 through 4 would reduce potential impacts to Sacramento Splittail to: Less than Significant with Mitigation Incorporated. Longfin Smelt (Spirinchus thaleichthys) The Bay-Delta population of Longfin Smelt is designated as a candidate for listing under the FESA (USFWS 2012) and, since June 26, 2009, the Longfin Smelt is listed as threatened under the CESA. Longfin Smelt are anadromous and semelparous, moving from saline to brackish or freshwater for spawning from November to May (Moyle 2002; Rosenfield and Baxter 2007) Longfin Smelt usually live for 2 years, spawn, and then die (Rosenfield 2010). Peak spawning takes place in January and February of most years and appears to be centered in brackish water (1–8 ppt); their habitat typically extends from San Pablo Bay to the confluence of the Sacramento River and San Joaquin River. Newly hatched Longfin Smelt larvae are planktonic and probably do not control their position in the water column before they develop an air bladder. Once their air bladder is developed (~12 mm standard length) they are capable of controlling their position in the water column by undergoing reverse diel vertical migrations, which allows them to maintain position on the axis of the estuary (Bennett et al. 2002). The geographic distribution of larval and early juvenile life stages of Longfin Smelt may be influenced by freshwater inflows to the Delta during late winter and spring, although the mechanisms are complicated and not fully understood (Hieb and Baxter 1993; Baxter 1999; Dege and Brown 2004). Juvenile Longfin smelt move seaward, mostly west of Carquinez Bridge, by late summer and fall. Rosenfield and Baxter (2007) suggest that juvenile Longfin Smelt seek cooler and deeper water in the summer months. Overall, designated in-water work windows would reduce exposure of sensitive fish species, including Longfin smelt 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 Longfin Smelt to: Less than Significant with Mitigation Incorporated. Western Red Bat (Lasiurus blossevillii) Western red bat is identified as a CDFW Species of Special Concern. It is a medium bat with mottled reddish grayish pelage but can range from bright orange to yellow-brown, and short rounded ears. This species is locally common in some areas of California, occurring from Shasta County to the Mexico border, west of the Sierra Nevada/Cascade crest and deserts. Their winter range includes western lowlands and coastal regions south of San Francisco Bay.