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Soil Investigations for Data Collection in the Delta Initial Study/Proposed Mitigated Negative Declaration 85 The CCV steelhead evolutionarily significant unit (ESU) was listed as a threatened species under FESA on March 19, 1998 (USFWS 1998b). In addition, the species is also listed as threatened under the CESA. On November 4, 2005, the National Marine Fisheries Service (NMFS) proposed that all west coast steelhead be reclassified from ESUs to Distinct Population Segments (DPSs) and proposed to retain CCV steelhead as threatened (NMFS 2005b). On January 5, 2006, after reviewing the best available scientific and commercial information in a status review (Good et al. 2005), National Marine Fisheries Service (NMFS) issued its final rule to retain the status of CCV steelhead as threatened and applied its hatchery listing policy to include the Coleman National Fish Hatchery and Feather River Hatchery steelhead programs as part of the DPS (NMFS 2006b). In its latest 5-year status review, NMFS determined that the CCV steelhead DPS should remain classified as threatened. While various habitat restoration efforts, such as those in Clear Creek, appear to be benefitting CCV steelhead, the concerns raised in the previous status reviews remain. These concerns include low adult abundances, loss of spawning and rearing habitat, and a higher proportion of hatchery produced fish. As such, CCV steelhead remain listed as threatened and are likely to become endangered within the foreseeable future throughout all or a significant portion of its range. In addition, based on new genetic evidence by Pearse and Garza (2015), NMFS recommended that steelhead originating from the Mokelumne River Hatchery be added to the CCV steelhead DPS, as Feather River Hatchery fish are considered to be a native Central Valley stock and are listed as part of the DPS (NMFS 2016a). Steelhead have two life history types: stream-maturing and ocean-maturing. Stream-maturing steelhead enter fresh water in a sexually immature condition and require several months to mature before spawning, whereas ocean-maturing steelhead enter fresh water with mature gonads and spawn shortly after river entry. A variation of the two forms occurs in the Central Valley and primarily migrates into the system in the fall, then holds in suitable habitat until spawning during the winter and early spring (McEwan and Jackson 1996). Peak immigration seems to have occurred historically in the fall from late September to late October (Hallock 1989), with peak spawning typically occurring January through March (Hallock et al. 1961; McEwan and Jackson 1996). Unlike Pacific salmon, steelhead are capable of spawning more than once before death (Busby et al. 1996). Most juvenile steelhead spend two years rearing, although some spending less and a very few spending more (Hallock et al. 1961). Central Valley steelhead typically spend two years in the ocean before returning to their natal stream to spawn. About 70% of CCV steelhead spend 2 years within their natal streams before migrating out of the Sacramento-San Joaquin system as smolts, with small percentages (29%) and (1%) spending 1 or 3 years, respectively (Hallock et al. 1961). Juvenile steelhead smolts emigrate primarily from natal streams in response to the first heavy runoff in the late winter through spring (Hallock et al. 1961). Emigrating CCV steelhead use the lower reaches of the Sacramento and San Joaquin Rivers and the Delta as a migration corridor to the