ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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Splittail spawn in late April and May in Suisun Marsh and between early March and May in the upper Delta and lower reaches of the Sacramento and San Joaquin rivers. Spawning in the tidal freshwater habitats of the Sacramento-San Joaquin River Delta has been observed as early as January and as late as July(Sommer et. al 2002). Spawning occurs primarily in the lower reaches of rivers, flood bypasses, and dead-end sloughs. Little information is available as to how far upstream splittail occur in the San Joaquin River(Wang 1986),but adults and juveniles have been reported upstream of Modesto (USFWS 1996). Juvenile splittail are commonly found in Delta sloughs late in winter and spring. Splittail are believed to spawn at water temperatures from 487 to 68°F (Wang 1986). Juvenile emigration into the Delta begins in late winter(e.g.,February) and continues throughout the summer. In general,juvenile splittail are most abundant in water less than 6 feet deep,but show considerable capacity to swim against strong river and tidal currents (Moyle 2002).Although splittail use deeper, open water as they grow, much of the population continues to use shallow(<10 feet)edge habitat as adults (USBR and DWR 2003). Based on available information,the following temperature guidelines have been identified for Sacramento splittail: ► Optimal/suitable range: 41°F to 75°F ► Range of increasing adverse effects: 84°F to 91'F ► Lethal effects: >917; delta T of 7°F to 137 Hardhead Hardhead, a relatively large cyprinid species, is listed as a California Species of Special Concern;no federal designation has been made.Although this species is widespread and abundant throughout the Sacramento River and San Joaquin River systems,recent declines in numbers have raised concern. Hardhead are a moderately slow growing species that typically require two years to reach sexually maturity. Hardhead are typically found in streams having summer temperatures in excess of 68°F and reported suitable temperatures determined by laboratory experiments appear to be 75°F to 82°F (Moyle et al. 1995). However,in a natural thermal plume, hardhead generally selected temperatures of 637 to 707 when cooler temperatures were available(Moyle et al. 1995). Hardhead are typically found in low-to mid-elevation streams and reservoirs. In streams, adult hardhead tend to utilize the deepest portions of the water column,rarely moving into the upper water column,while juveniles demonstrated a preference for shallow water close to the stream banks (Moyle et al. 1995). Based on available information,the following temperature guidelines have been identified for hardhead: ► Optimal/suitable range: 63°F to 70°F ► Range of increasing adverse effects: > 82°F Striped bass Striped bass, a recreationally important introduced species, occurs in the Sacramento and San Joaquin rivers, major tributaries, and the Delta. Striped bass support a popular sport fishery in these water bodies. Adult spawning migrations extend from April through July with peak spawning activity occurring during late May and early June(Wang 1986).Adults spawn at or near the water surface in groups typically comprised of 5 to 30 fish. In the Sacramento River system, spawning is not initiated until water temperatures reach approximately 57°F, ceases at water temperatures exceeding 70°F, and the reported most favorable temperature range is 597 to 68°F (Moyle 2002). Initially, larval striped bass require currents to transport them to areas of slack water until the ability to swim is developed(1-2 days post-hatching). The emigration period lasts throughout the summer months and into early fall(e.g.,May—October)(LWA 2006). Striped bass are characteristic of a resident warm-water fish species with a relatively high thermal tolerance. The reported most favorable water temperatures for rearing juvenile striped bass range from approximately 61°F to EDAW Manteca WQCF and Collection System Master Plans EIR Fisheries and Aquatic Resources 4.13-10 City of Manteca