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S AN L EANDRO T REATMENT W ETLAND P ROJECT S AN L EANDRO, A LAMEDA C OUNTY, C ALIFORNIA B IOLOGICAL A SSESSMENT A PRIL 2020 P:\TER2001\BA\San Leandro Treatment Plant BA 4‐7‐20.docx (04/07/20) 22 addressed in this BA in case it becomes listed during project implementation. Adult and juvenile longfin smelt occur in the open waters of estuaries, mostly in the middle or at the bottom of the water column. In the San Francisco Bay, the center of their distribution gradually moves down the estuary during summer. They concentrate in most years in the San Pablo Bay from April to June and become more dispersed in late summer. From June through October, juveniles and adults are uncommon to rare in the Delta (CDFG 2009). There is a gradual shift in population upstream in late fall and winter, as yearlings begin to move upstream to spawn. Longfin smelt range in freshwater is broadest during the November through April migration and spawning period (CDFG 2009). Spawning takes place in freshwater, over sandy or gravel substrates, rocks, and aquatic plants. In the San Francisco Bay, spawning occurs mainly downstream of Medford Island in the San Joaquin River. 3.2.3.2 Potential for Occurrence The tidal slough and surrounding harbor are not known as breeding grounds for this species. Stray individuals may occasionally venture near the project site from their primary migration route, but such movements are expected to be rare and short term in duration. No historical occurrences of longfin smelt have been recorded as part of the San Francisco Bay Study at the CDFW survey stations near the project site (CDFW 2018). 3.2.4 Western Snowy Plover 3.2.4.1 Status and Biology The Pacific Coastal distinct population segment of the western snowy plover is listed as threatened under the federal Endangered Species Act. Western snowy plovers were historically widely distributed along the California coast but have undergone significant declines in recent decades (USFWS 2007). Western snowy plovers are typically found in open, sparsely vegetated habitats, most commonly on beaches. During the winter they may be found on beaches they do not nest on, as well as manmade salt ponds, and estuarine sand and mud flats (USFWS 2007). In the winter, western snowy plovers are gregarious, sometimes congregating in large flocks on beaches and other open areas. During the breeding season, western snowy plovers nest primarily on coastal beaches above the high‐tide line, including sand spits, dune‐backed beaches, and other coastal features where vegetation is sparse (USFWS 2007). Nests are placed in shallow depressions created by males. Nesting areas typically have some vegetation or washed up debris, such as kelp or drift wood, which provide shelter from winds and predators and/or provide foraging habitat. 3.2.4.2 Potential for Occurrence Western snowy plovers could briefly fly through or forage at the project site. This species could forage in the tidal slough and basin, although this species is unlikely to nest in the Action Area due to the limited habitat present. They could possibly nest in the basin if water is not present during the nesting season (March 1 through September 30), but they are not likely to nest in the basin due to limited suitable habitat and the long period in which the basin is inundated with water. The closest breeding occurrence is a 1979 record approximately 0.3 mile from the site at Bay Farm Island (CDFW 2020). This species was observed at the Oyster Bay Regional Shoreline in January 1984 (eBird 2020) and has been recorded at the Oakland International Airport (Bloom, pers. comm.).