(CDFW, 2009; Miller and Lea, 1972). They have been collected in large numbers in Montezuma slough, Suisun Bay and near the Pittsburg and Contra Costa power plants. In the fall, adults from San Francisco and San Pablo Bays migrate to fresher water in the Delta to spawn. The spawning habits of longfin smelt are similar to the delta smelt and both species are known to school together. Larval stages are known to inhabit Suisun Bay and move south within the Bay-Delta as they grow larger in April and May (CDFW, 2009; Ganssle 1966). The larvae are pelagic and found in the upper layers of the water column. Data (CDFW, 2006) indicate that longfin smelt are present to a small extent in the Central Bay and are may be seasonally transient within the Brisbane Lagoon and shoreline of San Francisco Bay.
Green Sturgeon (Acipenser medirostris) Federally Threatened. Green sturgeon is the most widely distributed member and the most marine- oriented of North American sturgeons, entering rivers only to spawn. Adults (age 15 yrs. +) of the southern “distinct population segment” (DPS) of green sturgeon enter the Sacramento River in winter and spawn in spring and early summer; juveniles remain in fresh and estuarine waters for one to four years and then begin to migrate out to the sea (Moyle et al 1995, Moyle 2002, Israel et al. 2004). Sub-adult green sturgeon present in San Francisco Bay in summer are probably a mix of Northern and Southern DPSs (NOAA 2005b), although most of them are of the southern DPS (Israel et al. 2009). The summertime aggregations in San Pablo Bay, and in estuaries in general, are not associated with spawning (Lindley et al. 2008, Israel et al. 2009).
Although South Bay is not on the regular migration route of this species, green sturgeon are expected to occur in small numbers as strays in South Bay. It is not possible to estimate their abundance there, because no appropriate sampling programs exist for this large species, and the few small individuals that have been taken, e.g., in CDFW’s Bay study, do not provide a basis for quantitative estimation. Hearn et al. (2010) reported that known scientific collecting captures of green sturgeon were in or upstream of San Pablo Bay. At the time of their report, there were more than 400 acoustically tagged green sturgeon in the San Francisco Estuary, with the promise of increasing numbers in the future. Some of these fish have been detected at the San Francisco waterfront monitors, but not in the first two years of monitoring at an array in South San Francisco Bay near the Dumbarton Bridge (Tom Keegan, personal communication to A. Jahn, July 2011). It is possible, though it seems unlikely, that green sturgeon could occasionally wander into Brisbane Lagoon.
The southern Distinct Population Segment of the green sturgeon has federal threatened status, with the only known spawning habitat available in the upper Sacramento River.