EPA's Vessel General Permit and Small Vessel General

adult green sturgeon spawn in late spring and early summer (Heublein et al. 2009). It appears
that specific habitat for spawning includes large cobblestones (where eggs can settle between),
although spawning is known to occur over clean sand or bedrock.
Green sturgeon are a long-lived fish and likely live for 60 to 70 years (Moyle 2002). Age at first
maturation for green sturgeon is at least 15 years old, after which adults likely return every 2 to 5
years to spawn (Adams et al. 2002, Van Eenennaam et al. 2006). Most male spawners are young
(17 to 18 years) while females on the spawning grounds are often older (27 to 28 years).
Green sturgeon spend their first 1 to 4 years in their natal streams and rivers (Nakamoto et al.
1995, Beamesderfer and Webb 2002), although they are believed to be physiologically adapted
to sea water survival at 6 months of age (Allen and Cech 2007, Allen and J.J. Cech 2007, Allen
et al. 2009). Larvae are active at night, a behavior that likely reduces predation and avoids being
moved downstream more than necessary (Cech Jr. et al. 2000). Green sturgeon larvae grow very
rapidly, reaching about 300 mm by age one (Deng 2000). While in fresh water, juveniles feed on
a variety of fishes and invertebrates (Moyle et al. 1992). One juvenile from the Sacramento-San
Joaquin estuary was found to have preyed most commonly upon opisthobranch mollusks
(Philline sp.), with bay shrimp (Crangon sp.) and overbite clams (Potamocorbula amurensis) as
secondary prey. Other juveniles in the Sacramento River delta feed on opossum shrimp
(Neomysis mercedis) and Corophium amphipods (Radtke 1966).
Upon outmigration from fresh water, subadult green sturgeon disperse widely along through
continental shelf waters of the west coast within the 110 meter contour (Moyle et al. 1992,
Erickson and Hightower 2007). It appears that green sturgeon generally distribute north of the
river mouth from whence they emerge as juveniles during fall and move into bays and estuaries
during summer and fall (Moser and Lindley 2007, Israel et al. 2009). The limited feeding data
available for subadult and adult green sturgeon show that they consume benthic invertebrates
including shrimp, clams, chironomids, copepods, mollusks, amphipods and small fish ((Houston
1988, Moyle et al. 1992). Sturgeon use electroreception to locate prey. Olfaction and taste may
also be important to foraging, while vision is thought to play a minor role in prey capture (Miller
2004).
Status and Trends
NMFS listed the southern population of the North American green sturgeon as threatened on
April 7, 2006 (71 FR 17757). Trend data for green sturgeon is severely limited. Available
information comes from two predominant sources, fisheries and tagging. Only three data sets
were considered useful for the population time series analyses by NMFS’ biological review
team: the Klamath Yurok Tribal fishery catch, San Pablo sport fishery tag returns and Columbia
River commercial landings (NMFS 2005c). Using San Pablo sport fishery tag recovery data, the
California Department of Fish and Game produced a population time series estimate for the
southern species. San Pablo data suggest that green sturgeon abundance may be increasing, but
the data showed no significant trend. The data set is not particularly convincing, however, as it
suffers from inconsistent effort and since it is unclear whether summer concentrations of green
sturgeon provide a strong indicator of population performance (NMFS 2005c). Although there is
not sufficient information available to estimate the current population size of southern green
sturgeon, catch of juveniles during State and Federal salvage operations in the Sacramento delta
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