EPA's Vessel General Permit and Small Vessel General

Threats
Natural Threats. Birds and larger freshwater fish feed on eggs and larvae, while sharks,
pinnipeds and other large predators prey on marine adult and subadult fish.
Anthropogenic Threats. In general sturgeon have declined from the combined effects from the
construction of dam and water diversion projects, dredging and blasting, water pollution and
fisheries. The longevity, slow rate of growth, delayed maturation, and bottom-feeding habits of
sturgeon makes them susceptible to over-harvest and exposure to (and the accumulation of)
contaminants. Many sturgeon also do not spawn on an annual basis, but may spawn every other
year or even more infrequently. Thus even small increases in mortality can affect population
productivity (Heppell 2007). While sturgeon will be exposed to dissolved contaminants in the
water column their body form, feeding habits and affinity with bottom sediments may expose
them to a different suite of contaminants than pelagic fish. The sediment exposure pathway may
be more significant. Benthic dwelling fish such as sturgeon may be exposed through the direct
contact with sediment and its boundary layer and commonly have a higher rate of exposure
through incidental ingestion.
Southern Green Sturgeon
Green sturgeon occur along the west coast of North America from Mexico to the Bering Sea
(Adams et al. 2002, Colway and Stevenson 2007). Distinguished primarily according to genetic
differences and spawning locations, NMFS recognizes two species of green sturgeon: a northern
species whose populations are relatively healthy, and a Southern species that has undergone
significant decline (Adams et al. 2007). NMFS listed the Southern species of green sturgeon as
threatened in 2006 (71 FR 17757).
Green sturgeon are considered one of the most marine-oriented sturgeon species, spending much
of their lives in coastal marine waters, estuaries and bays. Early life stages rear in fresh water,
and adults return to fresh water when they are 15 years old or older to spawn. Across the species’
range only three rivers contain documented spawning (Moyle et al. 1992, CDFG 2002). Outside
of natal rivers, the distribution of southern green sturgeon and northern green sturgeon overlap.
Both the northern species and southern species of green sturgeon occupy coastal estuaries and
coastal marine waters from southern California to Alaska, including Humbolt Bay, the lower
Columbia River estuary, Willapa Bay, Grays Harbor and southeast Alaska. In general, green
sturgeon are more common north of Point Conception, California.
Green sturgeon are spring spawners and initiate spawning migrations as early as March. Fish in
the Klamath River have been observed initiating migrations between April and June, Rogue
River fish between May and July, whereas Heubein et al., (2009) observed Sacramento River
fish making their upstream migrations between March and April. Spawning generally occurs in
deep pools of large rivers or off-channel coves (Moyle et al. 1992, Moyle et al. 1995, Rien et al.
2001, Heublein et al. 2009). Fish then tend to aggregate in deep pools, where they will oversummer
before outmigrating in the fall, although some fish have been observed outmigrating
relatively soon after presumed spawning events (Heublein et al. 2009). In the Sacramento River
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