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Green Sturgeon (Acipenser medirostris)

Status | Species Description | Habitat | Distribution | Population Trends | Threats | Conservat

Taxonomy | Key Documents | More Info

Status

ESA Threatened - Southern DPS

ESA Species of Concern - Pacific-northern DPS (including coastal spawning populations from the

River north to the Klamath and Rogue rivers)

CITES Appendix II - throughout its range

Species Description

Weight: up to 350 pounds (160 kg)

Length: average 4.5-6.5 feet (1.5-2 m), can be as long at 7 feet

Appearance:they have no scales, but they have five rows of characteristic bony plates on their bod

called "scutes"

Lifespan: 60-70 years

Diet: shrimp, mollusks, amphipods, and small fish

Behavior: anadromous; they live primarily in the sea and breed in fresh water

Green sturgeon are long-lived, slow-growing fish, and are the most marine-oriented of the sturgeon

species. Mature males range from 4.5-6.5 feet (1.4-2 m) in "fork length" and do not mature until th

at least 15 years old (Van Eenennaam, 2002), while mature females range from 5-7 feet (1.6-2.2 m

length and do not mature until they are at least 17 years old. They can weigh up to 350 pounds (160

Maximum ages of adult green sturgeon are likely to range from 60-70 years (Moyle, 2002).

Although they are members of the class of bony fishes, the skeleton of sturgeons is composed mos

cartilage. Sturgeon don't have scales, but they have five rows of characteristic bony plates on their 

called "scutes". The backbone of the sturgeon curves upward into the caudal fin, forming their sha

tail. On the ventral, or underside, of their flattened snouts are sensory barbels and a siphon-shaped

toothless mouth.

Green sturgeon are believed to spend the majority of their lives in nearshore oceanic waters, bays, 

estuaries. Younger green sturgeon reside in fresh water, with adults returning to freshwater to spaw

when they are about 15 years of age and more than 4 feet (1.3 m) in size. Spawning is believed to o

every 2-5 years (Moyle, 2002). Adults typically migrate into fresh water beginning in late February, a

spawning occurs from March-July, with peak activity from April-June (Moyle et al., 1995). Females

produce 60,000-140,000 eggs (Moyle et al., 1992). Juvenile green sturgeon spend a few years in fr

and estuarine waters before they leave for saltwater. They then disperse widely in the ocean.

The only feeding data we have on adult green sturgeon shows that they are eating "benthic"

invertebrates including shrimp, mollusks, amphipods, and even small fish (Moyle et al., 1992).

Habitat

Green sturgeon utilize both freshwater and saltwater habitat. Green sturgeon spawn in deep pools o

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Green Sturgeon Critical Ha

(click for larger view PDF

Green Sturgeon DPS M

Image: NOAA

(click for larger image)

"holes" in large, turbulent, freshwater river mainstems (Moyle et al., 1992). Specific spawning habitat

preferences are unclear, but eggs likely are broadcast over large cobble substrates, but range from clean

sand to bedrock substrates as well (Moyle et al., 1995). It is likely that cold, clean water is important for

proper embryonic development.

Adults live in oceanic waters, bays, and estuaries when not spawning. Green sturgeon are known to

forage in estuaries and bays ranging from San Francisco Bay to British Columbia.

Critical Habitat

In October 2009, NMFS designated critical habitat for the Southern DPS [pdf].

Distribution

This species is found along the west coast of Mexico, the United States, and Canada. Green sturgeon are

the most broadly distributed, wide-ranging, and most marine-oriented species of the sturgeon family. The

green sturgeon ranges from Mexico to at least Alaska in marine waters, and is observed in bays and

estuaries up and down the west coast of North America (Moyle et al., 1995).

The actual historical and current distribution of where this species spawns is unclear as green sturgeon

make non-spawning movements into coastal lagoons and bays in the late summer to fall, and because

their original spawning distribution may have been reduced due to harvest and other anthropogenic

effects.

Green sturgeon are believed to spawn in the Rogue River, Klamath River Basin, and the Sacramento

River. Spawning appears to rarely occur in the Umpqua River. Green sturgeon in the South Fork of the

Trinity River were thought extirpated (Moyle, 2002), but juveniles captured at Willow Creek on the Trinity

River (Scheiff et al., 2001) suggest that the fish could be coming from either the South Fork or the Trinity

River (Adams et al., in press). Green sturgeon appear to occasionally occupy the Eel River.

Population Trends

No good data on current population sizes exists and data on population trends is lacking. Tagging

experiments have been conducted irregularly since 1954, though regular tagging did not occur until 1990.

Over 500 green sturgeon have been captured and over 200 have been tagged.

Threats

The principal factor in the decline of the Southern DPS is:

reduction of the spawning area to a limited section of the Sacramento

Other threats to the Southern DPS include:

insufficient freshwater flow rates in spawning areas,

contaminants (e.g., pesticides)

bycatch of green sturgeon in fisheries

potential poaching (e.g., for caviar)

entrainment by water projects

influence of exotic species

small population size

impassable barriers

elevated water temperatures

Conservation Efforts

Fishing regulations and conservation measures represent a reduction in risk to green sturgeon. California,

Oregon, Washington (United States) and British Columbia (Canada) have restricted commercial and sport

fisheries where green sturgeon occur (IUCN Red List of Threatened Species ). Recent implementation

of sturgeon fishing restrictions in Oregon and Washington and protective efforts put in place on the

Klamath, Trinity, and Eel Rivers in the 1970s, 1980s, and 1990s may offer protection to the Southern

DPS. The recent closure of the California recreational fishery may also provide beneficial to this species.

The most important conservation currently occurring is the change in operations of Red Bluff Diversion

dam (open from mid September to mid May) allowing access to spawning areas above the dam.

Originally, the dam was closed year around.

5 foreign sturgeon speci

listed as endangered in

June 2014.

Green sturgeon are

anadromous fish. They l

primarily in the sea and 

fresh water.

There are 5 other ESA lis

sturgeon in the United S

shortnose sturgeon, Pal

sturgeon, Gulf sturgeon,

sturgeon, and Alabama

sturgeon.

Did You Know?

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Regulatory Overview

After completion of a study of its status (Adams et al., 2002) in 2002, NMFS determined that the green sturgeon is comprised of two DPS

qualify as species under the ESA, but that neither warranted listing as threatened or endangered [pdf] (68 FR 4433). Uncertainties in

structure and status of both DPSs led NMFS to add them to the Species of Concern List [pdf] (69 FR 19975).

The "not warranted" determination was challenged in April 2003. NMFS produced an updated status review in February 2005 and propo

the Southern DPS should be listed as threatened under the ESA. NMFS published a final rule in April 2006 listing the Southern DPS as

threatened [pdf] (71 FR 17757).

In September 2008, NMFS proposed critical habitat for the Southern DPS [pdf]. In October 2009, NMFS published the final rule to

designate critical habitat [pdf].

In May 2009, NMFS proposed a 4(d) rule [pdf] to apply ESA take prohibitions to the Southern DPS. NMFS published the final 4(d) rule

2010.

Taxonomy

Kingdom: Animalia

Phylum: Chordata

Class: Osteichthyes

Order: Acipenseriformes

Family: Acipenseridae

Genus: Acipenser

Species: smedirostris

Key Documents

(All documents are in PDF format.)

Title Federal Register Date

5-Year Status Review n/a 08/25/2015

Species of concern status review Pacific-Northern Green Sturgeon DPS n/a 11/20/2014

Initiation of 5-Year Review for the Southern DPS 77 FR 64959 10/24/2012

Final 4(d) Rule to Establish Take Prohibitions 75 FR 30714 06/02/2010

Critical Habitat for the Southern DPS Final Rule 74 FR 52300 10/09/2009

Proposed 4(d) Rule to Establish Take Prohibitions 74 FR 23822 05/21/2009

Proposed Critical Habitat for the Southern DPS 73 FR 52084 09/08/2008

Species of Concern Fact Sheet: Detailed n/a 11/02/2007

Fact Sheet Highlights

n/a 05/17/2007

Final ESA Listing Rule for Southern DPS 71 FR 17757 04/07/2006

Proposed ESA Listing for Southern DPS 70 FR 17386 04/06/2005

Status Review Update (2005) n/a 02/2005

2002 Status Review

n/a 06/2002

More Information

NMFS West Coast Regional Office Green Sturgeon Information

IUCN Species Information

References

Adams, P.B., C.B. Grimes, J.E. Hightower, S.T. Lindley, and M.L. Moser. 2002. Status Review for the North American green sturg

NOAA, National Marine Fisheries Service, Southwest Fisheries Science Center, Santa Cruz, CA. 49 p.

Adams, P.B., C.l. Grimes, J.E. Hightower, S.T. Lindley, M.L. Moser, and M.J. Parsley. In Press. "Population Status of North Ameri

Green Sturgeon <em>(Acipenser medirostris)</em> :: NOAA Fisheries http://www.fisheries.noaa.gov/pr/species/fish/green-sturgeon.html

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Green Sturgeon, Acipenser medirostris" Environmental Biology of Fishes.

Beamesderfer, R.C.P. and M.A.H. Webb. 2002 Green sturgeon status review information. S.P. Cramer and Associates, Gresham

U.S.

Moyle, P.B., P.J. Foley, and R.M. Yoshiyama. 1992. Status of green sturgeon, Acipensermedirostris, in California. Final Report su

to National Marine Fisheries Service. 11 p. University of California, Davis, CA 95616.

Moyle, P.B., R.M. Yoshiyama, J.E. Williams, and E.D. Wikramanayake. 1995. Fish Species of Special Concern in California. Seco

edition. Final report to CA Department of Fish and Game, contract 2128IF.

Moyle, P.B. 2002. Inland fishes of California. University of California Press, Berkeley, CA. 502 pp.

Scheiff, A.J., J.S. Lang, W.D. Pinnix. 2001. Juvenile salmonid monitoring on the mainstem Klamath River at Big Bar and mainste

River at Willow Creek 1997-2000. USFWS, AFWO, Arcata, CA 95521, 114 pp.

Van Eenennaam, J. P. 2002. Personnel Communication. In Adams, P.B., C.B. Grimes, J.E. Hightower, S.T. Lindley, and M.L. Mos

Status Review for the North American green sturgeon. NOAA, National Marine Fisheries Service, Southwest Fisheries Science C

Santa Cruz, CA. 49 p.

Updated: August 25, 2015

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Green Sturgeon <em>(Acipenser medirostris)</em> :: NOAA Fisheries http://www.fisheries.noaa.gov/pr/species/fish/green-sturgeon.html

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