Acipenser medirostris
Adult green sturgeon in Klamath River, CA. Photo: Thomas Dunklin
Adult green sturgeon in Klamath River, CA. Photo: Thomas Dunklin
Green sturgeon are an anadromous fish, which means they can live in both fresh and saltwater. They have a relatively complex life history that includes spawning and juvenile rearing in rivers followed by migrating to saltwater to feed, grow, and mature before returning to freshwater to spawn. They are a long-lived, slow-growing fish. They are vulnerable to many stressors and threats including blocked access to spawning grounds and habitat degradation caused by dams and culverts. The southern distinct population segment is listed as threatened under the Endangered Species Act.
NOAA Fisheries is committed to conserving and protecting green sturgeon. Our scientists and partners use a variety of innovative techniques to study, learn more about, and protect this species.
Twenty-seven species of sturgeon can be found in temperate waters of the Northern Hemisphere. Two of them reside on the West Coast of North America: the green sturgeon (Acipenser medirostris) and the white sturgeon (Acipenser transmontanus).
NOAA Fisheries received a petition in June 2001 from several environmental organizations requesting that the agency list the North American green sturgeon under the Endangered Species Act. On April 7, 2006, we listed the southern distinct population segment, or sDPS, of North American green sturgeon as threatened under the ESA. Critical habitat was designated on October 9, 2009. On June 2, 2010, NOAA Fisheries published final ESA protective regulations 4(d) for the southern distinct population segment of North American green sturgeon. We released a final environmental assessment analyzing the environmental impacts of these ESA Section 4(d) rules.
Sturgeons are most closely related to paddlefish, reedfish, and numerous fossil groups within the infraclass Chondostei. These are primary cartilaginous fish with some degree of bony structures (ossification). They are not ancestral to modern bony fishes but represent a highly specialized and successful offshoot of ancestral Chondosteans. Their skeletons are composed of cartilage, and they have a series of external bony plates called scutes along their backs and sides.
Sturgeon are often likened to sharks because of the many features they share, including:
Sturgeon do not have teeth. Instead, they use their long, flexible "lips" (i.e., protrusible jaw) to suck up food from the bottom.
Identification Guide (PDF, 1 page)
Green sturgeon were first described in San Francisco Bay in 1857. Like most sturgeon, they are anadromous but tend to spend more time in the ocean than most species. They can be found from Alaska to Mexico but are most commonly encountered north of Point Conception, California. They differ from white sturgeon in their olive green coloration, barbell placement, vent placement, differences in number and sharpness of scutes, and presence of an additional scute behind the dorsal and anal fins.
Green sturgeon reach maturity around age 15 and can live to be 70 years old. Unlike salmon, they may spawn several times during their long lives, returning to their natal rivers every 3–5 years. By comparing the DNA and movement patterns of tagged fish, researchers identified two genetically distinct population segments of green sturgeon. Although these fish may look identical, their genetic makeup is very different. This distinction allows NOAA Fisheries and other agencies to manage populations more effectively and helps preserve diversity.
Fish that spawn in the Klamath and Eel River in Northern California and the Rogue River in Oregon belong to the Northern DPS (nDPS). NOAA Fisheries lists them as a Species of Concern. Fish that spawn in the Sacramento, Feather, and Yuba River in California belong to the federally threatened southern DPS (sDPS).
During spawning runs, adult sDPS fish enter San Francisco Bay between mid-February and early May and migrate rapidly up the Sacramento River. Spawning occurs in cool sections of the upper Sacramento River where there are deep, turbulent flows and clean, hard substrate. In the autumn, these post-spawn adults move back down the river and re-enter the ocean. After hatching, larvae and juveniles migrate downstream toward the Sacramento-San Joaquin Delta and estuary. After rearing in the delta and estuary for a few years, they move out to the ocean. As adults, both population segments of green sturgeon migrate seasonally along the West Coast. They congregate in bays and estuaries in Washington, Oregon, and California during the summer and fall months. During winter and spring months they congregate off of the northern Vancouver Island in British Columbia, Canada.
Green sturgeon populations successfully persisted throughout North America for 200 million years. They are thought to have experienced a precipitous decline during the past century. Harvest of adults likely resulted in direct declines in abundance and destruction of spawning and rearing habitats led to reduced population sizes and resilience. There are now regulations prohibiting harvest or take in effect. The most significant threats to green sturgeon likely relate to loss and inaccessibility of available spawning habitat. Much of this is driven by competing water resource needs between humans and fish.
Dams, altered flows, and entrapment in water diversions can impede or inhibit their migration. Other threats to the survival and recovery of this ancient fish include:
Insufficient freshwater flow rates in spawning areas
Containments.
Fisheries bycatch.
Poaching.
Invasive species.
Impassable barriers.
Unfavorable water conditions.
An important step in barrier removal was the decommissioning of the Red Bluff Diversion Dam (rkm 391 on the Sacramento River) in 2013. With the permanent raising of the gates, passage to spawning grounds is now accessible for adult sDPS green sturgeon. Larvae and juvenile sDPS green sturgeon have been collected by USFWS Red Bluff every year since the dam was decommissioned. USFWS Red Bluff tags juvenile sDPS green sturgeon in the fall to understand juvenile migration rates from the Sacramento River into the Sacramento-San Joaquin Delta.
In 2019, the California Department of Water Resources (DWR) improved fish passage for salmonids and sturgeon entering the Yolo Bypass from the Sacramento and Feather rivers. The improved Fremont Weir fish passage facility allows for the volitional passage of adult sturgeon onto the Yolo Bypass during weir overtopping events. California DWR is continuing to improve fish passage and increase floodplain rearing habitat in the Yolo Bypass.
View the Fremont Weir Adult Fish Passage Project video on YouTube.
| Kingdom | Animalia | Phylum | Chordata | Class | Osteichthyes | Order | Acipenseriformes | Family | Acipenseridae | Genus | Acipenser | Species | medirostris |
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