California Sturgeon Conservation

Sturgeon are members of Family Acipenseridae, an ancient lineage of bony fishes that coexisted with the dinosaurs. The group, which also includes paddlefishes, diverged from other fishes at least 200 million years ago in the early Jurassic period. There are 25 species of sturgeon worldwide, two of which, White (Acipenser transmontanus) and Green (A. medirostris), are native to California. Both species are at risk and are a focus of state management and conservation efforts.

Biology

Diagram of sturgeon life cycle - click to enlarge in a new tab
Click/tap to enlarge in new tab
White Sturgeon underwater over cobble
Adult White Sturgeon. CDFW photo by Mike Healey.
Green Sturgeon underwater over cobble
Adult Green Sturgeon. CDFW photo by Mike Healey.

Although they are a bony fish (Class Osteichthyes), rather than a cartilaginous fish like sharks (Class Chondrichthyes), sturgeon actually have very little true bone. Most of their internal skeleton is composed of cartilage, as in sharks. Bone is mostly restricted to plates around the head, the spines of the pectoral fins, and the heavy armor-like scales called scutes that line their body. Sturgeon have been referred to as living fossils because they retain a number of physical traits that are thought to represent the ancestral condition of fishes. These include a heterocercal tail in which the vertebrae extend into an upper lobe that is longer than the lower lobe, a spiral valve intestine, and electroreceptors similar to sharks. Their mouth is also unique and is thought to have evolved separately from other fishes, forming a toothless, extendible tube that is good for sucking food items up off the bottom. Sturgeon have no teeth as adults, instead food is swallowed whole. Their diet usually includes bottom-dwelling crustaceans such as amphipods, shrimp, and crabs, as well as bivalves, fishes, and fish eggs.

Sturgeon are large, very long-lived and late to mature. All sturgeon are migratory, typically spending most of their adult lives in estuaries, the lower reaches of rivers, or the ocean. They migrate upstream in large freshwater rivers to spawn in cool, deep, swift flowing river reaches over gravel and cobble bottoms. Sturgeon do not die after spawning like Pacific salmon, and the both species are capable of repeated migrations every 2-6 years. Juvenile sturgeon remain in the river for a period of time before migrating to the estuary or bay.

Video of Green and White Sturgeon underwater

Threats

Unfortunately, the life-history traits of sturgeon make them very vulnerable to human impacts.

  • Fish ladders designed for salmon are not effective at passing sturgeon, so dams and water diversions can impede migration and block ancestral spawning grounds.
  • Changes to river hydrology can impact water quality, such as temperature or dissolved oxygen, which may particularly harm sensitive life-stages such as eggs or larvae.
  • Changes to how rivers are managed can also degrade necessary spawning habitat by increasing siltation, covering the coarse gravel and cobble substrates that sturgeon require for spawning.
  • Early life stages are entrained into water diversions.
  • Pollution from runoff, predation, or changes to the food web from introduced non-native species may impact these fishes.
  • Harmful Algal Blooms, such as the one in San Fransisco Bay in 2022, cause mass mortality events.

Sturgeon have historically been sought after in fisheries, both for their meat and for eggs for caviar. Because they are so slow to reproduce, they are very sensitive to overfishing and require careful management.

Status in California

White Sturgeon are a candidate species for listing as Threatened under the California Endangered Species Act (CESA). More information about what that means can be found under the White Sturgeon species page.

Green Sturgeon from the southern population were listed as threatened under the federal Endangered Species Act in 2006. Northern population Green Sturgeon are not state or federally listed, but they both are categorized as a state Species of Special Concern. More information about what that means can be found under the Green Sturgeon species page.

The American Fisheries Society considers the survival of sturgeon to be dependent on conservation measures taken to protect them. Worldwide, sturgeon are considered the most threatened group of animals on the IUCN Red List of Threatened Species, with 85% species considered to be at risk of extinction.

Conservation Partners

CDFW is actively engaged in efforts to conserve and improve sturgeon populations in California. These projects often involve collaboration with federal, state, academic, and non-government partners. 

CDFW has directed scientists to identify, and address population decline from non-fishing sources. This includes developing conditions to avoid, minimize, or mitigate impacts to Green and/or White sturgeon that could be required on projects that affect sturgeon. CDFW will use these conditions along with project-specific analyses when permitting various activities such as transportation, development, and water infrastructure.

Since White Sturgeon became a candidate species under CESA, CDFW has worked with the California Department of Water Resources (DWR) to amend the existing Incidental Take Permit for the State Water Project (SWP). The amendment increases requirements for avoidance, minimization, and other mitigation measures. DWR also will invest in a Science Plan for the species, invest in new monitoring around the SWP impacts, increase entrainment and salvage monitoring to deal with risks to White Sturgeon, and develop a risk assessment process that can respond to entrainment of juvenile sturgeon and alter operations to reduce take.

In addition to the projects described below, other efforts include monitoring habitat quality and studying sources of adult mortality, such as vessel strikes or predation.

Monitoring Sturgeon Populations

Population monitoring is critical to provide an accurate estimate of population size, habitat use, and spawning efforts. Learn more about some of the current population evaluation methods below:

Setline Survey

The Department is currently engaged in a robust mark-recapture survey in San Francisco Bay and the Delta to provide an accurate estimate of the current white sturgeon population. This survey is independent of sturgeon report card data and is adapted from established methods used in Oregon and Washington. CDFW initiated this new pilot White Sturgeon monitoring program in May 2024. The program uses a mark-recapture design, which is a common tool in fishery management. In this method, fish are captured, given a permanent mark, released to mix back into the population, and then recaptured several months later. The proportion of new vs. previously marked fish caught during the recapture phase can be used in models to estimate the total number of fish in the population. In this new program, White Sturgeon are captured throughout the Bay-Delta region using anchored setlines. Each fish is measured and marked with a PIT tag (the same kind of tag used to microchip pets) that will last for the entire long life of the fish. Capture, marking, and scanning of fish is conducted by a collaboration between boat captains from the sturgeon fishing guide community and CDFW and Pacific States Marine Fisheries Commission scientists.

Guide Tagging Program

In addition to the Setline Survey, CDFW has also partnered with guides and boat captains from the sturgeon fishing community to collect data from fish they capture with clients. Participants are trained and supplied with data collection tools. They are asked to measure, scan, and photograph all sturgeon caught by clients. This program permits guides to use their fish catching knowledge and expertise to help the Department collect data that will inform future management and conservation efforts.

Report Cards

Data from report cards provide information on the number of White and Green sturgeon caught, catch per angler, and summaries of temporal (month or season) and spatial (catch location) fishing pressure (i.e., number of anglers). After Report Cards are returned, CDFW compiles all Card data from the previous season and produces a technical report. The resulting report summarizes data from the previous Card season in comparison with past Card seasons. Visit our Sturgeon Report Card page for access to the most recent report (PDF), as well as past reports.

Tracking Sturgeon Movement

Telemetry

Adult White Sturgeon and juvenile southern DPS Green Sturgeon are captured by CDFW staff and fitted with acoustic tags. These tags serve to track individuals for long periods of time across a wide range of habitats from the bay delta and up rivers. This helps inform the rearing and migration patterns for both species and improve management. Mature White Sturgeon are especially monitored for spawning migration during various water outflow conditions/water year types.  Learn more about acoustic tagging in the Green Sturgeon Telemetry Report (PDF).

Sonar Survey

CDFW and Pacific States Marine Fisheries Comission look for spawning sturgeon on rivers during spawning season. This supports the telemetry efforts and helps define important spawning locations, and may provide rough indexes of annual spawning activity. Learn more about how CDFW uses sonar. 

Rescue Efforts

Sturgeon may be stranded on floodplains and bypasses after high flow events. Once flood waters recede, sturgeon may become trapped in deep holes where they are cut off from access to the river. CDFW staff are aware of frequent stranding locations and regularly conduct seasonal rescue efforts to prevent the mortality these fish would otherwise face.

What can you do?

You can assist the Delta ecosystem and sturgeon recovery in several ways:

Sturgeon Carcass Reporting

Researchers studying the causes of death of adult sturgeon (PDF) request that any observations of sturgeon carcasses be reported to CASturgeonResearch@gmail.com.

Provide as much information as possible including:

  • Detailed location (such as GPS coordinates, landmarks, cellphone map app screenshots).
  • Pictures (please include common items for scale such as coins or dollar bills, beverage can, etc.).
  • Do not move or damage the carcass. Specialists will locate the carcass and take measurements and samples as part of this ongoing monitoring study.

Fisheries Branch
Branch Chief: Jay Rowan
1010 Riverside Parkway, West Sacramento, CA 95605
Fisheries@wildlife.ca.gov