Acipenser transmontanus
Distribution
White Sturgeon are native to the West coast of North America, where they may be found in coastal waters from Ensenada, Mexico, to Alaska. Although occasionally found in the ocean, they primarily reside in large rivers and their associated estuaries, including the Sacramento-San Joaquin system in California, the Fraser River (British Columbia), and the Columbia River and its tributaries (Washington and Oregon). White Sturgeon in the Sacramento-San Joaquin system represent the southernmost spawning population of the species. Some spawning has recently been documented in the San Joaquin River, and may also occur in tributaries including the Feather, Yuba, and Bear rivers. Small runs may exist on the Russian, Klamath, Trinity, and Eel rivers, but it is not known if successful spawning occurs in those rivers.
Life history and ecology
White Sturgeon are the largest freshwater fish in North America. There are historical records of fish as large as 610 cm, although it is now rare to encounter fish larger than 200 cm in Californian waters. The average White Sturgeon captured in the Delta in recent years is approximately 109 cm. As with all Acipenserids, White Sturgeon are long-lived. The oldest fish on record was 103 years old at the time of capture, but most fish in the Delta are now believed to be less than 20 years old. Age at first reproduction is approximately 10-16 years old, with males maturing earlier and at a smaller size than females. Females produce an average of 5648 eggs per kilogram of body weight, and a 60 inch individual averages over 200,000 eggs. Males may spawn every two years, whereas females spawn every 2-4 years. Adults migrate from the estuary into the river in winter, spawn from February to June, and return to the Delta after spawning. The early life of White Sturgeon in the wild is still not well understood and in need of continued research. Current evidence indicates that dispersed, fertilized eggs settle to the bottom and stick hard surfaces. Eggs hatch into the larval stage after about 12 days. The newly hatched larvae swim actively for several days before settling to the bottom. Juveniles move rapidly down-river in their first year, taking up residence in the freshwater region of the estuary. As adults, White Sturgeon move throughout the San Francisco Bay Estuary, occasionally making forays into coastal waters.
Threats
The primary spawning habitat of Sacramento-San Joaquin White Sturgeon is a short reach of middle Sacramento River, with some additional spawning occurring in the San Joaquin River, so the species is vulnerable to habitat loss and climate change that might degrade or destroy those areas. Other factors that threaten White Sturgeon include entrainment of early life stages into water diversions, contaminants from pollution and terrestrial runoff, and poaching and illegal fishing for meat and eggs.
Conservation and management
A historic commercial fishery for White Sturgeon existed in the late 1800's but was shut down in 1917 by the state of California after numbers declined precipitously. Once the population recovered, a recreational fishery for the species was permitted starting in 1954 and continuing to this day. The status of the fishery is monitored by CDFW using data from adult and juvenile surveys, and Sturgeon Fishing Report Cards. Currently, anglers with a report card can keep one fish per day, three fish per year, between 40-60 inches fork length. Anglers must use a single, barbless hook, may not use gaffs or snares, and must not remove any fish greater than 68 inches from the water. All fish captured must be reported on the Sturgeon Fishing Report Card. All sturgeon fishing is prohibited in the Sacramento River from the Highway 162 bridge to Keswick Dam.
Species status
White Sturgeon are not state or federally listed, but they are categorized as a state Species of Special Concern. Further details about the status of the species and the fishery can be found online in the CDFW White Sturgeon Enhanced Status Report. The American Fisheries Society considers the survival of sturgeon to be dependent on conservation measures taken to protect them.
Contact
For more information, please contact CDFW Fisheries Branch: Sturgeon@wildlife.ca.gov