By James H. Hale
The White Sturgeon (Acipenser transmontanus) is the largest freshwater fish in North America, with the maximum recorded length of any age class at 20 feet. The maximum published weight known is 1,799 pounds, with a reported age of 104 years. Those greater than 15 feet are suspected of reaching weights in excess of 3,000 pounds. I have canoed portions of the upper Sacramento River in my 18 foot long expedition canoe, with schools of and individuals approaching 15 feet passing underneath me. The hydraulics generated by these magnificent, prehistoric giants made it difficult to navigate. The White Sturgeon is an anadromous fish that ranges throughout the Eastern Pacific, from the Gulf of Alaska to Monterey Bay, California. Landlocked populations occur in Lake Shasta, Montana, and the Columbia River Drainage. Sightings of White Sturgeon have been reported in northern Baja California, Mexico.
Ancestors of the White Sturgeon originated around 45.8 million years ago. The Amur (Acipenser schrenckii), which is found only in Asia is a close genetic relative. The White Sturgeon is part of a Pacific clade or group of species with a common ancestor. These species include the Green Sturgeon (Acipenser medirostris), Sakhalin (Acipenser mikadoi), Chinese (Acipenser sinensis), Amur (Acipenser schrenckii), and Kaluga (Huso dauricus). The White Sturgeon is also commonly known as the Pacific Sturgeon, Sacramento Sturgeon, Oregon Sturgeon, Columbia Sturgeon, and Snake River Sturgeon. The specific name is derived from the Latin acipenser (sturgeon), trans (beyond), and montanus (mountain).
This is a unique fish. Instead of scales, it has five rows of bony plates called scutes that reach from its gills to its tail, covering its sandpaper like skin. The upper, dorsal color ranges from gray to brownish. The ventral, belly color is paler. The fins are gray. Similar to sharks, the White Sturgeon has a cartilaginous skeleton and a shark-like tail. Unlike most other fishes, its taste buds are located on the outside of its mouth. Barbels, which are feelers located under the sturgeon’s snout, help to locate potential food. A toothless, protrusible, siphon-like mouth sucks up the food once its located. Juveniles less than two feet in length, feed on amphipods (freshwater shrimp, scuds or sideswimmers), especially Corophium spp., mysids, isopods, benthic invertebrates, (which are community of organisms that live on, in, or near the seabed, also known as the benthic zone) as well as the eggs and fry of other fish species. Adults greater than two feet in length consume a variety of prey species as they adjust to a fish-eating, piscivorous diet. Starry flounder, herring, shad, goby, and benthic bivalves, such as clams, are common food items.
Studies suggest that they are nocturnal foragers in the estuaries of large rivers where they primarily live.
White Sturgeon are capable of spawning in multiple reproductive cycles over the course of their lifetime. As anadromous fish, they migrate upstream to freshwater to spawn. Their age at sexual maturity is uncertain, however, known ages range from 6 to 34 years old. Males are thought to spawn every 1-2 years, while females appear to spawn every 2-4 years. White Sturgeon spawn on gravel or rocky substrate, in moderate to fast currents, at depths ranging from 9-80 feet. Spawning behavior is not well known. The eggs sink when the female releases them during spawning. Upon contact with water, the eggs develop an adhesive coating which facilitates attachment to the substrate. They are communal broadcast spawners, where a female’s eggs are fertilized by many males. Females produce from 100,000 to 4 million eggs per spawning. The hatching time for eggs is temperature dependent, ranging from 3-13 days, with optimal temperature between 57-61 degrees. Once the larvae metamorphose into young of the year and juveniles, they actively feed on the substrate.
White Sturgeon are an important social and economic resource to many cultures around the world. In California, they are cultivated by aquaculture facilities, and juveniles can be legally sold to aquarists. In Contra Costa County, prehistoric Bay Miwok Saclan and Chupcan tribelets were proficient sturgeon fisherman for millennia. They would fish the Carquinez Straits from their tule-constructed canoes. Large amounts of White Sturgeon bones have been found in their village midden deposits. In the 1800’s, White Sturgeon were the main food source for the First Nations Peoples. By the early 1900’s, commercial fleets overfished the population for caviar to the point of near extinction.
In 1917, California banned commercial and sport fishing for White Sturgeon. White Sturgeon are used for meat, caviar, oil, and isinglass. Isinglass is a kind of gelatin obtained from the swim bladder, and used for making jellies, glue, and for clarifying ale. The selling of wild White Sturgeon and their eggs is illegal in California. However, legal caviar from California White Sturgeon farms may be purchased. Poaching is a serious problem. Black market caviar sells for 100-150 dollars a pound, while legally made California White Sturgeon farm caviar sells for 40-700 dollars an ounce. In California and the Pacific Northwest, White Sturgeon sport fishing is an important recreational activity. Historical ranges have been modified substantially due to over- harvesting, low river flows, and habit changes due to dams, pollutants, and river regulations, all of which affect habitat quality, suitability, and connectivity. NatureServe ranks White Sturgeon as imperiled in California due to impacts on their habitats.
James M. Hale is a Vertebrate Zoologist, Wildlife Biologist, Ethnobiologist, and Ecological Consultant based in Contra Costa County. Please visit his website at www.dochale.com