| Abstract/Description or Keywords |
Species Information: The white sturgeon, Acipenser transmontanus, is the largest freshwater fish in Canada, sometimes exceeding 6 m in length. Sturgeon have rows of large bony plates, called scutes, along the back and sides. The scutes are quite sharp when the fish are young but gradually wear down as they age. Sturgeon skeletons are mostly cartilage instead of bone. They have no teeth but can extend their mouth to reach out and engulf food. The eggs hatch into larvae with an attached yolk sac, then metamorphose to look like miniature adults within 30 days. Green sturgeon, Acipenser medirostris, are sometimes found in the same rivers. These two species look similar and can be confused. White sturgeon have two rows of 4 - 8 scutes on the ventral surface between the pelvic and anal fins; green sturgeon have only one row of 1- 4 scutes. Green sturgeon are rarely seen in freshwater and are most often caught in salt-water commercial fisheries. Occasionally they are seen in the lower portions of larger coastal rivers in the late summer or early fall. Distribution: Spawning populations of white sturgeon are known to occur in three large river systems on the Pacific coast of North America (in the Fraser, Columbia and Sacramento drainages). In Canada, white sturgeon are found only in British Columbia: in the Fraser River system from the estuary upstream past the Morkill River, northwest of McBride; in the upper Columbia system in Arrow and Slocan lakes and in the mainstem downstream of Hugh L. Keenleyside Dam; and in the Kootenay River from Kootenay Lake upstream to the U.S. border. Reports of sturgeon from the Skeena, Nass and Yukon rivers, when checked, have been found to be green sturgeon. Habitat: Over the past century, white sturgeon habitat in British Columbia has declined in both quality and quantity. The diversion and regulation of water flows have likely had the most severe influence on sturgeon populations. Dams have heavily altered the flow regimes in the Columbia, Kootenay and Nechako systems. The possible effects of dams are wide ranging, including changes to water quality, streamflows, water temperature and habitat, as well as changes in species composition. The Fraser River mainstem is free running and has not been as heavily altered, but the amount of available sturgeon habitat on the lower river has declined since human settlement. Dredging, gravel extraction, dyking and channelization have been common practices. Contamination may also play a role in degrading habitat within and downstream from areas of high human use. Biology: The white sturgeon is a long-lived species. Some individuals in the Fraser River have been aged at over 100 years. Age of maturity varies with location and sex and can be anywhere from 14 years of age, for males in the lower Fraser River, to over 30 years for males in more northern areas. Although they typically survive spawning, it can be many years before they spawn again. Although often sedentary or localized in their movements, in some areas it is necessary for white sturgeon to move long distances between the various types of habitat necessary to complete their life history. They eat a variety of organisms from benthic invertebrates like crayfish, shrimp and clams to fish such as lamprey, salmon, and smelt. Population Sizes and Trends: Population declines have occurred throughout their Canadian range, particularly in the lower Fraser, Nechako, Columbia and Kootenay rivers. The abundance of sturgeon in the Fraser River mainstem upstream of Hell’s Gate may be naturally low but stable. Limiting Factors and Threats: White sturgeon are particularly vulnerable to overfishing due to their slow growth, late maturity and long life. The sturgeon commercial fishery that occurred prior to 1920 devastated sturgeon abundance in the lower mainland of British Columbia. Human activities also affect sturgeon populations through habitat change, particularly dam construction and flow regulation. Special Significance of the Species: The white sturgeon was once a valuable commercial species and is still highly valued for societal and cultural reasons, both recreationally and traditionally. Some First Nation’s peoples have harvested white sturgeon since long before Europeans arrived. The value of this large, ancient species as part of our natural heritage is tremendous, but cannot be estimated. Existing Protection or Other Status Designations: Throughout B.C., commercial and sport harvest has been prohibited since 1994 and some First Nations have voluntarily curtailed their fisheries. On the U.S. side, harvest is prohibited in the Kootenai River system (the same population is found in the Kootenay River and Kootenay Lake in B.C.) and upper Columbia rivers. The Kootenai River population was listed as endangered under the U.S. Endangered Species Act on September 6, 1994. The Kootenai White Sturgeon Recovery Plan, developed by U.S. Fish and Wildlife Service with input from Canadian agencies, is in the implementation phase. Recovery planning processes are under way for white sturgeon populations in the Nechako, upper Columbia and Fraser rivers. Recovery efforts for the transboundary white sturgeon populations in the upper Columbia and Kootenay rivers are closely coordinated with U.S. agencies. The recovery plan for the upper Columbia River white sturgeon is complete. Completion of the Nechako River white sturgeon recovery plan is targeted for 2004. Work on the Fraser River recovery planning process is in the preliminary stages. Recovery efforts have brought together: provincial and local governments; First Nations; experts in sturgeon biology, fish culture, recovery of endangered species, effects of hydroelectric dams, and habitat restoration; public and industrial stakeholders; and U.S. regulatory and tribal agencies for transboundary groups. In an attempt to compensate for failing recruitment, an experimental conservation culture facility has been established for the Kootenay (Kootenai) and Columbia sturgeon at Fort Steele, B.C. |
