|Scientific Name:||Acipenser fulvescens (Mississippi & Missouri Basins subpopulation)|
|Species Authority:||Rafinesque, 1817|
|Red List Category & Criteria:||Vulnerable A2acd ver 3.1|
|Assessor/s:||Runstrom, A. & St. Pierre, R. (U.S. Fish & Wildlife Service)|
|Reviewer/s:||St. Pierre, R. & Pourkazemi, M. (Sturgeon Red List Authority)|
Acipenser fulvescens was assessed by the IUCN SSC Sturgeon Specialist Group in 1996 as Vulnerable. A more detailed look at the data available for this species resulted in the global assessment being downgraded to Least Concern. However, the subpopulation in the Mississippi and Missouri River Basin area is still assessed as Vulnerable.
Although very little stock assessment work is underway, the lake sturgeon subpopulation in the Mississippi and lower Missouri river basins is believed to be stable but relatively small, certainly compared to levels in the late 1800s prior to development of modern locks, dams and reservoirs. Although extensive migrations have been reported, stocks are fragmented and spawning habitats are disrupted by development and adverse water quality. Except for a few, well regulated and short duration sport fisheries in select tributaries, harvest of lake sturgeon throughout this portion of their range is banned, but some illegal harvest has been reported.
Causes for decline of this subpopulation are known and, for the most part, irreversible. Area of occupancy, extent of occurrence and quality of habitats are all diminished compared to historic conditions. Restocking efforts using cultured fish are modest and fragmented among the states but results from Missouri DOC stockings are encouraging. Since there is currently no concerted basin-wide or interstate plan to manage or restore this stock lake sturgeon populations in the Mississippi river basin are considered to be Vulnerable.
|Range Description:||Lake sturgeon spend their entire life cycle in freshwater and are widely distributed in North America. They currently range throughout much of the drainages of the Mississippi River, the Great Lakes, Lake Champlain, the St. Lawrence River, Hudson Bay-James Bay, and the Saskatchewan River (Pflieger 1975, Becker 1983, Ferguson and Duckworth 1997). In the Mississippi basin this species occurs from the headwaters in Minnesota to the northern portion of the state of Louisiana and up the Missouri River into southern South Dakota. There is no known natural exchange of stocks between the Great Lakes and western Canadian provinces and those of the Mississippi River basin, though some stockings in the Mississippi have included lake sturgeon of Great Lakes Basin origin.|
Native:United States (Alabama - Regionally Extinct, Arkansas - Regionally Extinct, Iowa, Louisiana, Minnesota, Mississippi, Missouri, South Dakota, Wisconsin)
|Range Map:||Click here to open the map viewer and explore range.|
Lake sturgeon were generally considered to be rare to uncommon in most waters of the Mississippi River basin since the late 1800s. In 1989, this species was declared as threatened by the American Fisheries Society in all Mississippi River states except Louisiana where they are believed to be extirpated (Williams et al. 1989). The Department of Natural Resources in Iowa and Illinois and the Missouri Department of Conservation list the lake sturgeon as endangered in their respective states, and in Minnesota the lake sturgeon is listed as a species of special concern. The species appears to be extirpated from its former range in Alabama and Arkansas.
The current status of lake sturgeon throughout the Mississippi basin is considered to be severely depressed from historical abundance levels. However, modern population assessment studies are lacking and rate of stock decline or growth is unknown. Native stocks were extremely depressed prior to the stocking program undertaken by the Missouri Department of Conservation. Following the first releases into Mark Twain Lake (Salt River, a Pool 24 tributary) in 1984, then at Louisiana on Pool 24 of the Mississippi River and at several Missouri River locations in 1988, increasing reports of incidental catch in commercial gear and by recreational anglers has been occurring.
|Habitat and Ecology:||
Pectoral fin ray sections have been used to determine that lake sturgeon can live to be over 100 years old - though most are less than 35 years old. Lake sturgeon typically grow to almost two metres in length and about 90 kg, with rare records from the Great Lakes of fish up to 141 kg (Priegel and Wirth 1971). Compared to sturgeon from Lake Winnebago (Wisconsin) and the Great Lakes, relatively little information is available regarding age, growth, maturity and spawning periodicity of lake sturgeon in the Mississippi River basin.
Based on information from northern populations, lake sturgeon spawning occurs when water temperatures rise and reach 9–15°C (Priegel and Wirth 1971, Kempinger 1988). Spawning sturgeon will select shallow areas with relatively strong current velocities (Kempinger 1988).
Usual lake sturgeon habitat is the highly productive shoal areas of larger lakes, reservoirs and rivers. Lake sturgeon in the Upper Mississippi River prefer habitat in or adjacent to flow, but with relatively low to moderate current velocity (B.C. Knights, USGS, unpublished data). They are rarely found in backwater habitats without flow. In the Mississippi basin habitat that is in or adjacent to current is generally depositional and has relatively compact silt or silt-sand substrates with presumed high densities of benthic invertebrates. These areas occur at the lower end of navigation pools near the main channel, the mouths of tributaries and large secondary channels, and at some channel border areas. While migrating, presumably en-route to spawning habitats or high use (feeding/home) areas, lake sturgeon will use areas of the river with relatively high current velocities including tailwaters, the main channel in the upper and mid reaches of navigation pools, and tributaries.
Lake sturgeon are known to move great distances to spawning and feeding habitats (Auer 1996). In a recent study, nearly half of lake sturgeon radio-tagged in Pool 10 of the Mississippi River near Prairie du Chien, Wisconsin moved up the Wisconsin River about 140 km to the Prairie du Sac dam (Knights, B.C., USGS, unpublished data). Fish tagged in Pool 5A near Winona, Minnesota moved as far downstream as Pool 10 near Clayton, Iowa (about 170 km). Fifty-four occurrences of passage through navigation dams were observed and 46% of tagged sturgeon moved through at least one dam during the 18–month study. One lake sturgeon tagged in the Wisconsin River at Prairie du Sac, Wisconsin, traveled 415 km and moved through seven dams between September 28, 1999 and March 28, 2001, when it was recaptured by an angler at Lock and Dam 3 of the Mississippi River (A. Runstrom, USFWS, unpublished data). Lake sturgeon stocked by the Missouri Department of Conservation into Pool 24 of the Mississippi River and at several locations on the Missouri River have been reported as far upstream as the Lock and Dam 19 tailwater, as far downstream as Chester, IL, and as far up the Missouri River as the Gavins Point Dam tailwater (K. Brummett, MODOC, unpublished data).
The life history characteristics of slow growth, late maturation, and irregular spawning periodicity make lake sturgeon populations particularly vulnerable to over-exploitation. Sturgeon populations are threatened by industrial and municipal pollution, blockage of access to habitats by dikes and dams, channelization and elimination of backwater areas, dewatering and water level fluctuations, physical destruction of spawning habitat, and inundation of habitat by reservoirs (Rochard et al. 1990, Auer 1996, Beamesderfer and Farr 1997, Noakes et al. 1999).
Although there are numerous recorded instances of tagged sturgeon passing through navigation locks, many fish are precluded or delayed from reaching spawning or preferred feeding waters. Dams without locks completely block sturgeon passage and serve as severe impediments to lake sturgeon recovery in the Mississippi basin. Spawning and nursery areas are further degraded from land use problems such as erosion and sedimentation, and direct mortality of lake sturgeon due to impacts with commercial and/or recreational navigation vessels has been documented.
Although lake sturgeon harvest from the Mississippi River is prohibited, financial incentive to collect roe for caviar remains. Small population sizes may limit poachers from targeting this species but it is likely that incidental captures are utilized and end up in the black market. With the first stocking of lake sturgeon by Missouri DOC now at age 17, there is increasing concern that poachers will target them as the females reach maturity within the next few years.
Commercial harvest of lake sturgeon is prohibited in all U.S. waters. Sport fishing for lake sturgeon is currently prohibited in the Mississippi River but is allowed in some tributaries in Wisconsin and Minnesota (e.g., Wisconsin, Chippewa, and St. Croix rivers) during a short hook and line season in the fall. Angling in Minnesota has several restrictions as to season, fish sizes and gear and the reported annual sport catch was 2,200–4,200 kg in 1998–2000. Harvest is not allowed in Iowa, Ohio, Kansas, Missouri, Illinois and South Dakota.
Construction of spawning habitats using coarse stone rip-rapping has been undertaken in some states (particularly Wisconsin) and appears to be highly successful. To help restore populations several states are involved in culture and supplemental stocking programs. The largest of these is Missouri which has stocked over 210,000 lake sturgeon fingerlings in the upper Mississippi and lower Missouri rivers since 1986. Survival of stocked fish is considered excellent as tagged lake sturgeon have been recaptured in the Mississippi, Missouri, Gasconade and Osage rivers and commercial fishermen have reported incidental catches reaching nuisance proportions (Hesse and Carreiro 1997).
Artificial culture and restocking of lake sturgeon is also under development in Minnesota using wild broodstock. Wisconsin DNR propagates some lake sturgeon for restocking purposes with most cultured fish being placed into the same river basins from which broodstock were taken. The Tennessee Valley Authority has stocked thousands of young lake sturgeon within the Ohio River Basin.
|Citation:||Runstrom, A. & St. Pierre, R. (U.S. Fish & Wildlife Service) 2004. Acipenser fulvescens (Mississippi & Missouri Basins subpopulation). In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 23 May 2013.|
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