Pallid sturgeon


Pallid sturgeon

Taxobox
name = Pallid sturgeon
status = EN | status_system = IUCN3.1


image_width = 250px
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Acipenseriformes
familia = Acipenseridae
subfamilia = Scaphirhynchinae
genus = "Scaphirhynchus"
species = "S. albus "
binomial = "Scaphirhynchus albus "
binomial_authority = Forbes and Richardson, 1905
The pallid sturgeon ("Scaphirhynchus albus") is an endangered species of ray-finned fish endemic to the waters of the Missouri and lower Mississippi River basins of the United States. In 1990, the U.S. Fish and Wildlife Service placed the pallid sturgeon on the endangered species list because very few young pallid sturgeons were observed and overall sightings of the fish had greatly decreased in the preceding decade.cite web | last = | first = | authorlink = | coauthors = | year = | url = http://www.fws.gov/midwest/Endangered/section7/pallid.html | title = Section 7 Consultation on Operation and Maintenance of the Upper Mississippi River 9-Foot Channel Pallid Sturgeon | format = | work = Endangered Species | publisher = U.S. Fish and Wildlife Service | accessdate = 2008-07-04] The pallid sturgeon was the first fish species in the Mississippi River drainage that was listed as endangered. Current populations of the fish are small, and the fish is now rarely seen in the wild.

The pallid sturgeon is closely related to the relatively common Shovelnose sturgeon ("Scaphirhyncus platorhynchus"), however the pallid sturgeon is much larger, averaging between 30 and 60 inches (76 to 152 cm) in length and weighing 85 pounds (39 kg) at maturity.cite web | last = | first = | authorlink = | coauthors = | year = | url = http://fwp.mt.gov/wildthings/tande/pallid.html | title = Pallid Sturgeon - Scaphirhynchus albus | format = | work = | publisher = Montana Fish, Wildlife and Parks| accessdate = 2008-09-22] cite web| last = | first = | authorlink = | coauthors = | title = The Pallid Sturgeon (Scaphirhynchus albus) | work = | publisher = Platte River Endangered Species Partnership| date = | url = http://www.platteriver.org/backgr/sturg.htm| format = | doi = | accessdate = 2008-07-04] Evolving during the Cretaceous period 70 million years ago, they are a relic of the dinosaur era. Pallid sturgeon can live for 100 years and have been called the ugliest fish in North America.cite web | last = | first = | authorlink = | coauthors = | year = | url = http://www.r6.fws.gov/feature/sturgeon.html | title = The Pallid Sturgeon, a Missouri River "Dinosaur" | format = | work = Feature Series, Vol I, No. 4 | publisher = U.S. Fish and Wildlife Service| accessdate = 2008-07-04]

The pallid sturgeon is thought to have become endangered due to a loss of habitat. The vast majority of the Mississippi River drainage system has been channeled and dammed, reducing gravel deposits and slow moving side channels that are favored spawning areas. The fish was relatively common until the middle of the 20th Century, and anglers found landing such a large fish in fresh water a rewarding experience. The species is also considered to be an excellent tasting fish, and like many sturgeon, the eggs have been used as caviar, though this was never common with this species.cite web| last = | first = | authorlink = | coauthors = | title = Threatened and Endangered Species: Pallid Sturgeon Scaphirhynchus Fact Sheet | work = | publisher = U.S. Department of Agriculture| date = November 16, 2005| url = http://www.mt.nrcs.usda.gov/news/factsheets/pallidsturgeon.html| format = | doi = | accessdate = 2008-07-04]

Efforts to restore the species have yet to yield positive results. Capturing a young pallid sturgeon has become a rare event since the 1980s. With the major alterations to natural spawning areas that have occurred throughout their native habitat, restoration of these areas throughout the Mississippi River drainage basin will be mandatory if the species is to be expected to survive in the wild. Active efforts using fish hatcheries for spawning may help to ensure the species continues to exist, but this existence is heavily dependent on human assistance. In an effort to better understand pallid sturgeon behavior, researchers have implanted GPS transmitters, making it easier to track their movements and help identify possible spawning areas.

Taxonomy and etymology

The pallid sturgeon's closest relatives are the shovelnose sturgeon ("Scaphirhyncus platorhynchus"), which is still relatively common, and the critically endangered Alabama sturgeon ("Scaphirhynchus suttkusi"), which may now be extinct.cite news | last = | first = | coauthors = | title = Sturgeon lives, at least on list| work = | pages = | language = | publisher = The Birmingham News| date = January 14, 2008| url = http://www.al.com/opinion/birminghamnews/index.ssf?/base/opinion/1200302136306450.xml&coll=2| accessdate = 2008-07-04] Taxonomists S. A. Forbes and R.E. Richardson classified the pallid sturgeon in 1905, and along with the shovelnose, grouped them in the "Scaphirhynchus" genus and the "Acipenseridae" family, which includes all sturgeon worldwide. Pallid and shovelnose sturgeon can produce hybrid offspring, however DNA sequencing has determined that all three species of sturgeon in the "Scaphirhynchus" genus are distinct.cite journal| last = Campton| first = Donald E.| authorlink = | coauthors = Anna L. Bass, Frank A. Chapman and Brian W. Bowen| title = Genetic distinction of pallid, shovelnose, and Alabama sturgeon: emerging species and the US Endangered Species Act | journal = Conservation Genetics| volume = 1| issue = 1| pages = 17–32| publisher = Springer Netherlands| location = | month = March | year = 2000| url = http://www.springerlink.com/content/w76485t849537674/| doi = 10.1023/A:1010121417487| id = | accessdate =2008-07-04] Since the 1970s, the rates of hybridization between the pallid and shovelnose have increased and this is attributed to changes in the Mississippi and Missouri Rivers, forcing pallid sturgeons into areas where they have a greater chance of encountering shovelnose sturgeons.

Two populations of pallid sturgeon located in the upper Great Plains section of the Missouri River are considered to be genetically distinct from a third southern population located in the Atchafalaya River in Louisiana. The DNA showed that these populations have been reproductively isolated but are physically indistinguishable, aside from size, with the northern Missouri River individuals being much larger.cite web| last = | first = | authorlink = | coauthors = | title = Pallid Sturgeon (Scaphirhynchus albus) 5-Year Review Summary and Evaluation| work = | publisher = U.S. Fish and Wildlife Service| date = 2007| url = http://www.uwyo.edu/enr/ienr/PSWorkshop2007/Pallid_Sturgeon_5year_Review_Final_June2007.pdf| format = | doi = | accessdate = 2008-09-20] DNA sampling of shovelnose sturgeon taken from the same three locations showed that the shovelnose were genetically identical to each other. DNA from fish identified physiologically as hybrid pallid/shovelnose showed genetic distinction from pallid sturgeons yet were genetically identical to shovelnose.cite journal| last = Tranah| first = G. J.|authorlink = | coauthors = H. L. Kincaid, C. C. Krueger, D. E. Campton, and B. May| title = Reproductive isolation in sympatric populations of pallid and shovelnose sturgeon| journal = North American Journal of Fisheries Management| volume = 21| issue = | pages = 367-373| publisher = | location = | month = March | year = 2001| url = | doi = | id = | accessdate =2008-09-20] The southern populations had a larger number of reported hybrids than was found in the middle sections of the Missouri River basin, while the northernmost populations had few to no reports of hybrids.

The word "pallid" means "deficient in color",cite web| last = | first = | authorlink = | coauthors = | title = pallid| work = | publisher = Merriam-Webster| year = 2008| url = http://www.merriam-webster.com/dictionary/pallid| format = | doi = | accessdate = 2008-07-04] and compared to other species of sturgeon, the pallid is noticeably less colorful in appearance.cite web| last = | first = | authorlink = | coauthors = | title = Pallid Sturgeon| work = Animal Field Guide| publisher = Montana Fish, Wildlife and Parks| date = | url = http://fwp.mt.gov/fieldguide/detail_AFCAA02010.aspx| format = | doi = | accessdate = 2008-07-04] The scientific name for the fish is derived from "Scaphirhynchus", a Greek word meaning "spade snout" and "albus" which is Latin for the color white.cite web| last = Riis| first = Jim| authorlink = | coauthors = | title = Pallid Sturgeon (Scaphirhynchus albus)| work = | publisher = South Dakota Department of Game, Fish and Parks| year = 1993| url = http://www.northern.edu/natsource/ENDANG1/Pallid1.htm| format = | doi = | accessdate = 2008-07-04]

Biology

Physical characteristics

The pallid sturgeon is one of the largest freshwater fish species in North America. They are generally between 30 and 60 inches (76 to 152 cm) in length and weigh as much as 85 pounds (39 kg).cite web | last = | first = | authorlink = | coauthors = | year = | url = http://fwp.mt.gov/wildthings/tande/pallid.html | title = Pallid Sturgeon - Scaphirhynchus albus | format = | work = | publisher = Montana Fish, Wildlife and Parks| accessdate = 2008-09-22] cite web| last = | first = | authorlink = | coauthors = | title = The Pallid Sturgeon (Scaphirhynchus albus) | work = | publisher = Platte River Endangered Species Partnership| date = | url = http://www.platteriver.org/backgr/sturg.htm| format = | doi = | accessdate = 2008-07-04] The species is ancient and has remained virtually unchanged for 70 million years, since the Cretaceous period. As such, the pallid sturgeon has a distinctive appearance which has been referred to as "primitive", "dinosaur-like" and even "ugly". Though similar in appearance, the shovelnose sturgeon is much smaller and usually weighs no more than 5 pounds (2.25 kg). Pallid sturgeons are also much paler in coloration with grayish white backs and sides while shovelnose sturgeon are brown. Pallid sturgeons turn whiter as they age and younger specimens are easily confused with adult shovelnose sturgeon since they are similar in color.cite web| last = | first = | authorlink = | coauthors = | title = Endangered Sturgeon Struggle for Survival | work = The Sturgeon of Missouri Missouri's Aquatic Dinosaurs| publisher = Conservation Commission of Missouri| year = 2008| url = http://mdc.mo.gov/fish/sport/sturgeon/info/| format = | doi = | accessdate = 2008-07-04] They have a shark-like appearance as do many sturgeon species. Like the shovelnose sturgeon, their tails are heterocercal, with the top tail fin being longer than the bottom fin, though this is even more pronounced on pallid sturgeons.

Like other sturgeons, pallid sturgeons do not have scales or bones as are found in more modern species of fish. Instead, they have cartilaginous skeletons with 5 rows of thick cartilage plates that extend along their sides, undersides and backs, as well as most of the head. These thick cartilage plates are covered by the skin and serve as a protective armor.cite book| last = Johnsgard| first = Paul A.| authorlink = | coauthors = | title = The Nature of Nebraska| publisher = Bison Books| date = April 1, 2005| location = | pages = 169-170| url = | doi = | id = | isbn = 978-0803276215] The bony cartilage also extends along the backside, from the dorsal fin to the tail.

The pallid sturgeon snout and head are longer than that of the shovelnose sturgeon. in both species, the mouth is located well back from the tip of the snout. Lacking teeth they use their extendable mouths to suck up small fish, mollusks and other food sources from river bottoms. Both species also have four barbels which descend from the snout near the front of the mouth. The barbels are believed to be sensory features to locate food sources. On pallid sturgeons, the two inner barbels are only about half as long as the outer ones, while on the shovelnose sturgeon, all four barbels are the same length. The inner barbels of the pallid sturgeon are also positioned ahead of the outer ones, whereby those on the shovelnose sturgeon are all located in essentially a straight line. The length and positioning of the barbels is one of the best ways to distinguish the two species.

Reproduction and life cycle

Pallid sturgeon have very long lifespans but it is unclear exactly how long they live. A lack of bones and scales has made exact age determination difficult in those fish that have been researched.cite web| last = Holm | first = Rob| authorlink = | coauthors = | title = Prehistoric Presence The Pallid Sturgeon| work = | publisher = North Dakota Outdoors| date = April-May 2002| url = http://gf.nd.gov/multimedia/ndoutdoors/issues/2002/apr-may/docs/sturgeon.pdf| format = pdf| doi = | accessdate = 2008-07-04] It is generally believed that pallid sturgeons live in excess of 50 years and perhaps as long as 100 years.cite web| last = | first = | authorlink = | coauthors = | title = Upper Missouri Pallid Sturgeon| work = | publisher = National Wildlife Federation| date = | url = http://www.nwf.org/endangered/pdfs/UM-PallidSturgeon.pdf| format = pdf| doi = | accessdate =2008-07-04] cite web| last =Burton | first =Ken | authorlink = | coauthors = | title = New Hope for the Pallid Sturgeon| work = Endangered Species Bulletin| publisher = U.S. Fish and Wildlife Service| date = January/April 2000| url = http://www.fws.gov/endangered//bulletin/2000/01-04/04-05.pdf| format = pdf| doi = | accessdate =2008-07-04] cite web| last = | first = | authorlink = | coauthors = | title = Abnormal Cells found in Pallid Sturgeon at Gavins Point National Fish Hatchery Prohibit Stocking these Fish in the Wild| work = | publisher = U.S. Fish and Wildlife Service| date = September 26, 2007| url = http://www.fws.gov/mountain-prairie/PRESSREl/07-61.htm| format = | doi = | accessdate = 2008-09-28] As is true for many long lived species, pallid sturgeons take many years before they reach reproductive maturity.cite web| last = | first = | authorlink = | coauthors = | title = Status and Life History of the Pallid Sturgeon| work = | publisher = U.S. Environmental Protection Agency| date = August 31, 2007| url = http://www.epa.gov/espp/litstatus/effects/appendix_c_life_history_sturgeon.pdf| format = pdf| doi = | accessdate = 2008-07-04] Male pallid sturgeons reach sexual maturity between the ages of 5 and 7 years, while females are believed to not become capable of reproduction until they are at least they 15 years old. In one study research on 9 females indicated that they begin egg development between the ages of 9 and 12 years, but do not reach reproductive maturity until they are 15 years old. Reproduction is not known to occur every year and and spawnings averaged intervals of three years.cite journal| last = Keenlyne| first = K.D.| authorlink = | coauthors = L.G. Jenkins| title = Age at Sexual Maturity of the Pallid Sturgeon| journal = American Fisheries Society| volume = 122| issue = 3| pages = 393–396| publisher = American Fisheries Society| location = | month = May | year = 1993| url = http://afs.allenpress.com/perlserv/?request=get-abstract&doi=10.1577%2F1548-8659(1993)122%3C0393:AASMOT%3E2.3.CO%3B2| doi = | id = | accessdate = 2008-07-04] Other research indicates that spawnings may be as much as 10 years apart.cite web| last = | first = | authorlink = | coauthors = | title = Pallid Sturgeon: The Road to Recovery| work = | publisher = U.S. Fish and Wildlife Service| date = July 15, 2008| url = http://www.fws.gov/YellowstoneRiverCoordinator/pallidsturgeon.html| format = | doi = | accessdate = 2008-10-04]

Prior to the construction of dams on the Missouri, pallid sturgeon would migrate hundreds of miles upstream to spawn.cite web| last =McKean | first = Andrew | authorlink = | coauthors = | title = A Whisker Away from Winking Out| work = | publisher = Montana Outdoors | date = May/June 2006| url = http://fwp.mt.gov/mtoutdoors/HTML/articles/2006/pallidsturgeon.htm| format = | doi = | accessdate = 2008-07-04] Usually spawning between the months of May and July, they would seek out rocky or hard surfaces and deposit hundreds of thousands of eggs.cite journal| last = Kallemeyn | first = Larry| authorlink = | coauthors = | title = Status of the Pallid Sturgeon "Scaphirhynchus albus"| journal = Fisheries| volume = 8| issue = | pages = 3–9| publisher = American Fisheries Society| location = | year = 1983| url = http://afs.allenpress.com/perlserv/?request=get-pdf&doi=10.1577%2F1548-8446%281983%29008%3C0003%3ASOTPS%3E2.0.CO%3B2| doi = | id = | accessdate = 2008-07-04| format = subscription required] One female pallid sturgeon that was caught in the upper Missouri River was estimated to be carrying 170,000 eggs, representing over 11 percent of its total body weight.cite journal| last = Keenlyne| first = K.D.| authorlink = | coauthors = E. M. Grossman and L.G. Jenkins| title = Fecundity of the Pallid Sturgeon| journal = American Fisheries Society| volume = 121| issue = 1| pages = 139–140| publisher = American Fisheries Society| location = | month = January | year = 1992| url = http://afs.allenpress.com/perlserv/?request=get-abstract&doi=10.1577%2F1548-8659(1992)121%3C0139%3AFOTPS%3E2.3.CO%3B2&ct=1| doi =| id = | accessdate = 2008-07-04] After fertilization, pallid sturgeon eggs hatch in 5 to 8 days. After spawning, the larvae would drift back downstream for several weeks and as the larvae developed tails they would seek out slower moving waterways and slowly mature over a period of a dozen years. The rates of survival to maturity for pallid sturgeons is extremely low and of the hundreds of thousands of eggs spawned, only a small handful live to adulthood.

For several decades, no natural reproduction of pallid sturgeons had been observed, since all the pallid sturgeons that had been captured were older specimens. However, in the late 1990s, young pallid sturgeons were discovered living in a restored riparian area of the lower Missouri River. This was the first documented example of wild spawned pallid sturgeons in 50 years. In 2007, two female pallid sturgeons were reported to have spawned in the Missouri National Recreational River area located downstream from Gavins Point Dam on the Missouri River.cite web| last = | first = | authorlink = | coauthors = | title = Sturgeon Research Update: Confirmed Pallid sturgeon Sturgeon Spawning in the Missouri River in 2007| work = | publisher = U.S. Geological Survey| month = July | year = 2007| url = http://pubs.usgs.gov/fs/2007/3053/pdf/FS2007-3053.pdf| format = pdf| doi = | accessdate =2008-07-04]

Ecology

Distribution

The pallid sturgeon's historical range spanned the entire Missouri and into the Mississippi Rivers, however the species is considered critically imperiled throughout its entire range.cite web| last = | first = | authorlink = | coauthors = | title = Scaphirhynchus albus - (Forbes and Richardson, 1905) | work = | publisher = NatureServe| month = | year = | url = http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Scaphirhynchus+albus| format = | doi = | accessdate =2008-09-20] The species was historically rare to nonexistent in the upper Mississippi, probably due to a lack of proper habitat. As of 2008, pallid sturgeons can still be found throughout their original range, but their population numbers have been severely reduced from what they were in the mid 20th century. The Missouri and Mississippi Rivers from Montana to Louisiana as well as the Atchafalaya River in Louisiana continue to have an aging population of pallid sturgeons. Pallid sturgeons have never been very common, and even as early as 1905 when the species was first identified, they represented only 1 in 5 of all sturgeon in the lower Missouri River and as few as 1 in 500 where the Illinois River meets the Mississippi.cite web| last = Grady| first = Joanne| authorlink = | coauthors = Jim Milligan| title = Pallid and Shovelnose Sturgeon in the Lower Missouri and Middle Mississippi Rivers| work = | publisher = U.S. Fish and Wildlife Service| month = February | year = 2001| url = http://www.fws.gov/midwest/columbiafisheries/documents/MICRA_sturgeon_report.pdf| format = pdf| doi = | accessdate = 2008-07-04] Between 1985 and 2000, the ratio of pallid sturgeons to all sturgeon netted declined from 1 in about 400 to 1 in nearly 650. A 1996 study concluded that between 6,000 and 21,000 pallid sturgeons remained in their natural habitat at that time.cite web| last =| first = | authorlink = | coauthors = | title = Scaphirhynchus albus | work = The IUCN Red List of Threatened Species| publisher = International Union for Conservation of Nature and Natural Resources| year = 2004| url = http://www.iucnredlist.org/search/details.php/19940/all| format = | doi = | accessdate = 2008-07-04]

Six areas were studied for wild pallid sturgeon population estimates and recovery recommendations by the United States Fish and Wildlife Service (USFWS) between 1990, when the species was declared endangered, and 2006. The USFWS has referred to these six areas of wild pallid sturgeon population studies as Recovery Priority Management Areas (RPMA's). In the northernmost region of the study, known as RPMA 1, located between the Marias River in Montana to the western reaches of Fort Peck Reservoir, only 45 wild (non-hatchery) individuals remain. Of these, no juveniles were observed and the population was declining. In RPMA 2, located between Fort Peck Dam, the headwaters of Lake Sakakawea and the lower Yellowstone River up to the confluence of the Tongue River, Montana, only 136 wild specimens remain. In RPMA 3, stretching from upstream of the Niobrara River to Lewis and Clark Lake along the Missouri River, no native populations were recorded. All collected specimens were apparently hatchery raised. However, the hatchery raised specimens were apparently maturing and adjusting well to this section of the river. RPMA 4 extends from Gavins Point Dam to the confluence of the Missouri and Mississippi Rivers. This region also includes the Platte River. Here, at least 100 unique non-hatchery specimens were collected during the study period. There is also evidence that some wild reproduction is ongoing in this region. In RPMA 5, between the confluence of the Missouri and Mississippi and the Gulf of Mexico, several hundred specimens were documented. Here again, some evidence suggests that natural reproduction is occurring, as demonstrated by the recovery of a few examples of immature, non-hatchery raised individuals. The Atchafalaya River basin is designated as RPMA 6 and the findings there were similar to those in Recovery Priority Management Areas 4 and 5 but with greater numbers of unique individuals, near 500 in total.

Habitat

Pallid sturgeons prefer moderate to swift river currents and most captured specimens have been recovered in rivers and streams in which the current averages between 0.33 to 2.9 feet (10 and 90 centimeters) per second. They also prefer turbid waterways and water depths between 3 and 25 feet (1 and 8 m). The species is more commonly found where sandy substrates are plentiful but can also be found in waterways that are predominately rocky. Pallid sturgeons tend to prefer swift river currents more often than do shovelnose sturgeon. In a Montana and North Dakota based study conducted on both the pallid and shovelnose sturgeon, both species were fitted with radio transmitters. Pallid sturgeons were found to prefer wider river channels, mid-channel sandbars and numerous islands and were most commonly recorded in water depths between 2 and 47 feet (.6 and 14.5 m). The study also showed that both pallid sturgeon moved up as much as mi to km|13 a day and up to mi to km|5.7 per hour.cite journal| last = Bramblett| first = Robert| authorlink = | coauthors = Robert White| title = Habitat Use and Movements of Pallid and Shovelnose Sturgeon in the Yellowstone and Missouri Rivers in Montana and North Dakota| journal = Transactions of the American Fisheries Society | volume = 130| issue = 6| pages = 1006–1025| publisher = American Fisheries Society| location = | year = 2001| url = | doi = | id = | accessdate =2008-07-04] Pallid sturgeon are believed to have always preferred muddy and generally warmer waters that existed prior to Missouri River dam construction.

Food preferences

Pallid sturgeons are generally bottom feeders, skimming the sandy reaches of the various rivers and streams in their habitat. Though little is known about the precise eating habits of the species, they are thought to be opportunistic feeders. One study which examined the contents from the stomachs of juvenile pallid sturgeons revealed that their diets were seasonally dependent. Various insects were consumed during some seasons and other fish species during others. The results indicated that pallid sturgeons are opportunistic in their eating habits.cite journal| last =Wanner | first = Greg| authorlink = | coauthors = D. A. Shuman, and D. W. Willis| title = Food Habits of Juvenile Pallid Sturgeon and Adult Shovel nose Sturgeon in the Missouri River Downstream of Fort Randall Dam, South Dakota| journal = Journal of Freshwater Ecology| volume = 22| issue = 1| pages = 81–92| publisher = | location = | month = March | year = 2007| url = http://wfs.sdstate.edu/wfsdept/Publications/Willis/439-F%20Pallid%20Shovelnose%20Sturgeon%20Wanner.pdf| doi = | id = | accessdate = 2008-07-04|format=PDF] Fish is a more important dietary staple for pallid sturgeon than it is for shovelnose sturgeon.cite web| last = | first = | authorlink = | coauthors = | title = Pallid Sturgeon | work = | publisher = The Iowa Department of Natural Resources| month = | year = | url = http://www.iowadnr.com/fish/iafish/pallstur.html| format = | doi = | accessdate =2008-09-28]

Conservation

Though never believed to be common, pallid sturgeon populations nosedived during the late 20th century and the species was listed as endangered on September 6, 1990. The U.S. Government and most of the states that have pallid sturgeon have commenced restoration efforts to save the species from extinction. Wild reproduction of pallid sturgeon is rare to nonexistent in most areas. Therefore, human intervention is needed to ensure the survival of the species.cite web | last = Wildhaber| first =Mark L. | authorlink = | coauthors = Aaron J. DeLonay, Diana M. Papoulias, David L. Galat, Robert B. Jacobson, Darin G. Simpkins, Patrick J. Braaten, Carl E. Korschgen, and Michael J. Mac| year = 2007| url = http://www.uwyo.edu/enr/ienr/PSWorkshop2007/circ_1315.pdf| title = A Conceptual Life-History Model for Pallid and Shovelnose Sturgeon | format = pdf| work = | publisher = USGS| accessdate = 2008-09-20] Pallid sturgeon were previously considered a prized trophy game fish species, until their numbers declined and they were placed on the endangered species list. All captured pallid sturgeon must now be released back to the wild. The species was known as being very palatable and the roe from females was used as caviar. Though substantial efforts are being implemented to ensure the survival of this species, the lack of self sustaining populations of pallid sturgeons ensures that it will remain federally protected for many decades.

The Missouri River in the northern Great Plains states of North Dakota and South Dakota, Nebraska and Montana, has been significantly altered. The resultant changes to the Missouri River in the upper Great Plains from channelization and impoundment prevent upstream migration, have reduced water flow rates and sediment loads and has brought an end to the seasonal flooding of the flood plains in the region. Since the construction of the Fort Peck Dam in Montana in 1937 and subsequent damming and channelization, the Missouri river has lost over 90 percent of its wetland and sandbar ecosystems. More than 2,000 miles (3,220 km) of the Missouri River has been altered and only that stretch of the river above Fort Peck Reservoir in Montana remains relatively unchanged.cite web | last = Power| first = Greg | authorlink = | coauthors = | year = 2006| url = http://www.npwrc.usgs.gov/resource/fish/othrfish/overview.htm| title = The Missouri River System's "Other" Fish | format = | work = | publisher = USGS| accessdate = 2008-09-20] These river alterations have had a detrimental impact on a number of native fish species, especially the pallid sturgeon, which was once relatively common in the region. However, pallid sturgeons are one of the only federally listed endangered fish species in the Missouri and Mississippi River systems. In the 13 U.S. states that the pallid sturgeon is found only a few other fish species are listed as endangered.cite web | last = | first = | authorlink = | coauthors = | year = 2008| url = http://ecos.fws.gov/tess_public/StateListing.do?state=all| title = How many species are listed in each state (based on published population data)? | format = | work =Threatened & Endangered Species System | publisher = U.S. Fish and Wildlife Service| accessdate = 2008-09-22] Two populations of pallid sturgeons in the Missouri and Yellowstone Rivers of Montana are both at risk of extinction and current projections are that wild pallid sturgeon populations in Montana will be extinct by 2018. Though a vigorous stocking effort was implemented in 1996, until pallid sturgeon females reach reproductive maturity sometime after they are 15 years of age, recovery efforts in Montana will not be readily measurable. The U.S. Bureau of Reclamation has been doing spring pulse water releases from the Tiber dam every 4 to 5 years to try and recreate some semblance of an annual spring flood to restore and rejuvenate downstream floodplains. The pulse releases are done in an effort to restore suitable habitat for numerous fish species.cite web | last = | first = | authorlink = | coauthors = | year = | url = http://fieldguide.mt.gov/detail_AFCAA02010.aspx| title = Pallid Sturgeon — Scaphirhynchus albus| format = | work = | publisher = Montana Field Guide| accessdate = 2008-09-22] In Nebraska a small number of pallid sturgeons have been captured along the lower reaches of the Platte River. Unlike most rivers in the Mississippi-Missouri river system, the Platte River has but a few dams and they are well upstream from its confluence with the Missouri River. The lower Platte River is shallow with numerous sand bars and small islands. Though pallid sturgeons prefer more turbulent and deeper rivers than the Platte River, between 1979 and 2003 over a dozen pallid sturgeons, including some from hatcheries, have been captured from the Platte River.cite book| last = Committee on Endangered and Threatened Species in the Platte River Basin| first = | authorlink = | coauthors = | title = Endangered and Threatened Species of the Platte River| publisher = The National Academies Press| year = 2004| location = Washington, D. C.| pages = 225-239| url = http://books.nap.edu/openbook.php?record_id=10978&page=225| doi = | id = | isbn = 978-0-309-09230-2] A number of these pallid sturgeons have been fitted with radio transmitters which indicate that they return to the Platte River when water levels and turbidity conditions are favorable. Coinciding with the majority of the pallid sturgeons that have been captured, this favorable period is generally during the spring and early summer months. By mid-summer, a reduction in water levels and turbidity on the Platte River encourages pallid sturgeons to return to the Missouri River. The lower reaches of the Platte River, a more than 30 mile (48 km) stretch from the Elkhorn River to its confluence with the Missouri River, has suitable spawning habitat for pallid sturgeons, though no conclusive evidence has been found that spawning is occurring in this region. Along with the lower Yellowstone River, the lower Platte River was identified as one of the best remaining regions for potential natural spawning to be possible. In an effort to help restore habitat, two large river water pulse releases are planned for the months of March and May 2009 from Gavins Point Dam, located on the border of Nebraska and South Dakota. The amount of water released from the dam is dependant on upstream reservoir levels and downstream river levels and will be regulated to ensure that downstream flooding will not occur, but there will be some restoration of the "historic ebb and flow of the river (which will) benefit the spawning of the pallid sturgeon".cite news | last = Hendee| first = David| coauthors = | title = Missouri River plan calls for '09 water pulses| work = | pages = | language = | publisher = Omaha World Herald| date = October 3, 2009| url = | accessdate = 2008-10-04]

In Missouri, at the Lisbon Bottoms section of the Big Muddy National Fish & Wildlife Refuge, wild pallid sturgeon larvae were collected in 1998. These non-hatchery raised larvae were the first recovered on the lower Missouri River in the previous 50 years. The recovery was made along a side channel of the Missouri River that had been developed to provide suitable habitat for pallid sturgeon and other fish spawning.cite news | last = Ikenson| first = Ben| coauthors = | title = Biologists struggle to keep the pallid sturgeon from going extinct | work = Reviving the Missouri River's dinosaur| pages = | language = | publisher = ESPN| date = May 31, 2006| url = http://sports.espn.go.com/outdoors/general/columns/story?columnist=guest_columnist&page=c_col_Ikenson_sturgeon_pallid| accessdate = 2008-07-04] The side channel was apparently being used by the larva pallid sturgeons for protection from the swifter currents of the Missouri River.cite web | last = Mississippi Interstate Cooperative Resource Association | first = | authorlink = | coauthors = | year = | url = http://wwwaux.cerc.cr.usgs.gov/MICRA/PALLIDST.HTM | title = Pallid Sturgeon, Scaphirhynchus albus | format = | work = | publisher = | accessdate = 2008-07-04]

The U.S. Fish and Wildlife Service concluded in 2007 that continued hatchery based reproduction efforts should be continued and that monitoring of any population changes must continue in order to determine the effectiveness of human intervention. The 2007 findings also emphasized the need to determine the most likely areas of spawning, to identify any parasitic or disease that may be impacting the reproductive capabilities of pallid sturgeon and to examine engineering possibilities that may permit recreation of suitable habitats without reducing the ability to protect people from harmful and destructive flooding, and maintaining the ability to provide adequate water impoundment for irrigation and recreation purposes. Close monitoring of hatchery raised pallid sturgeon in 2007 resulted in the discovery of some abnormal cell development, and these fish had to be destroyed before they were released. However, in the same year, the U.S. Fish and Wildlife Service released over 400,000 hatchery raised pallid sturgeon at various locations on the Missouri and lower Yellowstone Rivers.

Cited references

External links

* [http://www.fws.gov/YellowstoneRiverCoordinator/pallid%20recovery%20plan.pdf Pallid Sturgeon Recovery Plan (10mb file)]


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