Tuesday, May 7, 2013

Pallid Sturgeon Draft Recovery Plan Available

The U.S. Fish and Wildlife Service has released a draft revised recovery plan for the endangered Pallid Sturgeon Scaphirhynchus albus (http://ecos.fws.gov/docs/recovery_plan/Pallid%20Sturgeon%20Draft%20Revised%20Recovery%20final%20draft%2003%2004%202013%20for%20web%20publication.pdf). The species was listed as endangered in 1990, with the original recovery plan finalized in 1993. The Pallid Sturgeon is native to the Missouri and Mississippi rivers where it is restricted to the mainstem and lower reaches of larger tributaries.

The Pallid Sturgeon Scaphirhynchus albus. Illustration by Joe Tomelleri.
This species is adapted to the pre-development conditions of free-flowing turbid warm water rivers with a variety of physical habitats that were in a constant state of change. Pallid Sturgeon reach 5.5 feet and 90 pounds and can live up to 41 years, with largest and oldest individuals being found in the upper Missouri River and smaller sizes in the lower Mississippi River. Males are not sexually mature until age 5 or later and females may not reproduce until age 15-20 years. They migrate upstream in the winter, spawning in the spring on hard surfaces with flowing water. Females can produce up to 170,000 eggs, but an individual female only spawns every 3-10 years; males spawn every 2-3 years. Upon hatching, larvae are photopositive (attracted to light) and drift in the water column for 11-17 days and 152-329 miles. Reservoirs below spawning grounds can result in total recruitment failure likely due to larvae settling to the bottom and dying. Pallid Sturgeon cruise along the river bottom to locate and eat invertebrates and small fishes with the aid of taste buds on their barbels and ampullary organs on the underside of their head, which use electroreception to detect the weak electrical fields emitted by prey.

Two adult Pallid Sturgeon from different parts of their range, the larger specimen is from the upper Missouri River and the smaller southern specimen is from the lower Mississippi/Atchafalaya Rivers. Photo by Bernie Kuhajda.

Current limiting factors for Pallid Sturgeon include (1) activities that affect connectivity and the natural form, function, and hydrologic processes of rivers; (2) illegal harvest, especially females for their eggs for caviar production; (3) impaired water quality and quantity; (4) entrainment in water diversion structures such as flood gates; and (5) life history attributes of the species (delayed sexual maturity, females not spawning every year, and larval drift requirements). The degree to which these factors affect the species varies among river reaches. The draft revised recovery plan focuses on a number of key issues: 
  • The need to better understand certain life history traits and the complex interactions between these traits and altered habitats in the contemporary Missouri and Mississippi River basins.
  • Threats abatement
    • The listing of the Shovelnose Sturgeon (S. platorynchus) as threatened due to similarity of appearance within the range of the Pallid Sturgeon should decrease illegal harvest by eliminating caviar harvest.
  • Population management using augmentation to conserve extant genetic variability and prevent localized extirpation.
  • Researching and implementing habitat improvement.
  • Monitoring habitat conditions.
  • Monitoring population status.

Map of current range of Pallid Sturgeon, both wild and hatchery-reared fish. Data by National Pallid Sturgeon Database, U.S. Fish and Wildlife Service, Bismarck, North Dakota. Figure from the draft revised recovery plan.

USFWS requests your assistance by reviewing the draft revised recovery plan and providing any information that you may have on the Pallid Sturgeon that is not already included.  Information must be submitted on or before 14 May 2013 and can be submitted to the Project Leader, Northern Rockies Fish and Wildlife Conservation Office, U.S. Fish and Wildlife Service, 2900 4th Avenue North, Room 301, Billings, MT 59101.

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