Nathan M. Kuntz | Geology Reports

USGS2014

Habitat use and selection by adult pallid sturgeon in the lower Mississippi River

The Pallid Sturgeon Scaphirhynchus albus is an endangered riverine sturgeon with historical distribution restricted to the Yellowstone, Missouri, Mississippi, and Atchafalaya rivers. Although not abundant, Pallid Sturgeon in the lower Mississippi River appear to be naturally recruiting, and information about habitat use is important to conserve this species. Thirty-four adult Pallid Sturgeon (612-1,013-mm FL) were tagged with acoustic transmitters and relocated a total of 272times in a 40-km reach of the lower Mississippi River from April 2009 through December 2012. Pallid Sturgeon strongly selected island tip and natural bank habitats, and, to a lesser degree, revetted bank habitat. Although frequently used, Pallid Sturgeon exhibited negative selection for the expansive main channel habitat. Secondary channel habitat was seasonally available and excluded from habitat selection analysis, but this habitat was frequently used in the spring when available. Fifty percent of Pallid Sturgeon detections were in relatively narrow ranges of depths (6.2-13.6m) and surface current velocities (0.64-1.05m/s). Use of different habitats was related to river stage and water temperature, suggesting use of some habitats was seasonal. Results suggest that maintaining natural bank habitat and secondary channel-island complexes will benefit conservation of this endangered species in the lower Mississippi River.

Arkansas↗

USGS2013

Observations on the identification of larval and juvenile Scaphirhynchus spp. in the lower Mississippi River

Scaphirhynchus albus (Pallid Sturgeon) and S. platorynchus (Shovelnose Sturgeon) are sympatric and not uncommon in the lower Mississippi River from the confluence of the Ohio River to the Gulf of Mexico, and in its distributary, the Atchafalaya River. Reports of sturgeon larvae have been rare in the Mississippi River but have been increasing with more effective collection methods. A suite of characters identified in hatchery-reared larval Pallid Sturgeon and Shovelnose Sturgeon from the Yellowstone and upper Missouri rivers has been used to distinguish larval Scaphirhynchus spp. In the Mississippi River; however, a large proportion of wild Scaphirhynchus spp. larvae are intermediate in these characters and have been identified by some as hybridized Pallid Sturgeon and Shovelnose Sturgeon. We applied three diagnostic characters developed from Missouri River sturgeon larvae to hatchery-reared progeny of Atchafalaya River Pallid Sturgeon and found them inadequate to identify most of the known Pallid sturgeon larvae. Additionally, fewer than 10% of a large sample of wild Scaphirhynchus spp. larvae from the lower Mississippi River conformed to either Pallid Sturgeon or Shovelnose Sturgeon at two or more of the characters. We also found a small mouth width relative to head width and a concave forward barbel position may be useful for the identification of 30% or more Scaphirhynchus spp. larvae and postlarval young-of-year as Shovelnose Sturgeon. Established adult character indices and diagnostic measurement proportionalities also failed to correctly identify any hatchery-reared Pallid Sturgeon juveniles recaptured 6–7 years following their release.

Southeastern Naturalist↗