Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

21.  ESTIMATES OF SHOVELNOSE STURGEON AND PALLID STURGEON POPULATION DENSITIES IN THE PLATTE RIVER, NEBRASKA, 2000-2004.

Edward J. Peters*, 12 Plant Industry Building, School of Natural Resources, University of Nebraska, Lincoln, NE 68583-0814; Phone 402-472-6824; FAX 402-472-2964; epeters2@unl.edu

James E. Parham, 311 Biochemistry Hall, School of Natural Resources, University of Nebraska, Lincoln, NE 68583-0758; Phone 402-472-2931; FAX 402-472-3601; jparham2@unl.edu

Jason  J. Olnes,  201 Natural Resources Hall, School of Natural Resources, University of Nebraska, Lincoln, NE 68583-0819; Phone 402-472-0825; FAX 402-472-2946; Jolnes@unl.edu

Dane A. Shuman, US Fish and Wildlife Service, PO Box 463, Pierre, SD 57501; Phone 605-224-8693; Dane_Shuman@fws.gov

Benjamin D. Swigle, US Geological Survey, 6935 Washburn Way, Klamath Falls, OR 97603; Phone 541-273-8689; bswigle@usgs.gov

Little is known about the population densities of Scaphirhynchus spp. that inhabit rivers in the central US and this limits the evaluation of management options for these fishes.  As part of a study to determine habitat use and movements of shovelnose sturgeon (Scaphirhynchus platorynchus) and pallid sturgeon (S. albus), we sampled fish using drifted gillnets and trammel nets during May-September 2000-2004 on the lower Platte River, Nebraska.  Catch per unit area was calculated for each net run. Area of suitable habitat was estimated using data from USGS gages and ongoing GIS analyses. Confidence limits were estimated using the rank 25th and 75th percentile catch values. A probability of capture coefficient was developed based on the frequency we captured radio-tagged fish when drifting nets over their known location. Over the four years of sampling, 1129 shovelnose sturgeon and 5 pallid sturgeon were captured in 323 gill net and 213 trammel net runs. After applying the probability of capture coefficient of 0.308, our median population estimate was 9.6 shovelnose sturgeon/ha with confidence limits from 9.2 to 27/ha.  The pallid sturgeon catch was 0.44% of the shovelnose sturgeon catch. Based on their relative abundance, we estimate that the pallid sturgeon population in the lower Platte River to be 0.042/ha with confidence limits from 0.040 to 0.12/ha.  We consider these to be survey level population estimates since the fish are from an open population with access to the Missouri River and sampling occurred over a variety of discharge levels, water conditions, and times when fish may have been concentrated for spawning activity or dispersed during migration.  Based on these density values, we estimate the lower Platte River’s shovelnose sturgeon population is between 23,000 and 69,000, and the pallid sturgeon population is between 103 and 303.