Technical Report

Rio Grande Silvery Minnow Population Estimation Program Results From October 2007

URL: https://webapps.usgs.gov/mrgescp/documents/Dudleyetal_RGSMPopulationEstimationProgramResultsfromOctober2007.pdf

Date: 2008/08/08

Author(s): Dudley R.K., White G.C., Platania S.P., Helfrich D.A.

Publication: Final report prepared for U.S. Bureau of Reclamation, 88 p.

Abstract:

Systematic monitoring of Rio Grande silvery minnow, Hybognathus amarus, and the associated Middle Rio Grande fish community has been conducted since 1993 and has provided relevant, quantifiable, and timely information regarding the status of this species both spatially and temporally. In contrast to the Population Monitoring Program, which continues to provide necessary year-round documentation of trends for the entire ichthyofaunal community, the Population Estimation Program provides a rigorous yearly estimate of the Rio Grande silvery minnow population during a single time-period (October). Estimating population size required employing statistical techniques that were subject to a series of assumptions. Estimates of the number of Rio Grande silvery minnow are presented within the context of those assumptions, especially given the inherent variation in the density and distribution of organisms within their environment.

Data collected during the 2007 Population Estimation Program indicated that the ichthyofaunal community in the Middle Rio Grande between Angostura Diversion Dam and Elephant Butte Reservoir was numerically dominated by cyprinids and included eight native fish species. Red shiner was the most abundant native species collected (N = 18,826), followed by Rio Grande silvery minnow (N = 3,122), flathead chub (N = 852), and river carpsucker (N = 429). The highest densities of Rio Grande silvery minnow were recorded in the Angostura and Isleta reaches.