Technical Report

Rio Grande Silvery Minnow Population Estimation Program Results From October 2006

URL: https://webapps.usgs.gov/mrgescp/documents/Dudleyetal_2007_RGSMPopulationEstimationProgramResultsfromOctober2006.pdf

Date: 2007/12/19

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

Publication: Report prepared for U.S. Bureau of Reclamation, 84 p.

Abstract:

Systematic monitoring of Rio Grande silvery minnow, Hybognathus amarus, and the associated Middle Rio Grande fish community has been conducted since 1993. Throughout the past decade, the Rio Grande silvery minnow Population Monitoring Program has provided relevant, quantifiable, and timely information regarding the status of this species both spatially and temporally. Meeting the changing demands on this study program while attempting to fulfill the information needs of natural resource and water managers has been accomplished by increasing sampling frequency, increasing the number of sampling sites, or both. The proven ability of the Rio Grande silvery minnow Population Monitoring Program to provide timely and detailed information on all life stages of this species at both spatial and temporal scales underscores the strength and value of this study. Information gleaned from Rio Grande silvery minnow population monitoring samples is most useful when viewed collectively and in sequence.

Although the initial Rio Grande silvery minnow Population Monitoring Program was never designed to provide a population estimate of this species, performance of the aforementioned Program should not preclude concurrent investigations that provide an estimate of the number of Rio Grande silvery minnow. 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 number of 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 were presented within the context of those assumptions, especially given inherent variation in densities of organisms in the environment.