Technical Report

Rio Grande Silvery Minnow October Monitoring: 2020

URL: https://webapps.usgs.gov/mrgescp/documents/Best-and-Bullard_2022_2020-RGSM-Fall-Seining-Report.pdf

Date: 2022/08/01

Author(s): Best E., Bullard M.,

Publication: Prepared by Bureau of Reclamation, Technical Service Center, Denver, Colorado. Prepared for Bureau of Reclamation Albuquerque Area Office, 34 p.

Abstract:

In late October 2020, the Bureau of Reclamation (Reclamation) conducted surveys for the federally endangered Rio Grande silvery minnow (Hybognathus amarus) at select sites along the Rio Grande below the San Acacia Diversion Dam to the South Monticello boat ramp in Elephant Butte Reservoir. Reclamation and U.S. Fish and Wildlife Service biologists sampled 10 sites using seine nets. Surveys were conducted to maintain compliance with the Endangered Species Act requirements for Reclamation’s river maintenance and water management activities and to evaluate potential habitat restoration projects.

During the fall seining efforts, 17 Rio Grande silvery minnows were captured: 9 at the South Monticello site, 3 at the Upper Escondida site, 2 at the Lower Escondida site, 2 at the San Acacia site, and 1 at the Nogal Canyon site. The length-frequency histograms indicated that roughly half of the silvery minnows captured in 2020 were young-of-year, which suggests a lack of recruitment associated with the low flows that attributed to the lower numbers of age-0 silvery minnows observed in 2020, and it also informs us that there was some recruitment experienced.