Technical Report

Habitat Assessment for Rio Grande Silvery Minnow (Hybognatus amarus) in the Cochiti Reach, at Pena Blanca, New Mexico

URL: https://webapps.usgs.gov/mrgescp/documents/Torres_2008_Habitat%20Assessment%20for%20RGSM%20%28Hybognathus%20amarus%29%20in%20the%20Cochiti%20Reach%2C%20at%20Pena%20Blanca%2C%20NM.pdf

Date: 2008/04/17

Author(s): Torres L.T., Remshardt W.J., Kitcheyan D.C.

Publication: Report prepared for U.S. Army Corps of Engineers, 38 p.

Abstract:

A small-scale habitat assessment for Rio Grande silvery minnow (RGSM) was conducted in the Cochiti Reach at Peña Blanca, New Mexico to characterize habitat, document the status of RGSM, and provide recommendations regarding future management. Surveys were conducted during fall (November 2006), winter (February 2007), and spring (April 2007). Habitat characterization included transect and fish community data analysis from Peña Blanca, a hydrograph exceedence probability comparison of three U.S. Geological Survey (USGS) gauges (from 1975-2006), and a Geographical Information System (GIS) analysis of active channel changes (from 1992 and 2006) within the Cochiti Reach.

Channel morphology, velocities, and substrate were similar between Peña Blanca and previously surveyed sites above Cochiti Lake. Runs and pools were the most common mesohabitat type available at the Peña Blanca site. Substrate was sand and gravel. Velocities at Peña Blanca ranged from 0.0 to 5.5 ft/sec. Mean velocity was 2.25 ft/sec (± 0.04 SE). Cochiti Reach had higher average discharge than Isleta and San Acacia reaches, and less hydrographic diversity. No RGSM were collected and the site was primarily dominated by non-native fish species. Fish communities were different between Peña Blanca and downstream sites (Isleta and San Acacia reaches). Downstream sites displayed higher occurrences of slackwater areas, mesohabitats more often utilized by RGSM. Active channel GIS analysis indicated a continued trend in channel narrowing and incision within Cochiti Reach.