Technical Report

Middle Rio Grande Nursery Habitat Monitoring - 2008

URL: https://webapps.usgs.gov/mrgescp/documents/Hatch%20and%20Gonzales_2008_Middle%20Rio%20Grande%20Nursey%20Habitat%20Monitoring%20-%202008.pdf

Date: 2008/12/31

Author(s): Hatch M.D., Gonzales E.

Publication: Report prepared for the U.S. Bureau of Reclamation, 25 p.

Abstract:

Surveys were conducted to reveal limiting factors that may underlie Rio Grande silvery minnow (Hybognathus amarus; silvery minnow) populations. We present an ecological characterization of fish species assemblages that include silvery minnow and that occur in isolated habitats lateral to running water in the main channel of the Middle Rio Grande. Some of these habitats conceivably represent nursery habitats for developing stages of young-of-year fish, although under circumstances of hydrologic scarcity, these habitats may also represent refugia for fish to escape mortality linked to diminishing surface water habitats. We offer a provisional description of how the faunal assemblages are structured by underlying physical and chemical features of their environment. Dispersal, environmental and biotic factors are presented as principal determinants of silvery minnow habitat occupancy. This description provides a context within which environmental, ecological, and other factors can be weighed against one another in formulating management goals, monitoring restoration progress, and measuring recovery of rare taxa.

Advancing pathways of ecological succession in the Middle Rio Grande result in increased fish species diversity with distance downstream. The number of fish reproductive guilds also increases with distance downstream, indicating the existence of a greater diversity of available ecological niches. We speculate that the rapid downstream increase in the number of reproductive guilds supported over the relatively short geographic distance spanned by the Albuquerque and Isleta reaches is attributable, in large part, to the natural restoration of successional stages of the river continuum that is disrupted upstream by the storage of water in Cochiti Reservoir.