Technical Report
Rio Grande Silvery Minnow Population Monitoring Program Results From December 2010 to October 2011
Date: 2012/04/06
Author(s): Dudley R.K., Platania S.P.
Publication: Prepared for U.S. Bureau of Reclamation, 146 p.
Abstract:
Population data on Rio Grande silvery minnow and the associated ichthyofaunal community in the Middle Rio Grande (Rio Grande between Velarde, New Mexico and Elephant Butte Reservoir) have been gathered systematically since 1993. The primary objective of the December 2010 to October 2011 sampling activities was to monitor temporal trends in the abundance of Rio Grande silvery minnow at twenty sites throughout the Middle Rio Grande. Additional objectives included evaluating the influence of discharge patterns on population fluctuations, determining general habitat use patterns, documenting changes in relative abundance among fish species over time, and determining site-specific sampling variation. Seasonal and spatial differences in population structure and abundance of native and nonnative Middle Rio Grande fishes were also examined.
Rio Grande silvery minnow October densities (1993-1997, 1999-2011) were significantly different among sampling years (df=17, F=17.5, p<0.0001) with the highest densities in 2005 and the lowest densities in 2003. October population monitoring efforts in 2011 demonstrated that Rio Grande silvery minnow density was significantly lower (p><0.05) than in recent years (e.g., 2007, 2008, and 2009) but not significantly higher (p>0.05) than in the lowest density years (e.g., 2002 and 2003). Also, October population monitoring samples illustrate that there was no significant change (p>0.05) in Rio Grande silvery minnow densities from 2010 to 2011.