Technical Report
Spatial Spawning Periodicity of Rio Grande Silvery Minnow During 2007
Date: 2007/12/01
Author(s): Platania S.P., Dudley R.K.
Publication: Report prepared for Middle Rio Grande Endangered Species Collaborative Program, 34 p.
Abstract:
Systematic monitoring of the reproductive output of Rio Grande silvery minnow at several sites in the Middle Rio Grande was first conducted in 1999 (Platania and Dudley, 2002) and has continued annually (except 2005) since 2001. Previous studies (Platania and Dudley 2002, 2003, 2004, 2005, 2006) demonstrated May and June as the primary period of silvery minnow reproductive activity. The 2006-2007 studies were structured to monitor the spatial and temporal (May-June) reproductive output of Rio Grande silvery minnow in the Middle Rio Grande and therefore, given the downstream drift of the eggs, were conducted near the downstream-most portion of each of the three accessible river reaches (Angostura, Isleta, and San Acacia).
There was a large difference in flow in the Middle Rio Grande in 2007 as compared to 2001- 2004 and 2006. The severe drought that enveloped the study region since 2000 was somewhat interrupted in 2004 due to a moderate snowpack and wetter than normal April. These precipitation events helped but did not replenish the already diminished water reserves in upstream reservoirs. Spring flow conditions improved markedly during 2007, as compared with 2006, and there was an extended period of time during May and June when flows exceeded 2,000 cfs at the Albuquerque Gauge (USGS Gauge 08330000). Mean daily discharge in the Rio Grande at the Albuquerque Gauge (USGS Gauge 08330000) from 1 April through 30 June 2007 ranged between 580 and 3,700 cfs (mean value= 1,690.3 cfs, SD=851.8).