Technical Report
Rio Grande Silvery Minnow Rescue and Salvage Fiscal Year 2004
Date: 2005/04/11
Author(s): USFWS
Publication: Prepared by U.S. Fish and Wildlife Service, 11 p.
Abstract:
This report documents efforts during 2004 to reduce the magnitude of adult (greater than 30 mm TL) Rio Grande silvery minnow (Hybognathus amarus, silvery minnow) mortality due to intermittent and near intermittent conditions and evaluates the effectiveness of those efforts using the limit of incidental take defined in the March 17, 2003 Biological Opinion (U. S. Fish and Wildlife Service, 2003; BO) as the standard of performance.
Prevailing drought conditions in 2004 resulted in water shortages throughout the Middle Rio Grande, New Mexico. Flows in the Rio Grande began to recede on June 16, 2004. Ultimately, 68 miles of the Middle Rio Grande were dewatered upstream of the South Boundary of Bosque del Apache National Wildlife Refuge (NWR) to a point several miles downstream of the Isleta Diversion Dam. This necessitated that the silvery minnow be salvaged from isolated pools as the river receded to reduce the probability that the mortality associated with water operations would exceed the limit for post-larval incidental take as established in the March 17, 2003 BO. A total of 12,865 silvery minnows, mostly young-of-year, was documented to exist in the dewatered reaches of river. Of these, approximately 92.5% were transported alive to Albuquerque Reach of the Rio Grande where they were released. Incidental take of adult silvery minnows (greater than 30 mm TL) that occurred as a result of water operations in the Middle Rio Grande was 521 – within the limitations established in the March 17, 2003 Biological Opinion. “The Service anticipates that up to 38,000 silvery minnows (greater than 30 mm [1.2 in]) may be taken in any year due to the Federal and non-Federal actions described and analyzed in this biological opinion (Service, 2003).â€