Technical Report

Rio Grande Silvery Minnow Rescue and Salvage - 2006

URL: https://webapps.usgs.gov/mrgescp/documents/USFWS_2007_RGSM%20Rescue%20and%20Salvage%20-%202006.pdf

Date: 2007/03/13

Author(s): USFWS

Publication: Prepared by U.S. Fish and Wildlife Service, 40 p.

Abstract:

This report documents efforts during 2006 to reduce the mortality of post-larval Rio Grande silvery minnows (Hybognathus amarus, silvery minnow) when flow in the Middle Rio Grande became intermittent and it discusses the effectiveness of those efforts using the limit of incidental take as the standard of performance. The limit of incidental take was defined in the March 17, 2003 Biological Opinion (U. S. Fish and Wildlife Service, 2003; March 17, 2003 BO) and modified on August 15, 2005 (U. S. Fish and Wildlife Service, 2005a) and June 15, 2006 (U. S. Fish and Wildlife Service, 2006a). As amended, the incidental take is now estimated annually for the period April 1 through March 30 using a formula that incorporates monitoring data from October of the previous year, habitat conditions during the spawn (spring runoff), and augmentation. Estimates of incidental take are derived from surveys in which observed mortality is multiplied by 50, based on the assumption that the probability of observing a single mortality is 0.02. The June 15, 2006 amendment also specifies that the incidental take statement applies to silvery minnows larger than 30 mm standard length or approximately 35 mm total length. The amended incidental take limit that applied to 2006 was 13,296,774 and is equivalent to 265,935 silvery minnows observed dead, restricting observations to silvery minnows larger than 30 mm standard length or approximately 35 mm total length.