Annual Report

Rio Grande Silvery Minnow Health Study


Date: 2012/12/01

Author(s): Lusk J.D., Davis A.P., Osborne M.J., Papoulias D.M., Woodland J.E., Remshardt W.J.

Publication: United States Fish and Wildlife report prepared for the United States Bureau of Reclamation under Interagency Agreement 06-AA-40-2548


It is widely known that the health of fish can be adversely affected by exposure to water pollution. In 2005, the Middle Rio Grande Endangered Species Act Collaborative Program (Collaborative Program) requested proposals for monitoring the health conditions of Rio Grande silvery minnow (Hybognathus amarus; RGSM) in the mainstem of the Middle Rio Grande. In response, the U.S. Fish and Wildlife Service (Service) designed the RGSM Health Study to monitor and characterize the health conditions of RGSM in the MRG to provide baseline data on diseases and parasites, and document external and internal anomalies and pathologies in fish collected throughout the year. The Collaborative Program also requested that monitoring of RGSM health conditions be conducted in conjunction with a water quality monitoring program to better link results to possible causes. In particular, the New Mexico Environment Department (2009) implemented (and reported separately) a companion water quality study that overlapped some of the same sites sampled during this RGSM Health Study.

Various agencies participated in the RGSM Health Study including the New Mexico Environment Department (NMED); the University of New Mexico, Museum of Southwestern Biology (Museum); the U.S. Geological Survey (USGS), New Mexico Ecological Services Field Office, and Dexter Fish Health Unit. We conducted the RGSM Health Study from July 2006 to July 2008 (Year 1 and Year 2). Rio Grande silvery minnows (Hybognathus amarus) were collected nearly every three months from six sites in the Rio Grande from Bernalillo to San Antonio, New Mexico. We used a suite of standard methods of observation of fish health conditions during necropsy to determine total length, mass, organ condition, the number and type of lesions and anomalies, the number and type of parasites and pathogens, and we analyzed their tissues for a variety of chemicals and genetic conditions. We also measured surface water quality parameters (i.e., dissolved oxygen (DO), oxygen saturation, temperature, pH, specific conductivity).

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