Technical Report

Genetic Monitoring of the Rio Grande Silvery Minnow: Genetic Status of Wild and Captive Stocks in 2014

URL: https://webapps.usgs.gov/mrgescp/documents/Carson%20et%20al_2014_Genetic%20Monitoring%20of%20the%20RGSM%20Genetic%20Status%20of%20Wild%20and%20Captive%20Stocks%20in%202014.pdf

Date: 2014/12/02

Author(s): Carson E., Osborne M., Turner T.

Publication: Prepared for U.S. Bureau of Reclamation, 31 p.

Abstract:

We conducted genetic monitoring of the Middle Rio Grande population of Rio Grande silvery minnow (RGSM) annually from 1999-2012 and resumed monitoring in 2014. This work included monitoring stocks that were bred or reared in captivity and released to the Rio Grande in New Mexico since 2002. Monitoring in 2014 was based on genotyping 184 wild caught hatchery released fish (WCH), 288 wild caught eggs (WCE) from the middle Rio Grande, and 200 progeny of captive stocks, including 100 from the Southwestern Native Aquatic Resources and Recovery Center [SNARRC] and 100 from the Los Lunas silvery minnow refugium. Unmarked (wild-hatched) fish from the Middle Rio Grande were not included in the 2014 analyses because few were captured (n = 12), and fish from the Albuquerque Biological Park were not included because of failure of the captive stock prior to release of progeny into the wild in fall 2013. Genetic diversity of microsatellites and mtDNA for WCH and WCE were similar to levels observed in hatchery stocks. Mean estimates of variance effective size (microsatellites and mtDNA) for WCH and WCE were not significantly different but were significantly smaller than observed in wild fish in most previous years. Mean estimates of inbreeding effective size (microsatellites only) of WCH and WCE were lower than observed in the wild population in all previous years except 2004. Results indicate that replacement of the wild population by the hatchery population reduced variance and inbreeding effective size but genetic diversity remained similar to the wild population from prior years (1987, 1999-2012). Based on observed mtDNA variation and effective sizes of WCE from 2014, potential loss of mtDNA variation is of acute concern. Future genetic monitoring of all RGSM stocks will be critical to assess and mitigate further reductions in genetic diversity until a self-sustaining wild population is re-established.