Restoring Gray Redhorse populations in the Delaware River, New Mexico

Authors: Joanna Hatt, Daniel Trujillo, John Caldwell

Year: 2019

Abstract

The Gray Redhorse, Moxostoma congestum, is a species native to the Gulf Coastal drainages of central and west Texas, the Rio Grande and Pecos River in Texas and New Mexico, and Mexican tributaries to the Rio Grande downstream of the Big Bend region. Gray Redhorse are listed in New Mexico as endangered and the American Fisheries Society Endangered Species Committee considers this species to be threatened [Jelks et al., 2008, Fisheries 33(8):372-407]. By 2008, only two populations were known to persist in New Mexico. Fish kills resulting from blooms of toxic golden algae, Prymnesium parvum, were largely responsible for this extirpation event. Following an extensive survey effort, the New Mexico Department of Game and Fish, in cooperation with the Bureau of Land Management, initiated a reintroduction of Gray Redhorse to the Delaware River in 2012. Multiple years of habitat restoration of the Delaware River provided suitable conditions for repatriation of this species of conservation concern. Forty-four adult redhorse were captured in the Black River and translocated to the Delaware River between 2012 and 2018. These individuals were introduced to a site containing a translocated population of Texas Hornshell, Popenaias popeii. As Gray Redhorse serve as a primary host for the glochidia stage of the mussel, repopulating the Delaware River with this species is equally important to the long-term viability of Texas Hornshell. Annual monitoring of the restoration site has occurred since 2013 and multiple young-of-year Gray Redhorse were detected between 2016 and 2018. The creation of a third population reduces the risk of extirpation of Gray Redhorse and Texas Hornshell in New Mexico. Future priorities for this recovery effort include improving fish passage on the Delaware River and identifying additional restoration sites in New Mexico.