Cooperative Fish and Wildlife Research Units Program: Utah
Education, Research and Technical Assistance for Managing Our Natural Resources

The Rio Grande Silvery Minnow (RGSM, Hybognathus amarus) is listed as endangered under the ESA and remains critically imperiled in the Middle Rio Grande River. Although there is existing information on their basic habitat and life histories, there are many critical data gaps. These pelagic spawners release semi-buoyant eggs in the water column and rely on floodplain connectivity for rearing, after drifting downstream and being retained in available habitats. Habitat alteration, loss of inundated floodplains, and alteration and dampening of the hydrograph have negatively impacted the species through reduction in floodplain connectivity, and in the absence of floodplain connectivity, the eggs drift further causing upstream persistence of the species to become reliant on the ability of these fish to move upstream to recolonize areas above. This project aims to describe and quantify the ability to move and drivers of RGSM movement in its contemporary fragmented habitat. To do this, we are releasing PIT-tagged RGSM into the Middle Rio Grande River and tracking their movement during differing environmental conditions and seasons with a combination of stationary and mobile PIT-tag antennas. The project is a collaboration of researchers across multiple agencies and includes the U.S. Bureau of Reclamation and U.S. Fish and Wildlife Service. Our project will inform the design and implementation of future modifications to dams in the Middle Rio Grande aimed at allowing fish movement in the upstream direction in particular.