Endangered Rio Grande silvery minnow use constructed floodplain habitat

Abstract

ABSTRACTGeomorphic changes resulting from the construction of dams, irrigation diversion structures, and flood control levees has separated the Rio Grande from its floodplain contributing to the decline of native fish species including the endangered Rio Grande silvery minnow (Hybognathus amarus). The species is currently restricted to 280‐km of the river in New Mexico. Since 2006, the New Mexico Interstate Stream Commission has constructed 121 ha of floodplain habitat between the river levees to improve habitat. To determine if constructed habitats were being utilized by the Rio Grande silvery minnow and the fish community, a presence/absence study was conducted on eight constructed floodplains during 2008 and 2009, and one natural floodplain in 2008. A total of 14 481 fish were captured in fyke nets during both years: 3528 fish were captured from constructed floodplains and 8410 were captured from the natural floodplain in 2008: 2543 fish were captured from the constructed floodplains in 2009. Of this total, 11 602 of the fish were Rio Grande silvery minnow: 2180 Rio Grande silvery minnow were collected from constructed floodplains and 7356 from the natural floodplain in 2008; 2057 Rio Grande silvery minnow were collected from constructed floodplains in 2009. Gravid female and male expressing milt were collected both years. A total of 1173 unidentified larval fish and 363 Rio Grande silvery minnow eggs were also collected during the surveys. The results show that the Rio Grande silvery minnow and the fish community utilized the constructed and natural floodplains during the spring spawning season. Copyright © 2013 John Wiley & Sons, Ltd.