Habitat use of the Rio Grande silvery minnow (Hybognathus amarus) during a long-term flood pulse in the Middle Rio Grande, New Mexico

Abstract

The Middle Rio Grande (MRG) of New Mexico has been influenced by man for over 500 years. Native Americans began diverting water to irrigate agricultural crops in the floodplain in the 14th century. The Spanish followed and increased agricultural irrigation to over 125 000 acres. Frequent flooding of the MRG valley in the 19th century led to many engineering projects in the early 20th century to control flooding. A series of impoundment dams, di- version dams, and levees were constructed. The loss of floodplain habitats throughout the MRG Valley has altered the riparian community and caused the demise of many fish species. A controlled flood pulse from Cochiti Reservoir, New Mexico was initiated in April 2005 to support the recovery of the endangered Rio Grande silvery minnow, Hybognathus amarus. This study documents habitat selection by larval fishes in a restored floodplain in the Rio Grande, NM. Larval fish light traps captured 394 larvae representing four cyp- rinid species (Pimephales promelas, H. amarus, Cyp- rinella lutrensis and Cyprinus carpio). Results for CCA indicate that Hybognathus amarus prefer shal- low, low velocity habitats. Results from Chao-Jaccard similarity index indicated that relative contribution was highest in P. promelas at 64% followed by H. amarus 33%. Results from (dis)similarity analysis re- veal that species composition between habitat orienta- tion and date was highest in H. amarus at 42% followed by P. promelas 40%. Cyprinella lutrensis and C. carpio represented 9.5 and 8.5%, respectively. A general linear model indicated that only depth and velocity were significantly different (p00.02 and p0 0.03 respectively).