Habitat associations of the Rio Grande Silvery Minnow, an endangered desert river fish, from a retrospective analysis based on a period of high abundance.

This article focuses on characterizing the mesoscale habitat associations of the Rio Grande Silvery Minnow (Hybognathus amarus), a federally endangered desert river fish and the only remaining wild pelagic broadcast-spawning species in the middle Rio Grande, New Mexico. Based on extensive sampling from 1994 to 1996 at two sites spanning the species’ range, the study found that the minnow preferentially occupies shallow (≤25 cm), low-velocity (≤15 cm/s) mesohabitats such as pools, backwaters, and runs with fine substrates (primarily silt and sand), despite these habitats being less frequently available in the river. The findings highlight the importance of restoring and maintaining hydraulic diversity—particularly shallow, low-velocity habitats—to support the species’ life history needs and inform conservation and habitat rehabilitation efforts in a river system heavily modified by flow regulation and channel alteration.