This cute little fish lives in the Upper Rio Grande drainage in south-central Colorado and New Mexico, into Durango and Zacatecas in Mexico. A few were also accidentally introduced into the South Platte near Denver and into the San Francisco River in Arizona, probably from bait buckets. Suckers, as the name suggests, live on the bottom of rivers and occupy lower trophic levels, similar to the Rio Grande chub we discussed back in issue #52. As adults, they feed on algae on river bottoms.
Like all suckers, this one has thick lips and a mouth located on the bottom of the face, as well as a long pharyngeal bone in the throat that also has a line of teeth. Suckers evolved sometime around the Middle Eocene (36.2 million years) and the oldest specimens are from Colorado and Utah.
Like all native fish we have discussed here, the Rio Grande Sucker’s population has declined since Euro-American settlement in the region. Habitat loss, damming of rivers for agricultural use, environmental degradation, and the introduction of non-native fish have all made life harder for these little guys. As a result, they are considered critically imperiled in Colorado.