The least chub, Iotichthys phlegethontis, is a small minnow native to the Bonneville Basin. Although the species formerly occurred in many areas of the Bonneville Basin, including ponds and streams near Salt Lake City and the Great Salt Lake, it now occurs only in scattered springs and streams in western Utah. Much of the least chub's decline can be attributed to the introductions of nonnative fishes. Fortunately, efforts are now underway to expand the numbers and distribution of the least chub.

Spawning occurs during the spring and early summer. Eggs are fertilized in the water, and then sink until they attach to vegetation or the substrate. No parental care is given to eggs or young. Least chub eat primarily algae and small invertebrates, including mosquito larvae. The least chub is a schooling species that prefers areas of dense vegetation in slow-moving water.