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Photo by Paul Thompson
Photo Courtesy of Utah Division of Wildlife Resources; Utah Division of Wildlife Resources
Least Chub
Iotichthys phlegethontis
NatureServe conservation status
Global (G-rank): G2G3
State (S-rank): S2
External links
Phenology
Spawning occurs from late April through August, and perhaps into September, the peak being in the first week of May; spawning usually occurs during the morning when light intensity is great (Crawford 1978).
Least chubs concentrate at the spring heads in July and August, moving into the marshes in September (Crist and Holden 1980).
Species range
The least chub is native to the Bonneville Basin of Utah, historically found in the freshwater wetlands surrounding the Great Salt Lake, Utah Lake, and their associated rivers and streams. However, it is now restricted to scattered springs in the western desert of Utah. Its range dramatically declined due to human impacts, particularly the introduction of nonnative fish. Only a few wild populations remaining.
Migration
Least chub do not exhibit large migrations mostly due to their size and the size of their habitats. They will, however, move from their spring habitats to warm, shallow marshes for spawning and then return to the springs. Decreasing water levels at some of their locations have had an effect on their spawning success when the channels used for this small migration become de-watered.
Habitat
The least chub utilizefreshwater springs, ponds, and marshes. They prefer areas with moderate to dense aquatic vegetation and minimal current. They rely on algae and other plants for food, shelter, and oxygen. They often move seasonally between connected springs and marshes.
Food habits
The least Chub eats primarily algae and small invertebrates. Notably they consume mosquito larvae at similar rates to the Western Mosquitofish which is a staple tool used by mosquito abatement districts. The UDWR and local mosquito abatement districs are working together to find situations where Least Chub can take the place of Mosquitofish to control mosquito Larvae.
Reproductive characteristics
Least chub females may mate with multiple males, and are intermittent and partial spawners meaning they release a small number of eggs over an extended season (April to August) rather than all at once. Spawning occurs in vegetation, mainly algae, where the adhesive fertilized eggs attach, while no parental care is provided.
Threats or limiting factors
The primary threats to Least Chub populations continue to be increased human water use that decreases their available habitats. Additionally introduced species can prey upon or compete with Least Chub. An exceptionally detrimental species is the mosquitofish that competes with adult Least Chub for resources and will prey upon young Least Chub.
