Flannelmouth suckers (Catostomus latipinnis) are native to the Colorado River system, including the Fremont River. They are herbivorous and ascend streams in the spring to spawn. In recent times, Utah flannelmouth sucker populations have been reduced in both numbers and distribution, primarily due to flow alteration, habitat loss/alteration. The species is included on the Utah Sensitive Species List. These benthic (bottom-dwelling) fish primarily eat algae, although invertebrates and many types of plant matter are also consumed. Mountain Sucker. Mountain suckers (Catostomus platyrhychus) are native to Utah's Bonneville Basin, as well as the Colorado River system. They are probably present, but unconfirmed, in the park. These benthic (bottom-dwelling) fish eat algae, higher plants, and occasionally invertebrates. Mountain suckers are small and usually 6-8 in (15-20 cm) in length.