Klamath Largescale Sucker

This species is endemic to the Klamath River basin in northern California and southern Oregon, within the Western United States. In addition, although outside of its main range, species have also been observed as far north as British Columbia and far east as Montana. Habitat includes rocky pools and runs of creeks and small rivers, lakes, and reservoirs. Adult Klamath Largescale suckers likely lived in deep lake habitats, while juveniles stayed in streams or along lake margins. Today, several larger streams still support breeding populations. Adults have been found both near-shore and offshore in Upper Klamath Lake. They are most often found in large streams where water quality is fairly high, but can also be found in lakes. However, they cannot survive long in water temperatures that exceed 32°C and where dissolved oxygen levels are around 1 mg/L. Historically, they were likely more abundant in deep water lakes.

The species is a benthic omnivore. It is found among a variety of freshwater systems, such as lakes, rivers, and sloughs, respectively. Juveniles' diet consists of zooplankton; adults consume snails, worms, macro-invertebrates, and plant/algae material among the substrate.