Overview
The June Sucker (Chasmistes liorus) is an endangered, long-lived lake sucker found naturally nowhere else on Earth outside Utah Lake in central Utah. Named for its historic mass spawning runs that occurred every June up the Provo River, it is an extraordinary midwater filter-feeding sucker that serves as the flagship conservation species for the ecological restoration of Utah Lake.
Biology and Physical Characteristics
Unlike typical bottom-vacuuming suckers, the June Sucker has a wide, terminal mouth that angles upward at a 45-degree angle, with thin, smooth lips lacking papillae. Its body is streamlined and cylindrical, colored dark olive-brown to slate on the back with pale silvery sides and a white belly. Inside its throat, it possesses fine, closely spaced gill rakers adapted for straining microscopic zooplankton from open lake water.
Behavior and Ecology
For most of the year, June Suckers roam the open pelagic waters of Utah Lake, swimming through zooplankton blooms. Each June, mature adults congregate at the mouth of the Provo River, embarking on upstream spawning migrations to broadcast eggs over clean, well-aerated gravel riffles before returning to the lake.
Conservation and Human Impact
Listed as Endangered by the IUCN, the June Sucker was downlisted from Endangered to Threatened under the US Endangered Species Act in 2021 following heroic multi-decade recovery efforts. Historic threats included agricultural water diversion, severe habitat modification of the Provo River, and predation by introduced common carp and white bass.
Interesting Factoid
Unlike almost all other suckers that feed with vacuum-cleaner mouths pointed straight down at the mud, the June Sucker has an upturned mouth that points forward to scoop floating plankton out of midwater.