The Cui-ui (Chasmistes Cujus) is a large sucker fish which is endemic to Pyramid Lake in northwestern Nevada. It feeds primarily on zooplankton and perhaps on nannoplankton (such as algae and diatoms). Maximum size of male Cui-ui is approximately 21 inches (530 millimeters) and 3.5 pounds (1.6 kilograms) while females reach approximately 25 inches (640 millimeters) and 6 pounds (2.7 kilograms).
The Cui-ui is anadromous, and will attempt to ascend the Truckee River to spawn in mid-April. If inflow is insufficient to permit this, the cui-ui may attempt to spawn in Pyramid Lake, but generally with little success due to the salinity of that lake. Water releases from the Boca and Stampede reservoirs is currently timed to assist the spawning run, although in drought years this water is reserved for the Reno metropolitan area. Several hatcheries are maintained by the Paiute nation to ensure that such a situation does not impact the long term viability of the Cui-ui. These measures have greatly increased Cui-ui populations, although it is still listed as an endangered species.
