Official Status: Endangered
Distribution and Habitat:
Cui-ui are obligate lacustrine suckers with a very restricted distribution, occurring only in Pyramid Lake, western Nevada. Cui-ui were extirpated from nearby Lake Winnemucca which dried up in the late 1930's following diversions of the Truckee River. Cui-ui also occupy the lower Truckee River during the spawning season. Anecdotal evidence suggests that historical spawning runs went as far upriver as Reno, Nevada (about 100 km upriver from Pyramid Lake). Currently, most cui-ui migrate only as far as 15 to 20 km upriver.
Cui-ui are benthic fish, occupying habitat near the lake bottom. Most are found in near shore areas at depths less than 23 m (75 feet), although some have been captured deeper. Little is known about juvenile or larval habitat associations in Pyramid Lake.
Cui-ui migrate up the lower Truckee River to spawn between March and June each year and return to Pyramid Lake after spawning. Migrating adults must be passed through Marble Bluff Fish Facility and above Marble Bluff Dam to access suitable spawning habitat. Timing of the spawning migration depends on river water temperature and flow characteristics. Spawning occurs over gravel. No nests are built; the adhesive eggs are broadcast over a large area. Eggs hatch 1 to 2 weeks after spawning and larval cui-ui drift downstream to Pyramid Lake shortly after hatching. Adult cui-ui typically enter the spawning run at 8 to 10 years of age but may enter as early as 5 years of age.
Physical barriers pose a threat to cui-ui spawning migrations. Low water conditions and/or sand bars can render the delta at the mouth of the Truckee River impassable. Cui-ui must also be passed through Marble Bluff Fish Facility and above Marble Bluff Dam to access suitable spawning habitat.
Migrating adults require deep pools and other cover, which are generally not available in the lower Truckee River below Marble Bluff Dam. These conditions can promote stress during spawning runs.
Listed as Endangered on March 11, 1967.