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US Fish & Wildlife Service FieldNotes

 NEVADA FWO: Moving Up The Truckee River 

Region 8, July 27, 2011
Erik Horgen, Lahontan National Fish Hatchery Complex Fisheries Biologist, measures, checks the health, and the sex of cui-ui as they make their way through the Marble Bluff Fish Passage Facility.
Erik Horgen, Lahontan National Fish Hatchery Complex Fisheries Biologist, measures, checks the health, and the sex of cui-ui as they make their way through the Marble Bluff Fish Passage Facility. - Photo Credit: n/a
Erik Horgen returns cui-ui to the Truckee River
Erik Horgen returns cui-ui to the Truckee River - Photo Credit: n/a

By Jeannie Stafford, public affairs specialist, Nevada FWO  

Each year, when spring runoff increases water flows, cui-ui (Chasmistes cujus) make their way from Pyramid Lake to the mouth of the Truckee River to begin their annual spawning migration.Cui-ui pronounced kwee-wee, are the largest of the living species of Chasmistes, weighing up to eight pounds. They are long-lived and some have been documented to live over 50 years. They now occur in only one place in the world: Pyramid Lake, Nev.

Cui-ui occupy habitat near the lake bottom and generally occur at depths less than 75 feet. They spend most of their life in the Pyramid Lake, leaving only to spawn in the lower Truckee River when they reach maturity between 6-12 years of age.

Cui-ui once occupied ancient Lake Lahontan, which covered most of northwest and central-west Nevada during the Pleistocene era. This ancient lake diminished as the climate changed until only fragmented water bodies (Pyramid, Winnemucca, and Walker Lakes) remained.

Cui-ui inhabited both Pyramid and Winnemucca Lakes prior to the 20th century. In 1905, the authorization of the construction of Derby Dam and canal resulted in diversion of the Truckee River water to the Carson River for irrigation. As a result, Pyramid Lake elevation declined more than 80 feet and water in Winnemucca Lake disappeared entirely in the late 1930s. 

 

This decline in Pyramid Lake elevation caused severe erosion and formation of a delta that prevented cui-ui from migrating into the lower Truckee River to spawn. Because cui-ui is a long-lived species, they were able to survive 19 years (1950-1969) with virtually no reproduction. On March 11, 1967, cui-ui were listed as endangered.

Following the construction of Marble Bluff Dam and Fish Passage Facility in 1976, reduction of water diversions, and the dedication of water for Pyramid Lake, the cui-ui population has increased. This year, with the assistance of Lahontan Natinal Fish Hatchery Complex staff, 900,000 cui-ui returned to their historic spawning grounds.

Contact Info: Jeannie Stafford, 775-861-6300, jeannie_stafford@fws.gov