Nevada Fish & Wildlife Office
Pacific Southwest Region

(Chasmistes cujus)

Class: Actinopterygli
Order: Cypriniformes
Family: Catostomidae
Genus: Chasmistes
Species: cujus
Length: up to 27.5 inches
Weight: 3.5 to 7.7 pounds
Lifespan: over 40 years
Feed: zooplankton, filamentous algae, aquatic insects
Habitat: lower Truckee River and Pyramid Lake

Official Status:


Life History:

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 one to two weeks after spawning and larval cui-ui drift downstream to Pyramid Lake shortly after hatching. Adult cui-ui typically enter the spawning run at eight to 10 years of age but may enter as early as five years of age.

Distribution and Habitat:

  Cui-ui (Chasmistes cujus) is a lake sucker found in only one place in the world; Pyramid Lake and the lower Truckee River, all within the Pyramid Lake Paiute Reservation.  It is a long-lived fish exceeding 40+ years in age and can weigh over 7.5 pounds.

This large robust sucker is long and broad.  The dorsal side of its coarsely scaled body is blackish-brown with bluish-gray cast that fades to a creamy-white belly.  It spends most of its life in Pyramid Lake, leaving only to spawn in the lower Truckee River between March and June when it reaches maturity between 6-12 years of age. Cui-ui occupy habitat near the lake bottom. They are generally found in near shore areas at depths less than 75 feet.



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.


Actions / Current Information:


  Date Title
  03/30/2005 Media Advisory: Marble Bluff Fish Passage Facility/Cui-ui Spawning Migration
Last updated: April 16, 2014