The Bonneville cisco, Prosopium gemmifer, is one of three whitefish species endemic to (found only in) Bear Lake on the Utah-Idaho border. Bonneville cisco generally inhabit deep cool water. During their January spawning period, however, individuals move to shallow water, where they form large schools and spawn over the lake's limited rocky areas.
Bonneville cisco eat small aquatic invertebrates. Individuals generally do not exceed 230 mm total length, and are easily distinguished from the other whitefish in Bear Lake by their pointed mouths, slender bodies, and absence of spots. Bonneville cisco are a popular sport fish only during their spawning period, when they are captured in great numbers through the use of dip nets.
A diminutive fish found only in Bear Lake. The Bonneville cisco is a long, slender, pearly-silver fish that rarely grows beyond seven inches. It has a dusky blue back and a brassy band along its flanks at spawning time. The snout is sharply pointed. It is noted for its mid-winter spawning concentrations along a rocky beach on the east side of Bear Lake in mid-January where it is dip netted in large numbers. It is a prolific fish that is an important forage for the predatory species in Bear Lake.
(Photo and information courtesy Utah Division of Wildlfe Resources)