The Bonneville whitefish, Prosopium spilonotus, is one of three whitefish species found only in Bear Lake on the Utah-Idaho border. Bonneville whitefish prefer cold water, and stay in cool deep areas of the lake during the summer months. The species is the focus of limited fishing pressure, primarily during its spawning period.
Bonneville whitefish form large schools and congregate over limited rocky areas in the lake to spawn during November and December. The species eats a variety of aquatic invertebrates, as well as fish eggs and fishes.
Bonneville whitefish obtain larger sizes than Bear Lake whitefish or Bonneville cisco, often growing to over 400 mm in total length. Large Bonneville whitefish are whitish in color, whereas small individuals have dark spots on their backs, making them almost indistinguishable from Bear Lake whitefish. Scale counts are the best way to distinguish the two species.
This species of native fish is indistinguishable from Bear Lake Whitefish below 10 inches in length. The Bonneville whitefish have gray-blue spots along their sides. These whitefish are elongated, relatively cylindrical fish. They are silvery-white along their sides grading into a charcoal gray to black on their backs. They have small delicate mouths that make them difficult to catch. Bonneville whitefish may reach four pounds and grow to 20 inches. Both species occur only in Bear Lake and nowhere else in the world. Another species of whitefish, which lives in mountain streams, is the Mountain Whitefish.
Whitefish are part of the trout family (Salmonidae). They have one distinguishing characteristic that puts them there and that is an adipose fin. The Bonneville whitefish are "cousins" with the mountain whitefish, which are found in many streams and some lakes here in Utah and the western US. Bonneville Whitefish have very large mouths compared to their cousins and for a good reason. Bonneville Whitefish are predators once they reach about 14" or so, whereas the Mountain Whitefish eat pretty much just insects their whole life.
Whitefish are not chubs. However, whitefish do have many common (colloquial) names. Some of the more common ones are: herring, cisco, tulibee, rounds, Menominee, and whiteys.