Biology of the Utah Chub in Hebgen Lake, Montana

Abstract

The Utah chub, Gila atraria, was probably introduced into Hebgen Lake, Montana, in 1935 by bait fishermen. Randomly set gill nets indicate that chubs are concentrated in shallow areas in the spring, widely distributed in the summer and fall, and concentrated in deeper waters in winter. Stomach analyses of 165 chubs collected during the summer of 1948 show that by volume the food was 48.2 percent algae, 21.1 percent higher aquatic plants, and 24.3 percent micro-crustaceans. The 209 stomachs taken in 1953-54 contained 36 percent insects, 36 percent micro-crustaceans, 19 percent higher aquatic plants, and 9 percent debris. The peak of the spawning season in 1953 and 1954 occurred during late June and early July. Most spawning occurred when water temperatures were above 54° F. Eggs were found on different kinds of bottom, but most were recovered from sand and gravel. The average number of eggs per female was 40,750. Fry occurred along most of the shallow protected shorelines. Fry captured on July 7, 1954, averaged 0.3 inch in total length. Young taken October 1, 1943, averaged 1.3 inches. No mature males less than 3 years old or mature females less than 4 were found. Total lengths for the first 8 years of life were calculated on 475 specimens.