Two Ocean Lake, which was annexed to Teton National Park in 1950, was reported by long-time residents of the area and by the Wyoming Game and Fish Commission to have experienced a tremendous increase in chub which followed a sharp decline in trout, Salmto clarki lezwisi. During the rise of the chub, residents of the area made a concerted effort to annihilate the great blue heron, Ardea herodias. It was also reported that the lake contained an unusually high frequency of deformed chub (curvatures of the vertebral axis). Under the protection of the National Park Service and a proposed restoration of the lake, a rise in trout and heron, two of the main predators of the chub, might be expected. This suggested an opportunity for a study of predation in nature with special reference to predation on deformed chub. Field studies, carried out in the summers of 1956 and 1957, were directed toward an evaluation of the problem-basically a study of the ecology and life history of the chub with special interest in the question of whether or not it would be possible in future years to detect and attribute a decrease in deformed chub to the anticipated increase in predators. This would require estimates of the annual abundance of deformed chub, which would require a knowledge of their distribution in the lake relative to that of the normal chub. Aside from statistical applications, information on the distribution might have a bearing on the question of the causes of the deformity. Is the cause environmental, hereditary, or some combination of the two? Also, comparative rates of survival of normal and deformed chub under existing low predation should be determined. Finally, a comparison of the frequency of deformities in the Two Ocean Lake population with that in other populations should be made to aid in determining whether or not the Two Ocean Lake situation is unique, as has been reported. I think it is important to mention in passing that This work was supported by a grant from the National Science Foundation through the Jackson Hole Biological Research Station of the University of Wyoming and the New York Zoological Society. I wish to acknowledge the very able assistance of Ross M. Horrall in 1956 and of Irvin Lawrence in 1957. the field work and laboratory experiments sought to answer these questions, and did yield a valuable backlog of information. But many aspects remain insufficiently known to report. This paper presents findings on (1) the limnology of the lakes (2) the ecology and life history of the chub (3) the frequency of deformed chub in different lakes, and (4) the distribution of chub in Two Ocean Lake. The results are derived primarily from Two Ocean Lake, and secondarily from Emma Matilda, Ox Bow, and Enos lakes. All of the lakes are in the Snake River drainage.