Includes bibliographical references.

Introduction -- Geology -- Weather and water levels -- Morphometry -- Methods -- Lake currents --Water Temperatures -- Secchi disk transparency -- Water chemistry -- Bottom types -- Aquatic plants -- Plankton -- Benthos -- Vertical distribution of cutthroat trout -- Food of cutthroat trout -- Trout density and limnology -- Biology of Yellowstone Lake -- Summary -- Literature cited -- Appendix A points of release and recovery of drift bottles -- Appendix B A points of release and recovery of drift bottles Limnological data collected from 1954 to 1959 on surface currents, bottom currents, temperatures, bottom soils, water chemistry, plankton, bottom fauna, and higher aquatic plants are related to the biology of the cutthroat trout, Salmo clarki lewisi, in Yellowstone Lake (Wyoming). The lake, formed on Eocene lava, is oliotrophic and low in dissolved solids. Diatomus shoshone, Daphnia shoedleri, and Conochilus unicornis made up more than 90 percent of the macroscopic zooplankton by number. Upwelling in West Thumb was demonstrated by temperature stratification and conductivities. Plankton distribution and abundance were related to currents and water chemistry. Trout less than 315 millimeters in total length are not caught readily because of their feeding habits and greater dispersal. There is evidence that the heavy trout harvest in the northern part of the lake allowed Gammarus lacustris, an important food, to become locally abundant.