Includes bibliographical references (pages 24-25).

Scale collection and reading. Growth calculations. Age composition. Relations of age and growth to fishing pressure. Summary. Literature cited. Appendix A -- Body-scale relation. Appendix B -- Lee's phenomenon. Appendix C -- Calculated lengths. Appendix D -- Growth compensation. Age composition, growth rate, and year-class strength of Yellowstone Lake cutthroat trout from collections made in 1948 and from 1950 to 1959 are analyzed to relate total catch changes in age composition and growth rate. An increase in growth rate of fish fully recruited to the fishery and a decrease in percentages of fish belonging to age groups VI and VII are attributed to an increase in fishing pressure. Mean age of the catch varied with year-length of the catch has remained high, suggesting that production is more efficient now than in past years. Maximum equilibrium yield may be near. If the catch continues to increase at the present rate, it may become excessive within the next few years.