Specimens of Gyrodactylus macrochiri were collected from bluegill, Lepomis macrochirus and largemouth bass, Micropterus salmoides, in Walter F. George Reservoir at 2 week intervals from December 1967 to January 1969. The G. macrochiri populations were at high levels during the hosts' spawning in the spring, at temperatures similar to the spawning period in the fall period and during winter. During mid-summer at temperatures above 28 C the populations on both host species were at their lowest levels.