Fishery biologists working in lentic waters have long been in need of fish collection gear that could be used to select fish of a desired species or size. Equipment described were developed to meet this need during trout investigations in Yellowstone Laek. Refinements have been incorporated into the Yellowstone electrofishing shocker boat. Yellowstone Lake is optimum for use of the shocker. Large numbers of cutthroat trout, 3 to 18 inches long, were captured in the summer of 1963 and no losses were incurred. Under average shocking conditions, 75 to 100 adult cutthroat trout are captured per hour. All species of fish encountered were readily attracted to the positive electrode.