A 2009 study, published in the North American Journal of Fisheries Management, found that in lakes with yellow perch and no ciscoes, walleyes grew more quickly to sexual maturity--12 to 17 inches. But in lakes with ciscoes and no yellow perch, walleyes grew more frequently to trophy size--30 inches or more. These trophy walleyes ate bigger ciscoes--possibly up to 12 1⁄2 inches--but were more likely to have empty stomachs. In some fish, ciscoes accounted for as much as 55 percent of prey by weight, but only 18 percent by item. Consuming fewer but more substantial meals left the fish with more energy for growth.