In the United States, catch and release was first introduced as a management tool in the state of Michigan in 1952 as an effort to reduce the cost of stocking hatchery-raised trout. Anglers fishing for fun rather than for food accepted the idea of releasing the fish while fishing in so-called "no-kill" zones. Conservationists have advocated catch and release as a way to ensure sustainability and to avoid overfishing of fish stocks. Lee Wulff, a New York-based fly angler, author and film maker, promoted catch and release as early as 1936 with the phrase "Game fish are too valuable to be caught only once." Don Martinez a West Yellowstone, Montana fly shop owner promoted catch and release in his 1930–40s newsletters sent to Eastern anglers.