BOZEMAN, Mont. — Bud Lilly, a fly-fishing legend, guide, conservationist, and catch-and-release pioneer, died Wednesday of congestive heart failure at a Montana care center, his son Chris said. He was 91.

Mr. Lilly, whose clients included Jimmy Carter and Tom Brokaw, was an ambassador not only for the sport of fly-fishing but also for his home state of Montana.

Writer Arnold Gingrich, cofounder of Esquire Magazine, called Mr. Lilly ‘‘a trout’s best friend,’’ which later became the title of Mr. Lilly’s 1988 autobiography.

A native of Manhattan, Mont., the Navy veteran graduated from Montana State University and taught school for several years before buying what became Bud Lilly’s Trout Shop in West Yellowstone in 1961.

In the 1960s, many Montana rivers were ‘‘put-and-take’’ fisheries, with the Department of Fish, Wildlife and Parks planting hatchery trout and anglers catching them.

Some trout shop customers from the East Coast talked to him about catch-and-release.

‘‘It made sense to me,’’ Mr. Lilly told The Montana Standard in a 2015 interview.

Mr. Lilly began advocating for catch-and-release fishing and eventually led the effort to get the state to stop stocking fish in rivers such as Madison, now renowned as a wild trout fishery. ‘‘He was a real leader in a lot of things that have shaped where we are right now,’’ said John Bailey, who runs Dan Bailey’s Fly Shop in Livingston.