ROANOKE, Va. — Kim Brannock became fascinated by fly-fishing after watching “A River Runs Through It,” a 1992 film starring Brad Pitt. Years later, a co-worker taught her to fly-fish during lunch breaks, when she practiced casting underneath the St. Johns Bridge on the Willamette River in Portland, Ore.

“Besides falling in love with Brad Pitt, I fell in love with that cast,” said Brannock, who lives in Bend, Ore., and designs fly-fishing gear for Patagonia. “I was hooked.”

Women are now the fastest growing demographic in fly-fishing, one of the most male-dominated outdoor sports. That has presented a host of challenges, including finding proper gear, navigating the pitfalls of social media and even developing an awareness for self-defense skills in the outdoors.

Industry leaders say women are the only growing demographic in the sport, which is why they are so crucial to cultivate. Women make up about 31 percent of the 6.5 million Americans who fly-fish, according to the most recent study by the Recreational Boating & Fishing Foundation. In 2016, more than two million women participated in the sport, an increase of about 142,000 from the previous year.