BRANFORD, Fla. — “Lots of artillery out there,” an old man hollered from the safety of the Suwannee River’s edge, and he was right. The sturgeon were jumping high and fast, twisting their armored girth in midair and returning to the depths with a stunning splash.

On the water, there was reason to be anxious. Florida’s season of “sturgeon strikes” — law enforcement’s term for collisions between the state’s largest freshwater fish and hapless boaters — was already well under way.

It may seem bizarre, but it is no joke. Leaping sturgeon have injured three people on the Suwannee this year, including a woman on a Jet Ski and a girl whose leg was shattered when one of the giant fish jumped aboard her boat. Eight others were hit last year, and with traffic growing on the storied river, sturgeon are joining alligators and hurricanes on the list of things to dread in Florida.

“These injuries are very impressive,” said Dr. Lawrence Lottenberg, director of trauma surgery at the University of Florida College of Medicine in nearby Gainesville. “You’ve got people sitting on the front of an open boat, and the boat is going 20, 30, 40 miles per hour. The fish jumps up and usually slaps these people right across their face and upper chest. Almost every one of them universally has been knocked unconscious. If you’re not wearing a life jacket, you’re going to fall in the water and potentially drown.”