IOWA CITY, Iowa  — The teams of fishermen arrived with a seemingly unusual array of equipment — loud airboats, powerful searchlights and scores of bows and arrows.

After their tournament on the Mississippi River ended, it had drawn enough complaints that federal regulators were considering tighter restrictions on the fast-growing but little-known sport of bowfishing, in which anglers shoot fish with arrows attached to fishing line. The competition took place at night, with teams using bright lights to spot their prey.

“It turned night into day and blasted our ear drums like we were on an airport runway,” said Tim Mason, an environmental activist from McGregor, Iowa, who spends summers with his wife on a houseboat in the area.

The grumbling began soon after members of the Bowfishing Association of America gathered late last month for a world tournament in western Wisconsin and northeastern Iowa, home to the Upper Mississippi River National Wildlife and Fish Refuge.