IOWA CITY, Iowa (AP) The teams of fishermen arrived with a seemingly unusual array of equipment - loud airboats, powerful searchlights and scores of bows and arrows.
Since their tournament on the Mississippi River ended last month, it's drawn enough complaints that regulators are 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 eardrums 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 Iowa Department of Natural Resources said Wednesday that it is investigating the event after a legal review determined organizers failed to obtain a required permit.
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.
The competition featured 43 teams, many using boats with aircraft-style propellers and powerful engines to zip across the water and low-lying land from dusk until early morning. They went after only invasive fish such as carp and gar. Cash prizes went to teams with the most fish (318) and the heaviest 20 fish (380 pounds).
While the contest thrilled the 130 participants who came from as far away as Alabama, some campers and cabin dwellers along the river complained of loud noises, lights and potential disturbances to habitat and wildlife.
Mason said he was able to read a newspaper at 2:30 a.m. and could hear boats coming from 3 miles away. He questioned the effect of the boats on water lotus and other plants that were in bloom, as well as river otters, bald eagles and other animals.
Tournament Director Matt Harris downplayed the complaints and defended bowfishing as a proper use of the protected area.
''It's just something a lot of people along the river aren't used to seeing, a lot of boat traffic at night,'' Harris said. ''At least where I was shooting, I can't really see how our boat noise would be anything that would be all that disruptive.''
He noted that the huge harvest of invasive species - which was donated as feed to a pig farm - benefits populations of native fish.
Mason and a national watchdog group, Public Employees for Environmental Responsibility, argue that the tournament blatantly violated the U.S. Fish and Wildlife Service rules for the refuge, which extends for 260 miles in Minnesota, Wisconsin, Iowa and Illinois. It was established in 1924 to protect fish, wildlife, plants and migratory birds.
The critics want the agency's Midwest regional office to review the agency's hands-off approach to the event and to consider enforcement action against the organizers, who did not obtain permits or give advance notice. The agency should also consider whether to allow large bowfishing tournaments in a refuge, said Jeff Ruch, executive director of the watchdog group.
''It's a big, noisy, new thing that is pretty fascinating,'' Ruch said of the sport.
Bass Pro Shops calls bowfishing ''one of the hottest outdoor archery activities.'' Supporters say that the number of tournaments, such as the two-day Battle on the River that begins Saturday at Tennessee's Kentucky Lake, is increasing.
But they are also running into regulatory roadblocks in some cases.
Rules for the Mississippi River refuge call for tournament organizers to obtain for permits from state natural resources agencies. They also call for minimizing any effects on other users, providing advance notice and prohibiting the ''unreasonably disturbing'' use of power equipment and lights.
The tournament, headquartered at the retailer Cabela's in Prairie du Chien, Wisconsin, revealed a number of concerns as airboats and bowfishing become more popular, said Sabrina Chandler, supervisor of the refuge.
The Fish and Wildlife Service only learned of the two-day tournament a few days in advance, when officers saw an increase in airboats arriving early for pre-fishing, she said.
''We were very much caught off guard with this one,'' Chandler said.
She said the agency received a number of complaints but did not take action, noting its officers do not enforce noise violations and leave that up to states.
As for fish and wildlife, she said, it's not clear what impact airboats have but ''it is something we're looking into.''
Chandler said the event fell into an exemption under Wisconsin's rules for fishing tournaments, which do not require permits for regional events. She called that a loophole, saying it may be closed next year when the agency rewrites its rules.
The Wisconsin Department of Natural Resources said Wednesday that the exemption for regional tournaments was appropriate and should not be changed.
Iowa DNR spokesman Kevin Baskins said agency officials were initially confused about whether the tournament needed an Iowa permit but concluded Wednesday that it did. He said the violation is a simple misdemeanor, but it's not clear whether enforcement action will be pursued.