Fishermen are famed for overstating the size of their catches, but science has found an instance in which anglers have apparently underestimated their prowess. New research indicates that sport fishermen are taking an unexpectedly big toll on saltwater fish populations, in some cases landing even more fish than their commercial counterparts.

The most comprehensive survey ever conducted of U.S. saltwater recreational catches suggests that several species -- including red snapper, red drum and bocaccio -- are unlikely to recover unless sport fishing comes under greater regulatory control.

"The perception of their impact is quite different from the reality," said study leader Felicia C. Coleman of Florida State University. "If we're going to manage these stocks in a sustainable way, we can't ignore the recreational component."

An estimated 10 million Americans engage in saltwater fishing, a sport that encompasses everything from lone fishermen to party boats holding 100 people or more. The industry grew 20 percent in the past 10 to 20 years and is valued in the tens of billions of dollars.

Some sport fishing groups offered cautious support for the study, saying it would help protect the environment they cherish. Others rejected it as inaccurate.

"It's a whole bunch of malarkey," said Jim Donofrio, executive director of the Recreational Fishing Alliance, a New Jersey-based group claiming to have 75,000 members.

"Most of the water contains none of the fish most of the time," Donofrio said. "You may see a lot of boats in the water, but that doesn't mean they're catching."

The new study looked not at boats but at catches over the past 22 years, tallied primarily by states and the Commerce Department's National Marine Fisheries Service. By filling in gaps in those databases, the team determined that 5 percent of U.S. marine catches are recreational. That is more than double previous estimates, they reported yesterday in the online edition of the journal Science.

More important and more surprising, the researchers said, was that sport fishing accounted for 23 percent of catches of the most overfished species -- sometimes trumping trawlers.

In the Gulf of Mexico in 2002, for example, recreational fishers accounted for 64 percent of all catches of what the NMFS calls "populations of concern," including red and vermilion snapper, and the greater amberjack. Off the Pacific Coast, 59 percent of the landings of overfished species -- including ling cod, bocaccio and various species of rockfish -- were attributable to recreational fishers.

In the South Atlantic, 38 percent of landings of fish of concern, including the red drum popular in blackened fish recipes, were recreational. In the Northeast and Mid-Atlantic, including Maryland and Virginia, the figure was 12 percent.

Only fish brought to shore were counted; many others are tossed back dead or nearly so.

"This issue is a lightning rod for the recreational fishing community," said Michael Sutton, who directs the marine fisheries program at the David and Lucile Packard Foundation. "This is the white elephant in the room that no one wants to talk about and no one even wants to know about."

Commercial fishing within 200 miles of the U.S. coastline is regulated by federal law, but recreational fishing is mostly under state control, and laws vary considerably. Most states impose limits on the number of fish of each species that a person can catch, when they can be sought and the minimum size fish must be to be kept. But given the absence of limits on the number of people allowed to fish -- some states do not require licenses -- those limits offer inadequate protection for many species, Coleman and others said.

"While the individual may take relatively few fish, we show that a few fish per person times millions of fishermen can have an enormous impact," said study co-author Will Figueira, now at the University of Technology Sydney in Australia.

The researchers suggest tighter licensing requirements and other limits on sport fishing, to be individualized by area and species.

The survey said regulatory control of sport fishermen is needed to help struggling species of fish recover.