DRY TORTUGAS NATIONAL PARK, Fla. (AP) -- Reeling in a 45-pound grouper used to be just an average day on the water in the Florida Keys. The abundance of behemoth fish attracted anglers from around the world in the early 1900s, including adventurers such as Ernest Hemingway and Zane Grey, who pulled in monsters from the clear, warm depths off Key West.
But as Florida's population boomed, the attraction that drew them began to vanish. Anglers were snapping up the larger fish by the thousands. An average grouper caught in the Keys now is about eight pounds.
"We were starting to look like a Third World nation in regards to having blitzed our resources," said University of Miami marine biologist Jerald Ault.
Ault and others are studying whether putting large tracts of ocean off-limits to fishing in the Keys can help species rebound - and prove a way to help reverse the effects of overfishing worldwide.
Federal and state scientists, along with University of Miami researchers, wrapped up a 20-day study on June 9, after 1,710 dives in the region, surveying fish sizes and abundance, in an effort to determine whether it's working.
Critics assert that it isn't. They say limiting size and catch quantities, not fencing off the seas, will help restore ocean life.
The fierce debate has raged between scientists and anglers for years. Some studies suggest the outcome could mean life or death for not only commercial and sport fishing, but for mass seafood consumption as it exists today.
Florida has the largest contiguous "no-take" zone in the continental U.S. - about 140 square miles are off limits to fishing in and around Dry Tortugas National Park, a cluster of seven sandy islands about 70 miles west off Key West amid the sparkling blue-green waters that teem with tropical marine life. Nearby, another 60 square miles are also off limits.
The region is home to some 300 fish species and lies within a crucial coral reef habitat at the convergence of the Gulf of Mexico, the Caribbean Sea and the Atlantic Ocean.
Fish larvae produced here can be swept on ocean currents as far north as the Carolinas.
Ault fondly calls the area "Florida's Yellowstone," loaded with tropical fish, endangered sea turtles and sharks.
It's been about seven years since the first portion of this no-fishing zone was created in the Florida Keys National Marine Sanctuary.
While Ault and others say there are clear signs of a resurgence - that grouper, snapper and other reef fish are now being found in greater numbers and are growing larger - they acknowledge definitive answers may be years away.
"It's way too early to make those kinds of pronouncements," said James Bohnsack, of the National Oceanic and Atmospheric Administration, who also is working on the study. "The only way we're going to confirm this is to follow it through time." Bohnsack said it could be 15 years before scientific data fully verifies the theory.
But he said the premise is based on simple logic.
Coral reefs serve as crucial breeding grounds for some of the world's most popular fished species. Keeping anglers away, scientists believe, will create havens where fish can feed, grow and spawn, then migrate to areas that have been overfished.
The larger a fish grows, the more eggs it can produce. If anglers continue to snap up all the big ones, eventually, Bohnsack warned, the entire system could collapse.
Overfishing has cut deeply into the world's fish populations.
A 2006 report in the journal Science warned that nearly a third of the world's seafood species have declined by 90 percent or more and all populations of fished species could collapse by 2048 if current fishing and pollution trends continue.
Bohnsack and Ault hope to prove that by closing critical breeding grounds, such a catastrophe can be averted. But others aren't convinced.
Ted Forsgren, executive director of the Coastal Conservation Association Florida - a nonprofit group that represents anglers - said he has seen no indication that fish from the protected areas are replenishing the seas where fishing is allowed.
Forsgren vigorously opposes no-take zones, and says limiting catch size and quantity is a better approach.
"There's evidence that shows that if you create a no-take zone you'll end up with more fish in there, and that's true," Forsgren said. "But we haven't seen any of these no-fishing zones that have provided replenishment to adjacent waters."
A state and federal study released in February on a network of no-fishing zones around California's Channel Islands found that since those preserves were created five years ago, the population and size of spiny lobsters and other species have increased.
Still, the study's findings only "suggest" that since lobsters in the protected areas are growing bigger, it is "likely" they could "spill over" into unprotected areas.
Even so, many in the scientific community insist the concept will pay off.
No-take zones around the world operate under just that theory, although many allow limited fishing for research and indigenous groups.
Australia's Great Barrier Reef Marine Park has the world's largest network of no-take areas, with more than 44,000 square miles off limits to fishing.
The United States' largest no-take marine reserve is a 1,547-square-mile network within Hawaii's remote Papahanaumokuakea Marine National Monument, according to NOAA.
Limited sustenance and research fishing and a few small commercial operations are currently allowed within much of the remainder of the monument's 140,000 square miles, but all commercial fishing there will be phased out by 2011.
Mike Hirshfield, chief scientist at Oceana, a sea life advocacy group, said that if current fishing trends continue without added protections, anglers could fish themselves out of business. He compared reef habitat breeding grounds to investment banks.
"Once you liquidate the capital, you can't live off the interest anymore," he said.