Diver Jerald Ault measures a red grouper during a dive. Researchers are studying whether prohibiting fishing in large tracts of ocean in the Florida Keys can help species rebound and prove a way to help reverse the effects of overfishing worldwide.

Dry Tortugas National Park, Fla. ? 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.