“This might have implications for two or three years down the road,” he said.

Some fishermen are unwilling to wait that long for their catch to improve. The world of crabbers is tight-knit, and several fishermen in the Florida Keys and Everglades City pointed to Mr. Barnhill, the third-generation crabber in Pine Island, as a symbol of the pain they have suffered. Mr. Barnhill sold his boat last summer and more than 8,000 traps this summer; he has turned his fish house into an ice house, to supply bagged ice commercially.

“I can’t survive in the fishing business,” he said. “I used to run 50 miles one way to go crabbing, and there ain’t crabs there now. There’s crabs 150 miles out, but you can’t do that in one day.”

Stone crab claws must be cooked dockside on the same day they are caught or they will spoil, which is why the robust season this year north of Tampa, away from the red tide, means little to fishermen who cannot get there and back in time on their boats. (Fishermen remove claws from live crabs and then return the animals to the water to regrow them. Scientists and even fishermen admit the process is stressful for the creatures, which don’t always recover.)

Mr. Barnhill said his father also sold his traps this year. “It’s not just an average, ordinary red tide. There’s something a lot bigger and way worse,” he said, noting mullet and other fish have also been killed off. “There’s a lot of poor fishermen that are starving to death right now, and there ain’t nobody lifting a hand to try to help.”

Mr. Sawitz, the owner of Joe’s, said the restaurant routinely lends money to crabbers who work for them at Ernest Hamilton Stone Crab in Everglades City and Keys Fisheries in Marathon, helping to fix their boats and replace broken engines before the season begins in October. His fishermen catch about 20 percent of all of the stone crab caught in the state each season, Mr. Sawitz said.