An unprecedented number of bottlenose dolphins have died this year after gobbling baited hooks or lures, or becoming entangled with fishing line.
So far, encounters with recreational fishing gear killed 13 dolphins across the state this year compared with four during all of 2005.
Scientists worry it could grow worse.
"For a dolphin to put its head out of the water like Flipper is not a natural behavior," said Stacey Carlson, dolphin conservation coordinator with the National Marine Fisheries Service in St. Petersburg. "We're not sure of the cause of this."
The mammals may be associating anglers with a free meal. Or they may be more desperate for food after red tide depleted stocks of their normal prey.
Scientists have observed dolphins snatching baited hooks and hooked fish in waters around the Skyway Pier. They've discovered lures in dead dolphins on the state's west and east coasts.
Wild dolphins don't naturally steal bait from a hook, Carlson said. Normally, they eat small fish such as mullet, mackerel or pinfish.
Most of the dolphin deaths have been concentrated in Sarasota Bay and the Indian River Lagoon on the East Coast. Two were near Clearwater, the closest any dead dolphins were found to Tampa Bay.
In the Sarasota area, three adult dolphins died with hooks or lures lodged between their lungs and blowholes. A calf died when fishing line wrapped around its tail, nearly severing it.
A treble-hooked fishing lure in a fifth dolphin's mouth may have contributed to its death, said Randall Wells, director of the Center for Marine Mammal and Sea Turtle Research at Mote Marine Laboratory in Sarasota.
"It's a horrible way to die," said Wells, who has observed dolphins in Sarasota Bay for 36 years. "Some of those were animals we've known since they were born."
The number of deaths amounts to about 3 percent of the dolphins that permanently live in and near Sarasota Bay. Add that to the normal death rate of about 5 percent a year, and the population can't support the loss.
"They're not making enough babies to make up for that," Wells said.
In Sarasota Bay, dolphins might be looking to humans for food after the worst red tide in three decades seriously reduced their food supply.
"We can speculate. There was a severe decline in their normal prey. If they're more hungry, they might have a level of desperation," Wells said.
But there was no red tide outbreak to deplete fish in the Indian River, Carlson said.
Carlson and other researchers from the National Oceanic and Atmospheric Administration spent more than 100 hours this year observing and interviewing anglers at the southern Skyway Pier.
They saw dolphins eating squid, shrimp, live and cut bait from hooks and sometimes eating a hooked fish. Some managed to eat the fish without getting hooked.
They also saw people feeding dolphins intentionally, which is illegal, and unintentionally by dumping leftover bait into the water.
"This encourages dolphins to hang around people," Carlson said.
That's why NOAA is making an effort to warn people of the harm feeding the dolphins can do.
Also, dolphins that learn to associate humans with an easy meal may teach calves to do the same, reinforcing the dangerous behavior for the next generation.
"If the feeding stops, the animals will not go hungry," Carlson said.
HOW TO HELP:
Ways to help protect dolphins:
•Never feed wild dolphins: It is against federal law and is harmful to the dolphins.
•Avoid tossing leftover bait to dolphins if they are nearby. Take it home to freeze or give it to another fisherman.
•Avoid fishing in an area where dolphins are actively feeding, and change locations if they take an interest in your bait or hooked fish.
•Use hooks that will corrode, and avoid stainless steel hooks.
•Stow used fishing line and dispose of it at the dock. Dolphins and sea turtles can be entangled in the discarded line.