Mass Die-Off of Sharks Along Gulf Coast of Florida a Mystery

Decaying dead sharks covered half a mile of Florida beaches on the Gulf of Mexico on Wednesday, puzzling biologists who could not explain the mass deaths.

“I’ve never seen anything like this,” said Dr. Enric Cortes, a biologist for the National Marine Fisheries Service. “Mass mortalities in sharks are very unusual.”

Cortes said the mysterious deaths probably occurred over the weekend. About 85% of the sharks were black-tips and the rest were Atlantic sharp-nose, he said. Most were juveniles 3 1/2 to 4 feet long.

A U.S. Fish and Wildlife Service researcher reported that some of the fish appeared to be bleeding from the nostrils and gills, something biologists said could have been caused by a viral infection.

Cortes said he saw no blood on the 100-plus carcasses he inspected Tuesday, nor were there any signs the sharks had been injured by fishing nets or long-line gear.

An algae bloom known as red tide has been reported in the area, but it would have killed other fishes and sea life, and no other species was dead, Cortes said.

The sharks may have died from a low level of oxygen in the shallow waters, he speculated.

Biologists collected tissue samples to send to the Florida Marine Research Institute in St. Petersburg to check for signs of red tide.

A red tide can kill fish and cause respiratory irritations and watery eyes in humans.