By Ben Raines
(See undersea video at original article)
Last week, scientists cheered the discovery of one of the largest groups of whale sharks ever sighted in the northern Gulf of Mexico — about 100 animals feeding on the surface over a deepwater feature off Louisiana called the Ewing Bank.
This week’s report: Three whale sharks swimming in heavy oil four miles from the gushing Deepwater Horizon wellhead.
“Our worst fears are realized. They are not avoiding the spill area,” said Eric Hoffmayer, the University of Southern Mississippi scientist who found the large aggregation last week. “Those animals are going to succumb. Taking mouthfuls of oil is not good. It is not the toxicity that will kill them. It’s that oil is going to be sticking to their gills and everything else.”
Whale sharks, the largest fish on earth, feed by filtering plankton and tiny fish from the water through sieve-like mechanisms in their mouths.
“Based on all the information I’m getting, they are doing the normal things regardless of the oil. The idea that sharks have these evolved senses that will protect them — well, they haven’t evolved to detect oil,” Hoffmayer said.
He tagged whale sharks on the Ewing Bank in June of last year. The satellite trackers showed that some of the animals spent that July migrating hundreds of miles toward the Alabama coast and Florida Panhandle. If they follow the same route this year, it would carry them straight through the heart of the spill.
The Press-Register videotaped Hoffmayer, who works from the USM Gulf Coast Research Laboratory in Ocean Springs, as he tagged a whale shark about six miles off Orange Beach last August. He said little is known about their migration habits and life histories. For instance, scientists don’t know how many of the sharks call the Gulf of Mexico home.
The best way to follow their wanderings is using pictures of the spots and bars on their sides. Each animal’s patterning is as distinctive as a human fingerprint.
“Last year we had two sighted off Florida and Alabama that were from Honduras and Belize,” Hoffmayer said. “That means these oil impacts are not only for the Gulf population, but for the Caribbean and maybe even further. The implications are pretty big here.”
He said that high Gulf temperatures and the position of the offshore Loop Current mean conditions this year are similar to those that drew the sharks to the area last summer.
“If that migration pattern holds true this year, the sharks will have to travel through the oil to get to Alabama,” Hoffmayer said. “That’s a serious concern. These guys are surface feeders. They swim at the surface with their mouths open. Will they be ingesting oil?”
Hoffmayer said that there will be no way to determine the spill-related toll on the overall population. Like all sharks, whale sharks do not float to the surface when they die.
“They are dense animals,” Hoffmayer said. “They don’t have a swim bladder. They have this liver. When they succumb, they are going to sink to the bottom.”
Hoffmayer said he has already had a few reports of whale sharks off Pensacola.
He said he’s thus far been unable to secure funding to get more of the $4,000 satellite tags, which provide the only insight into the movements and habits of the whale sharks. This year, they could provide the only record of their exposure to oil.
“We’re going to miss our window if we don’t get our tags out soon,” Hoffmayer said. “These animals are in peril.”
Whale shark sightings should be reported to Hoffmayer at 228-872-4257. More information is available at the Gulf Coast Research Laboratory’s University of Southern Mississippi website.