Their immense size - they are the largest species of fish in the world - doesn't necessarily mean that whale sharks are significantly easier to keep tabs on and study than their smaller relatives. While it has long been recognized that these behemoths, which can measure over 40 feet in length and 35 tons in weight, are plankton-eating filter feeders, much about them remains unknown or has become known only relatively recently.
For example, it was not until the 1996 capture of a female pregnant with 300 pups that scientist were able to conclude definitively that whale sharks are ovoviviparous: their young grow in egg sacs inside the body but are born live. As for their population size, little to nothing is known.
Researchers have, however, established that the pattern of dots and bars on whale sharks' flanks is unique to each animal, like humpback whale flukes or human fingerprints, and that therefore studying photographs of individual whales is a good way to track them - as is attaching satellite tags like the researchers in this video are doing.
| Swimming with a whale shark off the Alabama coast |
Still, the more knowledge the merrier, so scientists were thrilled to see a group of perhaps 100 sharks in the Gulf last week, off the coast of Louisiana in an area that apparently remained untainted by oil from the Deepwater Horizon. Alas, this week came news of three whale sharks swimming in oil just a few miles from the gushing wellhead. "That basically confirms our worst fear: these animals do not know to stay away from the oil,"said Eric Hoffmayer of the University of Southern Mississippi Gulf Coast Research Lab.
That's bad news because, he laconically observed, "Taking mouthfuls of thick oil is not conducive to them surviving."
Noted Ben Raines of the Mobile Press-Register:
That doesn't mean that there will be oil-coated whale shark carcasses along the Gulf coast. If the spill does kill members of the world's largest fish species, we'll likely never know how many. Like other shark species, whale sharks have no swim bladder. When they die, they sink to the bottom, never to be seen again."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 [...]
"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?"
Tags: Animal Anatomy, Animal Research, Animal Science, Conservation, Sharks
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