Oil-covered pelicans quickly became the heart-wrenching poster children for the BP oil spill, now nearly 80 days old and still festering like a cancer in the Gulf of Mexico.
Dolphins also have perished. Bluefin tuna have seen critical spawning grounds compromised. Sea turtles have been cooked alive by cleanup crews trying to burn surface oil.
Now it's feared that another of nature's iconic marine creatures -- the whale shark, which is the world's largest fish -- will soon be included on a checklist of spill victims long enough to fill afield guide.
Sylvia Earle, an explorer-in-residence at National Geographic, agreed with the assessment that many of the more than 100 whale sharks she and other scientists encountered recently during an expedition 70 miles off Louisiana might be "on death row" because much of their historic feeding habitat is closer to shore, within the spill zone.
Whale sharks, long-distance travelers that can measure 40 feet, were once harvested globally. They're classified as "vulnerable," one step up from "endangered" on a red list published by the International Union for Conservation of Nature.
Little is known about migration patterns of whale sharks that utilize the Gulf of Mexico. But some are believed to help support recreational diving industries off Belize and elsewhere in the Caribbean.
What is known is that these gentle giants are filter-feeders who spend much of their time skimming for plankton and small fishes at or near the surface. Unfortunately, this is where spilled oil tends to gather, so the future looks bleak for whale sharks unable to steer clear of now-tarnished areas, such as the Mississippi River Delta, in which they've feed for perhaps millions of years.
Dr. Eric Hoffmayer, a scientist with the University of Southern Mississippi's Gulf Coast Research Laboratory, says at least five whale sharks have been spotted within 20 miles of the spill area. The number might be much greater were it not for boating and fishing restrictions that have limited the number of people who typically report such sightings.
Hoffmayer
tagged four of the whale sharks sighted during the two-day excursion
with Earle. If he can secure funding he hopes to tag several others so
he can monitor their movements and better assess how the population is
being affected."Based on the physical characteristics of the oil," he said, "ingesting it would lead to the gills being covered, which would most likely result in the shark suffocating."
Hoffmayer does not know whether any whale sharks have succumbed to oil ingestion or how long it would take for a whale shark feeding in the spill zone to perish.
He added that it will be impossible to determine the spill's impact without a more extensive tagging effort because whale sharks, like all species of sharks, are negatively buoyant and will sink to the bottom once they die.
"These are questions we just can't answer right now and that's why it's so key that we tag more animals," he said. "Then if the animals move into the spill area at least we know for sure what the outcome will be."
-- Bottom image courtesy of Mark Christy via Gulf Goast Research Lab
-- Editor's note: This post also appears on Pete Thomas' GrindTV.com Outdoors blog
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