Nightly News   |  August 16, 2010

Tracking whale sharks in the oil leak zone

With millions of gallons of oil remaining in Gulf waters, scientists believe whale sharks could be the key to understanding if the entire ecosystem is in jeopardy. NBC's Jeff Corwin reports.

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This content comes from a Full-Text Transcript of the program.

BRIAN WILLIAMS, anchor: As promised, we want to go back to the Gulf of Mexico now for a close-up look at how scientists are trying to measure the oil leak's impact on wildlife. For one thing, they're checking on the health of a giant species that could offer some broader insight. Our own Jeff Corwin traveled to the Ewing Bank off the coast of Louisiana .

Mr. JEFF CORWIN (NBC News Wildlife and Science Expert): It's a boat ride a top speed for Eric Hoffmayer of the Gulf Coast Research Lab , searching for the largest fish on Earth , the whale shark , elusive and shy filter feeders with massive mouths -- easy targets for oil.

Mr. ERIC HOFFMAYER: This is the whale shark research group. Do you copy?

Mr. CORWIN: Finding them would be next to impossible if it were not for Eric 's eyes in the sky, spotter planes already in the air, scanning hundreds

of miles of the Gulf of Mexico. His mission: tracking and investigating the condition of whale sharks feeding in the oil leak zone.

Offscreen Voice: We've got two whale sharks .

Mr. CORWIN: Five anxious hours later, and 60 miles off the coast of Louisiana ...

Unidentified Woman: Copy on the whale sharks . Please repeat the coordinates.

Mr. CORWIN: ...we finally get good news from the sky.

Mr. HOFFMAYER: We're heading your way.

Mr. CORWIN: Racing to hook up with our circling planes, it's time to tag these fish in order to keep constant track of their movement. Swimming with them is the only way to do it. These gentle giant fish, which can grow up to 40 feet in length, feed almost exclusively on plankton. Eric and I attach a satellite tag to the first shark. The trailing beacon transmits a signal any time it comes to the surface. A second pop-up tag tracks the fish's depth and temperature. If the shark ingests oil and dies it will likely sink to the bottom. In order to determine the health of this shark, a tissue sample is carefully taken from its fin. Now that the whale shark has been fitted with transmitters, we'll now know if it's coming into harm's way. Photos taken just weeks ago show whale sharks swimming in oil. Scientists now believe these fish later died. The challenge now is to find the others.

Mr. HOFFMAYER: These animals are extremely important. They're sort of an indicator of sentinel species in this Gulf of Mexico ecosystem, and they're feeding at the base of the food chain.

Mr. CORWIN: With millions of gallons of oil remaining in gulf waters, scientists like Eric Hoffmayer believe these sharks, like canaries in the coal mine, could be key to understanding if the entire ecosystem is still in jeopardy. Jeff Corwin , NBC News , the Gulf of Mexico .