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PRI's Environmental News Magazine

Whale Sharks in the Gulf

Air Date: Week of July 9, 2010

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Scientists still aren’t sure why whale sharks have their distinctive spots. (Photo: Jon Hanson)

The world's largest fish has been spotted swimming through crude oil in the Gulf of Mexico. Host Jeff Young speaks with Bob Hueter, Mote Marine Lab’s Director for Shark Research, about the fate of the gentle giant, the whale shark.

Transcript

YOUNG: Last summer, scientists who study the world’s largest fish were excited to discover a group of a hundred whale sharks feeding in the waters just off the Mississippi delta. This summer, those scientists hope the whale sharks stay well away. Bob Hueter directs the Center for Shark Research at Mote Marine Laboratory in Sarasota, Florida, and tracks the animals as they travel through the Gulf of Mexico.

HUETER: We’re deeply concerned about whale sharks in that area because these are filter-feeding sharks. They come to the surface, especially in the morning hours, and open their enormous 6-foot wide mouths, and just strain the plankton that’s present in the water column near the surface. They’ll do this for hours and hours on end. In that sense they’re not like the other sharks. They’re more like giant cows. And unfortunately we use “sea cow” for manatee, I really think we should’ve used it for the whale shark, but that’s history now.

But as filter feeders at the surface, you don’t have to be a shark biologist to see how having oil floating on the surface would be a huge problem. And these sharks have a straining device, have a filter pad, in their throats, that traps food, passes food back to the back of the throat where it’s swallowed and then pass water through so they can breathe. So as oil comes into the mouth, it can get trapped on this filter, which kind of resembles the filter in your air conditioner at home, and clog that filter up. Not only then would they not be able to feed, but it’s very possible that they would have troubles breathing.

YOUNG: You recently had a report of a group of what, 10 or so just off your coast there around Sarasota?

HUETER: That’s correct. So we’ve been looking at the distribution of whale sharks in the area and we’ve been noticing that more and more are showing up on the eastern side right here off the Florida Gulf coast, which is highly unusual. We’ve had whale sharks here continuously for six weeks now following about a month after the blow out of the Deepwater Horizon well.

YOUNG: So, maybe they’re sensing the oil and fleeing it?

HUETER: Well, we certainly hope so because oil and whale sharks don’t mix.

YOUNG: You know, we don’t have the benefit of pictures here on radio unfortunately, but describe for us, what does a whale shark look like when you come up on one in the water?

HUETER: Well, whale sharks are the largest fish that have ever existed. They can get to be as long as 45 feet; their background color is like a deep brown or even almost a black, with light-colored polka dots all over them. Although people have known about whale sharks for centuries, they’re greatly mysterious to us.

We don’t know where they give birth to their young, we don’t know where they mate, we don’t know a lot of aspects of their life history, and whale sharks are just absolutely benign creatures. They don’t have a bad bone in their bodies. And they just want to feed. They’re very tolerant of people being around them. It’s almost a religious experience to swim with the whale sharks, to be with an animal that large that’s so powerful and yet so gentle.

YOUNG: And, as part of your tagging program I notice you named one of them Sara, obviously after Sarasota, and she might be ready to give birth, is that right?


Scientists still aren’t sure why whale sharks have their distinctive spots. (Photo: Jon Hanson)

HUETER: She’s just coming into the size of being reproductively mature, and she looked like she was a little pudgy, so we were very excited to get a tag on her to be able to track her. For a select number, about 35 animals, we have used a satellite tag, which transmits to us essentially every day. The information comes down to us by email right to the laboratory. That’s the information, that’s the kind of tag that we have on Sara.

YOUNG: That’s so cool- you basically get an email from Sara.

HUETER: That’s right, Sara phones home just about every day. Just like a good college student.

YOUNG: And, what are you learning about her activity so far?

HUETER: Well she has been off the Florida Gulf Coast for the last month or so and she went south first, then did sort of a U-Turn, and has actually moved up in the north, up in the what we call the “big bend area” of Florida. Staying about 40-50 miles offshore at this point. Now that brings her into closer proximity with the distribution of oil, so we’re very concerned and we’re watching her movements to see if she turns back when she encounters the oil.

YOUNG: What’s your hunch about how this is going to play out for whale sharks in the Gulf?

HUETER: I’ll tell you that once this thing started, I felt such a sense of doom that I was really depressed about it, but as time has gone on, as I reach back and go to that optimistic place that knows that nature can rebound, I am hopeful that the whale sharks will sustain themselves through this disaster in the Gulf and will find a way to stay away from the oil and do other things until the oil is dispersed and they can get back to their normal routines.

YOUNG: Dr. Bob Hueter at the Mote Marine Lab in Sarasota Florida, thank you very much.

HUETER: Thank you.

YOUNG: You can track Sara and other whale sharks in the Gulf at our website,
LOE dot org.

 

Links

MOTE marine lab’s shark research center

Gulf Coast Research Lab’s whale shark program

 

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