Saturday, 28 June 2008

Satellite Tracking of Thresher Sharks.

When I was home last, I went out fishing with my good friend Scott "Scootch" Aalbers. He's a research marine biologist, and his latest project involves the catching, tagging and releasing of Thresher Sharks. His objectives:
  • 1. Estimate a catch-and-release mortality rate for thresher sharks in the Southern California recreational fishery.
  • 2. Analyze the physiological indicators of capture stress (e.g., blood and tissue biochemistry, stress proteins).
  • 3. Investigate alternative gear types and methods (e.g., circle hooks, teasers, break-away tackle) to reduce capture stress and mortality.
  • 4. Develop a strong outreach program that uses public educational seminars and popular literature to discuss best fishing practices.
I was lucky to be asked aboard his research vessel the Fish Tale to take part in his study. At dawn, we steamed out to the ten mile bank and started dragging rapala baits. After a few hours burning diesel, we hooked up with an 11 foot male thresher shark, and that's where I came in. I was handed the pole and given my instructions: "Reel."

Now, Scootch has been on the water all his life. He's got seawater in his veins. So he could have told me to keep my knees bent and my back straight. He could have told me to take line while the boat goes down a wave, and just hold on when it goes up a wave. He could have told me any number of things that would have shortened the fight. But he didn't. And that's because he wanted me to fight the shark like a novice, day-boat passenger. By the way, if you've never fought an 11 foot thresher shark, they're strong. Way stronger than you. In fact, it took me 80 minutes to land that sucker, and that was the whole point of the exercise.

You see, Alopiidae attack their prey with their long, scythe-like tails so they're usually tail-hooked when caught. That means they have all the leverage working in their favor. It also means that they get dragged to the boat backwards. That's not good for sharks and it's why so many die, even when released.

Once we got the beast to the rail, Scootch inserted a satellite tag, took some flesh and blood samples and released him back into the deep. We waited a week for the satellite tag to release itself, pop up and "phone home." When it did, it appeard about thirty miles north of where we released the shark. Much too far for the animal to have drifted. That means it lived. Hooray!

The image below is from the sat-tag tracking website showing where the tag was found. I gotta say, I love this stuff. There's something cool going on when you're doing a mashup of "Old Man and the Sea" and "Wargames" And Scootch gets to do this kind of thing every day. He's the richest man I know.

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