Log found!
Posted by Andrew via Email at 10:40 PM, August 18, 2004
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| (C) Greenpeace |
Yep, there is little in the way of ocean debris that can escape our keen eyes. That is your basic floating log pictured there to the left, and the most exciting thing to happen to us all day long. Ok, it's more of a "plank". Now, I'm using the word "log" (or "plank") here for the benefit of our readers unschooled in the lingo of the tuna fishing industry. In their parlance, something like this is better known as a F. A. D. - that is a "fish aggregating device".
Larger photo
Apparently, anything of decent size floating on the water will attract fish. Logs, garbage, boats, whatever. Why? Well, Roger says that at first the FAD is attractive to the fish because it's something to "visually orient on". I think he means it's just something to look at, and it's a phenomenon I've seen myself. When we stop the ship in water with good visibility, after a short while you can see a few fish swimming around under us.
Now, I know exactly what you're thinking, because it's exactly the same thing I was thinking... If fish gather around under anything that floats, then why don't fishing vessels just sit there and wait for the fish to come to them? Hmm?
But no, it doesn't work like that. You get a few stragglers fairly quickly, but it takes days or weeks to build up a large number of fish. Algae and stuff grows on the FAD. Little fish eat the algae. Then, of course, bigger fish come to eat the little fish, and bigger bigger fish come to eat them. Pretty soon you've got a whole marine community living happily under the log, coconut or discarded refrigerator.
Sometimes fishermen will deploy artificial FADs made from bamboo, plastic or whatever, with lights dangling from the bottom and a transponder to help them find it when they come back later. The larger purse seiner fishing ships also carry a helicopter, which will go look for logs, and tag them with a radio beacon.
Actually, today we saw two logs. Roger (photographer) and Wooly (videographer) jumped in both times with their waterproof gear, and got some nice shots of what was happening underneath. They saw around 300 triggerfish, 100 rainbow runners, a few mahi mahi, a small shark and a bunch of other fish. No tuna, but maybe it was the wrong time of day for them to be near the surface.
-- Andrew
