Monday, August 09, 2010

When the world's biggest fish poops

Biologists are strange, and that really shows up when they start thinking and talking about poop. Witness biologist Alistair Dove talking about the lure of dipping a net to sample the poop of a whale shark, the world's biggest fish:

“Nobody has done this analysis yet,” said Dove, who referenced a scene from Jurassic Park, when Laura Dern’s character is ecstatic at the chance to poke through a pile of dinosaur droppings. “It could be a literal gold mine.”

Why is he so excited about a very large poop? Because it's a chance to learn a lot about a very interesting fish. It's hard to know what goes on inside a wild animal, and poop is one of the best ways to find out (without harming the animal, of course). According to Wired Science:

With a fresh sample, researchers could perform high-powered chemical and genetic analyses of its contents, learning in precise detail what these threatened giants consume in the wild. Dove is especially curious about their digestion. In aquariums they thrive on a relatively spartan diet, suggesting high efficiency in converting food. But a colleague on the research trip had observed whale shark defecation first-hand, and said their food was barely digested.

“He says it comes out looking much the same as when it goes in,” said Dove. “Maybe they’re efficient when food is scarce, but when they find a good patch, their efficiency drops in favor of gluttony. They’re eating so much, they just push it through.”

That colleague happened to find a group of whale sharks feeding — a spectacular affair, in which scores swim in a synchronized frenzy, sucking up water and food, and discharging wastes on the spot.

“Pooping events may play important oceanographic roles,” concentrating surface nutrients and delivering them to the water column and seafloor, said Dove. Scientists now think that baleen whales perform just such a task, and may be vital to nutrient circulation in the ocean.

Dove estimated the main plume in the photograph to be 30 feet long and 20 feet wide, and the smaller about 8 feet by 10 feet. If it’s three feet thick, the nutrient slurry would have a volume of 2,000 cubic feet. “Imagine you’ve got a big aggregation, dozens or hundreds of whale sharks, doing this all at the same time. That’s a lot of nutrients,” he said. Dove hopes to collect samples from just such a group.

1 comment:

patric douglas said...

To this may I add "When the worlds most predatory fish poops".

This was shot quite a few years ago, first time we had ever seen a white shark evacuate: