Wild Things: Life as We Know It

Wolves, hibernating animals, spitting cobras and more

(Jim and Jamie Dutcher / NGS Image Collection)

How Fish Recycle

So, how many fish are in the sea?
(Maura McCarthy)
So, how many fish are in the sea? Scientists led by the University of Exeter in England have a new answer: about two billion tons. The estimate comes from a study of how ocean fish absorb dissolved calcium and convert it into calcium carbonate, which they dispose of in granules called "gut rocks." Snails, crabs and other creatures build shells out of the fish excretions.

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