Narrator: That's Elizabeth Brainerd, a biologist and puffer fish expert at Brown University. Brainerd: And they do that anywhere 10 or 15 times, pump, pump, pump, pump, pump, pump, until they ...

There are over 120 species of puffer fish, and 22 different kinds are approved by the Japanese government for use in restaurants. But one is more prized, and more poisonous, than the others ...