Reeling in Nature's Mysteries -- Chum Salmon, Japan
Ah, mouth-watering salmon! Yet not much is known about this treat aside from what we see on the dinner table. The Darwin team decided to join a number of surveys to find out more. Back in their natal streams, males fight over females. Does the loser simply swim away? No! "He" turns into a "she"! During the act of spawning, the pair's hearts stop ... but it's not out of love! And while in the open ocean, these fish can reach depths approaching the deep sea. Why? The reason is ... unfathomable!