S1, E6: The rarest and smallest of all the worlds marine dolphins exist in New Zealand: In the North Island the Mauis dolphin, and in the South, the Hectors. And the single, greatest threat to the survival of the remaining 7,000 dolphins is entirely of mans making: fishing. The use of gill nets, a wall of death for everything caught in it, has caused the New Zealand government to introduce a ban in order to save the Hectors dolphin.