The Nature Conservancy report calls San Francisco Bay the "most invaded aquatic region on Earth."
Non-native species like Asian clam, Chinese mitten crabs and New Zealand carnivorous sea slugs hitch rides in the ballast water of ships. That water, and those creatures all get dumped here.
The report found San Francisco Bay seems to have more invaders than any place else on Earth -- 85 different species in all. Most of them are harmful to the native fish.
