San Francisco Bay is the most invaded aquatic region on Earth, with more than half its fish and most of its bottom-dwelling organisms representing non-native species, according to a new report released by the Nature Conservancy.If you looked at the Bay, you would never know the difference, however. We can see floating junk, and discoloration, and fire, but for the most part, it's hard to judge the health of the ocean by eye-balling the surface the way we might survey a forest. Consequently, it's easy to ignore the ecologies of our oceans, as Callum Roberts points out in his book, The Unnatural History of the Sea. Perhaps we should all go scuba diving now and again to (re)acquaint ourselves with that vast other world--not that I would know that Chinese mitten crabs don't belong in the Bay in the first place.
Asian clams, Chinese mitten crabs, Amur River clams, New Zealand carnivorous sea slugs, Black Sea jellyfish and Japanese gobies are just a few of the exotics that have ended up in San Francisco Bay, usually transported in ships' ballast water.