Like the swallows of Capistrano, the harbor porpoises of San Francisco Bay have decided to come back. The question everyone is asking is why now after all these years? You can research it and study the phenomena but the fact is quite simple: They hadn't come back because they hadn't wanted to, until now.
In the olden days of coal mining, the men would take canaries into the mine shaft with them. If the birds keeled over dead, the miners knew the quality of the air was dangerous. It seems that now, harbor porpoises (from the dolphin family) are doing the same for the waters of the bay surrounding San Francisco. After several years of the Clean Water Act being in effect, the waters are cleaner than they have been in years, and the porpoises have returned to play.
Opponents of the Clean Water Act would contend that it all is just unnecessary government meddling, but often that opinion is merely promoted by those with a financial vested interest in deregulation or no regulation at all. The dolphins have no political clout, but they know clean water when they see it.
60 Years After Leaving, Porpoises Again Play In SF Bay
NPR
Something that has been missing from San Francisco Bay since World War II appears to be making a comeback: Harbor porpoises are showing up in growing numbers, and researchers are trying to understand why they're returning.
The walkway across the Golden Gate Bridge is almost always packed with people taking photos. But Bill Keener isn't here for snapshots of the stunning views. He's aiming his massive telephoto lens at a dark shape in the water 200 feet below.
"There's a porpoise right there, coming very, very close," he says. "Here's a mother and calf coming straight at us." Keener is with Golden Gate Cetacean Research, a nonprofit group focused on studying local porpoises, whales and dolphins.
