I spent many days in the 1980s and 90s leading trips off the coast of Northern California whale watching and out to the Farallon Islands. And as we went under the Golden Gate Bridge and out to sea, I would encourage folks to keep their eyes out for a very small porpoise — the harbor porpoise. Only six feet long at most, they are one of the smallest cetaceans of the 75 species of whales, dolphins and porpoises. And as the name indicates they are found in shallow water, usually less than 150 feet. They are confined to the cool waters of the Northern Hemisphere and certainly our local ocean waters are cool and shallow.
Harbor porpoises are not very showy. They usually do not bow ride vessels nor leap out of the water. What you see is a small brown triangular dorsal fin cutting quickly through the waves. Nevertheless, it is always thrilling to see a porpoise. Aristotle first recognized they were air breathing mammals and not fish when he named them “Porcus pisces” which literally means “pig fish.”
In the last several years these porpoises have moved east of the Bridge into San Francisco Bay much to the delight of nature lovers. In times of environmental degradation, it is pleasing to see an animal returning on its own volition to its original habitat. We aren’t exactly sure what changes there are in San Francisco Bay to encourage this. It may be that environmental regulations, which have limited industrial and domestic discharges into the Bay, have created a healthier situation. Or it may be large-scale changes in the ocean environment that have resulted in more biological productivity in the Bay. And it is true that some species of fish such as herring have increased in recent years and these harbor porpoises feed on small schooling fish.
At any rate, these porpoises are easy to see from Fort Baker in Marin County, the Financial District, Treasure Island, Angel Island and especially from the walkway on the Golden Gate Bridge. What a delight.