Harbor porpoises are being seen more and more in the San Francisco Bay for the first time in about 60 years, and researchers are trying to understand why they’re returning.
Researchers and onlookers on the Golden Gate Bridge are seeing the porpoises in number, and snapping photos of the “puffing pigs” — as they are referred to by old-time sailors who’ve heard their exhalations.
Why Did They Disappear 60 Years Ago?
But first there’s the question of why they disappeared in the first place. Sightings were common until the 1930s, and the porpoises — averaging five feet long, smaller than most porpoises — were last seen in number during World War II, when San Francisco was a major ship-making hub. With ship building comes pollution, one of many reasons that could account for the porpoises’ departure.
San Francisco Bay became a wartime port. It was a major ship-building center. One newsreel reported that 14 warships at one time sailed under the Golden Gate Bridge. And the Navy strung a seven-mile-long net underwater across the opening of the bay to keep out Japanese submarines. Hundreds of mines were planted in the waters outside the Golden Gate.
Keener (with Golden Gate Cetacean Research) says all of this certainly would have disturbed the porpoises. But there’s a bigger change that may have driven them away: water quality.
The bay waters today are a far cry from those of the 1950s and ’60s. As the region boomed, so did water pollution. Keener says raw sewage used to flow right into the bay.
Water Quality Improved After Passage Of The Clean Water Act
After the Clean Water Act was passed in 1972, the bay’s water quality began to improve. But it took time for the food web to come back. San Francisco State University whale researcher Jonathan Stern says maybe the porpoises had to rediscover the bay. But now that they are back, the tourists strolling on the Golden Gate Bridge are thrilled.
What a great story, one of the rare feel-good stories in the news of the environment these days. Let’s try to ensure that these shy creatures stay around.
Photo Credit:Erik Christensen, Porkeri