Harbor Porpoises Return to San Francisco Bay

For the first time in over sixty years, to the delight of both researchers and onlookers, harbor porpoises are returning to the San Francisco Bay. Experts are now working to discover why the ‘puffing pigs’ as they are called due to their pig-like exhalations, are returning to the Golden Gate Bridge area.

Until the 1930s, the bay was filled with the small porpoises. During World War II, San Francisco became a major shipyard, and with the building came immeasurable pollution. Reports from that period are scarce, but researchers have a few guesses.

For one, the bay became a wartime port. Filled with construction and dozens of ships, the area proved disturbing and often dangerous for the porpoises. The Navy actually placed a seven-mile long net across the opening of the bay to deter Japanese submarines, and the waters beyond the Golden Gate were laced with hundreds of mines.

Bill Keener of Golden Gate Cetacean Research is studying he porpoises’ return. He said that while the war-related disturbances are likely causes for the porpoises’ departure, there was another big change that could have driven them off: water quality.

According to Keener, the water in the bay during the 50s and 60s was unbelievable polluted. He added that raw sewage would flow right into the bay. In 1972, the Clean Water Act was passed. Slowly, water quality in the area began to improve, and many inhabitants gradually made their way back. San Francisco State University whale researcher Jonathan Stern said the porpoises probably needed to rediscover the bay.

“Over 60 years, we’re talking about a number of generations of porpoises,” he explained. “So it’s quite likely that San Francisco Bay as a habitat was out of the institutional memory.” He added, “It’s one of those very good-news environmental stories. And it’s in our backyard. It gives one hope.”


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