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If you have sailed on SF Bay in the past few years, you have no doubt notices the increase of Harbor Porpoises
gathering just outside the Golden Gate in great abundance. Also inside the Bay itself, a local herd seems to frequent
Raccoon Straits as well, numbering in the 20's. We have even noticed a smaller herd at the edge of Hunters Point with
great frequency.
Heck, Otters have even started making an appearance at the San Rafael Canal
© David Wells
Many of you have been curious as to why the recent influx? It seems to have also caught the attention of
Bill Keener from Golden Gate Cetacean Research, a nonprofit group focused on studying local porpoises, whales and dolphins.
The big question, though, is why harbor porpoises disappeared in the first place. Keener says the Bay has always been porpoise habitat. Sightings were common until the 1930s.
"We don't really have reports from around World War II, and there were a lot of things going on during World War II that could have caused [the decline]," he says.
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 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.
"I remember coming across the Bay Bridge when I was very young, and it would just smell," Keener says. "It would stink."
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.
"Over 60 years, we're talking about a number of generations of porpoises," Stern says. "So it's quite likely that San Francisco Bay as a habitat was out of the institutional memory."
"We don't really have reports from around World War II, and there were a lot of things going on during World War II that could have caused [the decline]," he says.
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 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.
"I remember coming across the Bay Bridge when I was very young, and it would just smell," Keener says. "It would stink."
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.
"Over 60 years, we're talking about a number of generations of porpoises," Stern says. "So it's quite likely that San Francisco Bay as a habitat was out of the institutional memory."
Check out the full article at NPR Radio