San Francisco Bay: Return of the harbor porpoise
Marine biologists in the Bay Area have noticed the return of the harbor porpoise ((Phocoena phocoena) to waters underneath the Golden Gate Bridge and around Angel Island, after a decline that began around the time of World War II. The presence of much of the Pacific Fleet in the Bay may have had a large negative effect on apex predators like the harbor porpoise. As with any good mystery in biology, the exact reasons for the disappearance of the harbor porpoise, and the exact reasons for its return, are unknown. Scientists actually know a lot less than most people believe. On the PLUS side, scientists place a lot more importance on actual data than most other folks do.
“We don’t know why they disappeared. … It’s very possible that they just abandoned the place because it became too hard to feed, reproduce and raise their young,” said William Keener, a co-investigator and spokesman with the nonprofit Golden Gate Cetacean Research group.
Then all of a sudden, the porpoises were back.
Some scientists think that the quality of the water in San Francisco Bay, which became MUCH worse in the decades after World War II, but has begun to improve recently, may be implicated. Some think that global warming and the rising temperatures of the ocean may be involved. Other scientists speculate 
that as less freshwater enters the Bay from the Sacramento-San Joaquin River Delta and its tributaries, the Bay becomes more saline. This change may bring more cetacean prey species into San Francisco Bay. Another, larger, marine mammal, the California bottlenose dolphin, has also been observed inside the Bay.
Using what may be the world’s largest wildlife observation station – the entirety of the Golden Gate Bridge itself – Keener and his colleague train their telephoto camera lenses straight down 220 feet off the span’s railings while watching the harbor porpoises hunting and feeding, mating and calving, parenting and just having fun and hanging out.
“Shooting off the bridge allows us to observe them in all aspects of life without disturbing them. They have no idea we’re there,” Keener said.
(At this point, readers of the novel, “So Long, and Thanks for All the Fish” may ask, “Are the scientists so SURE?” )
-Bill at
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