(Sacramento Bee)
This story is taken from Sacbee / -- Root
San Francisco marine biologists ponder the return of the harbor porpoise
Special to The Bee
PUBLISHED SUNDAY, APR. 22, 2012
SAN FRANCISCO – At the height of World War II, the San Francisco Bay was a true Navy town through and through.
As home port to much of the Pacific Fleet, the place was packed with uniformed sailors and their warships – aircraft carriers, battleships, destroyers and submarines included.
With the nation busy fighting a war, the kinetic pace of the place had a profound impact on the wildlife that called the bay home, marine biologists say. So-called apex predators such as the harbor porpoise were seen less and less.
"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.
Local marine biologists began noticing the presence of the shy creatures inside the bay a few years ago, Keener said. By the fall of 2009, members of his group were regularly observing them underneath the Golden Gate Bridge and around the Angel Island area.
Scientists conjecture that bay water quality may have had something to do with the disappearance. If anything, it got profoundly worse in the decades after the war, but it's started to improve in recent years.
Others have theorized that global warming and rising sea temperatures are the reason for the shift.
And yet others say that as less freshwater comes downstream from the Sacramento-San Joaquin River Delta and its tributaries, the bay holds a greater percentage of saltwater. Such a change could mean more cetacean prey species inside bay waters. According to Keener, at least one other larger marine mammal has been spotted inside bay waters: the California bottlenose dolphin.
Now, more than 65 years after the war, the exact reason that harbor porpoises have returned remains a mystery.
Andrew Gunther, project leader of the 2011 State of the Bay Report for the San Francisco Estuary Partnership – a coalition of resource agencies, nonprofits, citizens and scientists – says that marine biologists are studying the possible link between the bay's improved water quality and the presence of the smaller fish species that may be attracting apex predators.
"We have to be careful to guard against making premature scientific assessments here," Gunther said. "The increased presence of these species is not necessarily good or bad – it's just different."
Gunther noted that the bay's water quality in recent years has generally improved – with some exceptions – due to increased efforts to curb or stop upstream pollutants, the flow of sediments, and the renewal of many of the wetlands that once largely ringed the bay and which acted as a giant filter of downstream runoff.
But, Gunther cautioned, only through long-term research will scientists come to know what brought the harbor porpoise back.
"With those caveats, I will say that I'm happy to see apex predators living and reproducing again inside the bay," Gunther said.
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.
As research continues into the return of the harbor porpoises and other apex predators, one Sacramento area man said he is excited about their presence.
Cameron Widrig, a 20-year Eeastern Seaboard commercial fisherman, said that he was walking near the Sacramento River in the Shore Park neighborhood last November when he heard some strange but familiar sounds – the signature huffing and puffing breath sounds that harbor porpoises make.
"At first I just thought I was hearing things but then I spotted them in the late afternoon sun. There were three of them traveling together," said Widrig, who these days fishes off the waters of northwestern Canada and in the Gulf of Alaska several months a year.
"I honestly wouldn't have ever expected them this far up the Delta, but it was great to see them. I think it's extremely encouraging that they're back and seemingly doing well in the bay," he said.
ONLINE RESOURCES
• To learn more about the Golden Gate Cetacean Research group, go to: www.ggcetacean.org/" target="_blank">http://www.ggcetacean.org/
• To read the 2011 State of the Bay report from the San Francisco Estuary Partnership, go to: www.sfestuary.org/" target="_blank">http://www.sfestuary.org/
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