Porpoises Return to San Francisco Bay
By OurSausalito.com Events Editor Annamarie Roger
Harbor Porpoises have been spotted in the San Francisco Bay Area for the first time in 65 years.
Why? The Golden Gate Cetacean Research team has several hypotheses. One being that porpoises might have returned now that sewage treatment has become commonplace and the fish in the Bay that porpoises feed upon are healthier. The Bay water is in fact cleaner than it was in the 1940’s, the last decade that porpoises were spotted in the Bay.
Scientists attribute the porpoises’ dissappearance from the Bay to a combination of increasing ship traffic and the installation of the underwater steel net in WWII that reached from Sausalito to San Francisco. The net was initially intended to keep out enemy submarines, however it also drove away the Harbor Porpoises. Once the net was lifted in 1945, the porpoises were kept away by the Bay’s traffic and pollution.
To identify the exact causes of the porpoises’returns, marine mammal researchers with the Harbor Porpoise Project are collecting observations and images of the Harbor Porpoises. They hope to track their journeys, behavior patterns, and find answers to their questions.
The majority of pictures of porpoises were photographed from Cavallo Point, Marin County, and the Golden Gate Bridge. From far away locations, it can be difficult to identify specific porpoises.
Nevertheless, scientists are able to compare scratches, scars, and color patterns to distinguish one porpoise from another. Their data is becoming more accurate and precise now that the Golden Gate Cetacean Researchers have acquired a permit to visit the porpoises by boat.
Bottlenoses normally live in Southern California, but sometimes migrate up into in the San Francisco Bay while the waters are warm. There are more porpoises in these waters than dolphins; about 9,000 porpoises live in the areas between San Mateo County and Mendocino County whereas only 400 dolphins inhabit the entirety of California’s waters.
However, dolphins are known to make more of a presence with their tricks. They are typically larger than porpoises with longer snouts and curvier dorsal fins.
In contrast, porpoises have more triangular dorsal fins.
Keep your eyes out for marine mammals!
Porpoise Project Leader of Golden Gate Cetacean Research Contact Info:
Photo Credit: Golden Gate Cetacean Research