Beyond the Shoreline – Harbor Seal Island off Encinal Beach


One of the best places in the San Francisco Bay to see harbor seals is in Alameda at a floating platform built just for them near Encinal Beach! Unlike their loud cousins the sea lions which visit Pier 39 in San Francisco, harbor seals are quiet, lack ear flaps, and can’t put their back flippers underneath their bodies. They are adept swimmers, ut out of the water they move like giant inchworm sausages.

Harbor seals need to come ashore to thermoregulate. “Hauling out” helps them warm up between swims in the cold water. They chase and eat fish like anchovies, as well as midshipman and other bottom dwellers. Large numbers of seals are attracted to schools of spawning herring during the winter. At the haul-out platform in Alameda, up to 80 seals have been seen squeezed-together in one day! In the spring, mother seals can be seen nursing their baby pups.

When the Water Emergency Transportation Authority (WETA) was planning to move their maintenance facilities to Alameda, they planned to destroy an old dilapidated dock where a few seals hung out. After public outcry from local citizen wildlife advocates, WETA financed the building of a floating platform for the seals to haul-out on. The platform is 20 by 25 feet, with one side sloped to allow seals easy access from the water, this is the only known floating platform in the world built specifically for seals. The platform is constructed of reinforced concrete with a Styrofoam core. Designed by marine mammal expert Dr. Jim Harvey, the director of San José State University’s Moss Landing Marine Laboratories, it is always available to the seals and is not subject to tidal fluctuations or sea level rise.

Harbor seals are protected under the Marine Mammal Protection Act, and their disturbance is a big concern being so close to an urban area. Boaters and paddlers are encouraged to watch from a distance. If the seals raise their heads, that signals that they feel threatened. With binoculars they can be easily seen from shore along the Bay Trail.

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To volunteer and report observations and numbers of seals contact:

Dave Mason, Public Information Supervisor