The float was built specifically for the seals and is the only place on the Bay where they can be seen from a public trail
Late autumn and early winter is a great time to view harbor seals from the Bay Trail along Enterprise Park at Alameda Point.
It’s the only place on the San Francisco Bay where harbor seals can easily be observed from a public trail. The floating dock offers a visual connection with the timid and seldom-seen marine mammals, which are often mistaken for the gregarious attention-loving sea lions at San Francisco’s Pier 39.
Since Alameda’s harbor seal float is unaffected by tides, seals may spend half the day in the sun warming up because their fur coat cannot retain heat underwater indefinitely. Harbor seals have a unique ability to forage for food at night due to their sensitive whiskers that allow them to detect fish movement in the dark and maintain awareness of where the rest of their seal group is located.
In early December, the number of seals on the float typically begins to rise dramatically, from 40 or 50 up to more than 80, according to data collected by the volunteer group Alameda Point Harbor Seal Monitors. They’re drawn there by the combination of cooler temperatures and the herring that come to spawn in the area.
Ideal water temperature for herring spawning is between 50 and 53.6 degrees Fahrenheit. The water temperature at Alameda Point dropped below 54 degrees on the afternoon of December 16, 2017, and continued dropping another 2.3 degrees, according to data recorded by the National Oceanic and Atmospheric Administration’s Alameda Point scientific data station located a few hundred yards from the seal float. This brought on the herring run and, not surprisingly, the voracious seals.
The float is the only place in the East Bay between Yerba Buena Island and Newark where harbor seals can rest throughout the tide cycle, and it’s permanently adapted to sea level rise. It is also the only known floating structure in the world built specifically for harbor seals.
The access road on the west side of Encinal High School at 150 Central Avenue leads to the Encinal Boat Ramp, a parking lot, and the Bay Trail. It’s an easy walk or ride down the trail to an observation point next to the soccer field. For the best viewing, bring binoculars and come early in the day when the sun is above providing better lighting on the seals.
The float was built and deployed in 2016 when the Water Emergency Transportation Authority (WETA), also known as San Francisco Bay Ferry, was building its maintenance facility at Alameda Point. In order to build the facility, WETA had to destroy the Navy’s wooden dock that was being used by the seals. WETA built the float in response to lobbying by wildlife advocates as a concession for destroying the dock.
For those who have been following the harbor seals on the Alameda Point Harbor Seal Monitors’ Facebook page, there’s disappointing news. The page was recently hacked and corrupted, and Facebook took it down. Unfortunately it will not be possible to reactivate the site or retrieve its contents. Fortunately, however, there is another option for following the harbor seals’ status updates, photos, and videos, or to comment or ask questions on the Alameda Point Parks and Nature Facebook page.
Everyone who loves wildlife is encouraged to visit the observation point on the Bay Trail.
Contributing writer Richard Bangert posts stories and photos about environmental issues on his blog Alameda Point Environmental Report. His writing is collected at AlamedaPost.com/Richard-Bangert.
