harbor seals – Alameda Point Environmental Report

Harbor seals make use of commercial dock in Seaplane Lagoon

Over the years, harbor seal observers on the former Alameda Point Harbor Seal Monitors Facebook page often asked, “Do we need another harbor seal float?” It appears the seals have provided their own answer.

December is when the numbers of harbor seals start increasing at Alameda Point in anticipation of the winter herring spawning in the vicinity. The influx of seals leads to overcrowding on the specially built float near the ferry maintenance facility and Bay Trail. It has been happening since the harbor seal float was deployed in the summer of 2016. Again this December, the float has been fully occupied with as many as 75 seals (verified by numbering a printed photo) during part of the day and not an inch to spare.

Harbor seals arriving at Alameda Point this December found an alternative spot to the overcrowded float when they ventured into the nearby Seaplane Lagoon. Their additional haul-out location is on a plastic commercial dock owned by Saildrone, the maker of autonomous battery-powered boats capable of gathering marine scientific data around the world. Saildrone vessels, manufactured in a hangar on West Tower Avenue, can often be seen moored in their leased space in the Seaplane Lagoon.

Best time to view the harbor seals at Alameda Point

Late autumn and early winter is a great time to view harbor seals from the Bay Trail along Enterprise Park at Alameda Point.

It is the only place on San Francisco Bay where harbor seals can be easily observed from a public trail. The floating dock offers a visual connection with a timid and seldom-seen marine mammal, which is often mistaken for the gregarious attention-loving sea lions at San Francisco’s Pier 39.

Harbor seal molting and mating behavior up close

Shedding and replacing fur coats

Every summer, and even into the fall, harbor seals go through a biological process known as molting, in which they shed their fur and grow a new layer to keep their fur healthy. You can tell when they are molting by the patchy appearance of their fur.

Harbor seal update: Float research, whiskers for survival, and boating etiquette

Alameda Point harbor seal float inspires research at New York Aquarium

The harbor seal float at Alameda Point has been wildly successful. It started out as an experiment. Now it’s a model being studied at the New York Aquarium.

In July 2022, the Wildlife Conservation Society’s New York Aquarium installed a float in an exhibit modeled after the float at Alameda Point. The research project was initiated by aquarium keeper Payden Sra as part of her work toward a graduate degree. Studying haul-out behavior of harbor seals in a controlled setting “can better advise conservation actions for the growing wild seal populations managed by local officials on the East Coast,” Sra wrote in the description of her study. “While once a rare sight, it is increasingly common to see seals in New York.”

Alameda Point harbor seals attract educational groups

About 240 students from Eldorado Middle School in Concord visited Alameda Point to make observations of the harbor seals on March 22. The school participates in an educational program sponsored by the Marine Mammal Center in Sausalito called Ocean Ambassadors.

The students arrived in two groups. While the first group was at the trailside viewing site, a second group was on a ferry ride around San Francisco Bay to view marine wildlife. The second group arrived in the afternoon, while the first group went on the ferry excursion.

Alameda Point was chosen for viewing harbor seals because it is the only place on the Bay that is easily accessible for viewing seals.

Harbor seal pup grows up at Alameda Point

A harbor seal pup is being raised by its mom at Alameda Point. It is the fourth year in a row that a pup has been observed utilizing the harbor seal float. It is unknown where any of the pups were born.

Here is a gallery of photos from April showing the pup nursing, resting on the float, and riding on its mother’s back in the harbor. The pup can be identified when on the float as the one with the light gray coat. Continue reading “Harbor seal pup grows up at Alameda Point”

Harbor seals max out their float in December

On December 23, the number of harbor seals on the float at Alameda Point reached 80, a new record for a single day. The number of seals on the float exceeded 70 on 10 days during December, a new record for the month.

Seals were packed so tightly that some were barely hanging onto the edge. The cramped conditions when the float reaches 70 seals in December and January can lead to bouts of slapping and shoving, as harbor seals prefer to have some space when resting. Continue reading “Harbor seals max out their float in December”