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.
On December 23, there were so many seals looking for a place to get out of the water and warm up at Alameda Point that 53 had to climb onto the rock wall known as Breakwater Island, another record.
The seasonably colder water temperatures lead to a spike in the number of harbor seals making use of the float. Winter herring spawning in the vicinity also attracts greater numbers of seals. The central part of San Francisco Bay has the highest density of fish species throughout the year, according to the CA Department of Fish and Wildlife, making the Alameda Point float uniquely convenient for the seals.
The specially-built harbor seal float was deployed at Alameda Point in June 2016, paid for by the Water Emergency Transportation Authority which built and operates the nearby ferry maintenance facility. It is the only known floating platform in the world that was built specifically for use by harbor seals, whose shoreline habitat for resting and giving birth will face growing impacts as sea level rises.
The harbor seals can easily be viewed from the Bay Trail, which runs between the Encinal Boat Ramp and the ferry facility. After 1 PM is a good bet for seeing the most seals in December and January.
More info and updates on the seals can be found on the Alameda Point Harbor Seal Monitors Facebook page.