Excerpt:

Alameda Point’s harbor seal population fluctuates between single digits and 50 during most of the year on the specially-built harbor seal float. But when the Pacific herring arrive in the winter to lay their eggs, many more seals arrive to feast on the herring, causing a sudden spike. Last winter, a spike in seal numbers to a record 70 came on January 5, 2017, in the midst of the herring run. This winter, the herring arrived sooner, in December, and so did more harbor seals, causing a spike to a new record of 73 on Christmas Eve and Christmas Day.