From my buddy, Kim - a marine biologist, phenominal outdoorsman, Marin Native and general good guy:
this happens every year, from about Nov to Jan...the fish are Herring,
who lay their eggs on the Sausalito waterfront rip rap rocks (and other
locations in the bay), which in turn attracts amazing amount of wildlife
(birds, fish, rodents) and the
seasonal commercial and private Herring fisherman...it's quite a sight
to see...it's also a good time to fish for Sturgeon, as these pre
historic fish come close to shore to suck the eggs off the rocks."