Pacific Herring, or Clupea pallasii, are back in the Bay! These distinct, silvery fish travel in schools and feed on plankton. The first wave of herring has returned to the Bay estuary for their annual spawning, which typically starts in November. Tomales Bay and the San Francisco Bay are in fact the only spawning places south of British Columbia for this species of herring. The schools swim in through the Golden Gate beginning in November and gather in the deeper channels to spawn. The process entails female herring laying unfertilized eggs, also called roe, onto rocks, seaweed, or pier pilings, and males subsequently fertilize the eggs. Roe may be familiar to some in the form of bright orange sushi toppings.
Pacific Herring live most of their lives in the open ocean, living up to ten years, and ranging from 4 to 8 inches in size. The schools of herring settle in estuaries during spawning season because of the abundance of plankton and nutrients. Estuaries also provide great habitat for them to lay their eggs. Herring have been known to prefer Richardson Bay, which is located in Marin County between the cities of Tiburon and Sausalito. Richardson Bay offers abundant eelgrass and other sub tidal vegetation, as well as the right salinity and currents. Herring usually rush into the Bay in several waves until about mid-March.
This year, Pacific Herring have come back to the Bay once again, which is great news for the dozens of bird species, sea lions, and porpoises who depend on herring as vital prey. The herring runs have attracted an estimated number of 23,000 birds visit last year to Richardson Bay. In the late 1990s, herring populations were declining and dropped to historically low numbers in 2009. Scientists fault warmer water and the lack of food sources in the ocean for the decline in numbers. Seeing the thriving herring runs this winter brings us hope and joy and is a good sign for the San Francisco Bay. The return of these shiny, impressive fish may signify improving health of Bay waters.
To read more and watch an extraordinary video of hundreds of gulls respond to herring, take a look at this article. And when you have the chance, get out to the shorelines, such as Miller/Knox Regional Shoreline, and see the herring runs for yourself!