The San Francisco Bay supports a rich diversity of fish, with estimates suggesting over 130 species use the estuary for all or part of their life cycles, including important salmon, sturgeon, smelt, and surfperch, plus many introduced species, making it a vital habitat for both native and non-native fish populations. There are three wildly different fish that highlight the interplay of fish with native oysters and eelgrass in the Bay.
Pacific Herring
Clupea pallasii
Pacific herring are a vital species in San Francisco Bay, forming the foundation of the bay’s winter marine ecology and fueling both natural food chains and commercial fisheries. Each year, from December through March, Pacific herring typically return from the open Pacific to spawn in the bay’s shallow, protected waters. During these winter months, they congregate in dense schools, moving into intertidal and shallow subtidal zones as they prepare to spawn. At three to four years of age, females lay as many as 20,000 sticky eggs, usually attaching them to submerged vegetation like eelgrass or kelp, onto rocks and cobbled beaches, or even artificial structures such as pier pilings and riprap.
Eelgrass with roe
Males simultaneously release clouds of milt, fertilizing the eggs in the water. This collective process lasts between two to four days. The telltale milky nearshore water is a sight anticipated by many who live along the Bay’s shores—especially around Richardson Bay and across on the eastern shores at Richmond—an assurance that the herring life cycles are in sync. Herring Roe on kelp is a traditional delicacy favored by Tribes and First Nations up the coast to the north, but is only allowed as a commercial fishery in California in San Francisco Bay. Blades of giant kelp are suspended off of marinas in Sausalito to catch herring roe.
Pacific herring
Young herring spend their first summer of life in the realm of the Olympia oyster. The shallow inlets and channels along the nearshore areas of the Bay, with eelgrass nearby for protection and plenty of nutritious mollusk larvae floating around, including the oyster’s summertime spawn, is fertile territory for young fish to mature. They will eventually move into deeper water and eat larger crustaceans and small fish, becoming prime targets for larger predators themselves. The vast ocean food web starts at the margins when oysters release larvae, eaten by very young herring that in turn get scooped up by the least tern skimming the water’s surface, or gobbled by sturgeon snarfing through the eelgrass or stabbed by the great blue heron, stalking the muddy shore on its long stilty legs.
Yet the great runs of herring into the Bay in the 1970s and 80s, remembered by older fishermen as the small wisps of silver literally filling the water’s surface and milky spawn reaching for miles of coastline, are a thing of the past. Whether because of dwindling food supply, reduced habitat, warming ocean temperatures, or all of the above, the herring biomass measured by CDFW (California Fish and Wildlife) has dwindled since 2014 to mere fractions of the historical average.
White Sturgeon
Sinosturio transmontanus
While Olympia oysters are small but strong indicators of San Francisco Bay health, sturgeon are big fish indicators of the Bay’s health. And like Ostrea lurida, Sinosturio has come through profound changes in the conditions of our earth, since the time of the dinosaurs, to be an ancestor in our current San Francisco Bay. Oyster and sturgeon might each be considered respected totems of the muddy bottom of the Bay, the sturgeon rooting around aerating the mud so that worms, clams, and other mud dwellers have the oxygen they need.
Sturgeon have soft flesh, no scales and a mouth on the bottom of their head to sift through mud.
The 20-foot, one-ton resident white sturgeon of San Francisco Bay past are all but forgotten, now only found around 5-6 feet long. White sturgeon are semi-anadromous, living in the Bay but migrating up into freshwater to spawn. Green sturgeon, on the other hand, are like salmon, spawning higher up in the rivers, growing to maturity in the fertile waters around San Francisco Bay, then migrating out the Golden Gate and up the Pacific Coast to feed off the coasts of Washington and British Columbia. They return periodically to spawn in their home waters up the Sacramento River. These ancient fish are part of the San Francisco Bay, but few people know they are there.
Sturgeon were trapped illegally in Jack London’s day (1890s) by fishermen using a line of hooks unavoidable to fish that travel along the bottom, foraging by feel and smell in the murky waters for clams, amphipods, shrimp, crab, snails, and other fish.
“Such a fish is the sturgeon, which goes rooting along like a pig, and indeed is often called “pig-fish.” Pricked by the first hook it touches, the sturgeon gives a startled leap and comes into contact with half a dozen more hooks. Then it threshes wildly until it receives hook after hook into its soft flesh; and the hooks, straining from many different angles, hold the luckless fish until it is drowned.”
Sturgeon
Sturgeon have also been a startling indicator of the deadly effects of harmful algal blooms or HABs. HABs occur when too many nutrients, often from agricultural run-off, cause an explosion of phytoplankton. Toxins can be directly associated with the overpopulation of algae, but it is the mass of bacteria that eat the mats of algae that suck up all the oxygen in surrounding waters, leaving none for other fish and animals to breathe. In the summer of 2022, an enormous bloom of a particular phytoplankton, Heterosigma akashiwo, reduced oxygen levels throughout the San Francisco Bay, causing mass fish die-offs and particularly impacting sturgeon. Almost 700 sturgeon carcasses, both green and white, were documented by citizen science surveys and iNaturalist reports (and analyzed by sturgeon researchers) from the southern tip of the South Bay, through the Central Bay, and all over San Pablo Bay in the north. Before the reordering of the bay and delta by agriculture and people, when native oysters covered the bottom of the bay, and along the margins, their millions of gills sieved water for nutrient algae, helping maintain the balance between phototrophs and all the creatures needing to breathe oxygen in the water.
Sturgeon can grow to be 80 years old, spawning only every few years, so a mass die-off is tragic for this long-lived, prehistoric, scaleless fish that can emerge from the dim bottom of the bay in athletic jumps at the surface. Acknowledging their presence in our local waters, alongside the Olympia oyster, can be a wake-up call to restore water flows, and manage pollution levels, around the Bay so their cycles of life can again flourish.
Bay Goby
Lepidogobius lepidus
The Bay Goby (Lepidogobius lepidus), is a tiny fish, no bigger than a pinky finger, and a native to muddy creeks and tidal shorelines of San Francisco Bay, easily adapting to brackish water with changing salinities. The Bay goby burrows into the mud or finds nooks and crannies to hide in; a cluster of Olympia oysters or an eelgrass patch offer the perfect refuge from predators. Bay gobies have a relatively short lifespan—rarely living longer than a year—but their populations can recover rapidly from disturbances.
Cameleon Goby
Breeding occurs during warmer months, with males constructing burrows where courtship rituals take place; females lay eggs in the burrows that the males then guard until hatched. The young gobies hatch into planktonic larvae, a food source for many others, before settling back into benthic habitats as they mature. The species’ resilience make bay gobies an important part of the San Francisco Bay’s ecological web, an interesting, tiny curiosity for us humans—they have no commercial value whatsoever.
Another goby, the chameleon goby, is not native to San Francisco Bay but has become an established part of the complex of small fishes that eat and are eaten within the trophic food webs of the Bay. As fry they are eaten by crabs, birds, and larger fish. Male chameleon gobies also make nests where a female will lay her eggs, usually in an old oyster or clam shell or other crevices. The reuse of materials is an oyster’s gift to the community around it, either as substrate for its own offspring to build its life upon, or as a nest for the tiny goby eggs—a home within which to be fertilized and watched over—a tiny world of productivity and life at the scale of an Olympia oyster shell.
