What fish are in the bay
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Yesterday afternoon I went for a jog along the Bay Trail and saw a bunch of little fish flipping around near the surface right at the edge of the beach. What were they? Were they being chased by something?–A.J., Alameda
Fishes flip and jump for a variety of reasons. Sturgeon, for example, are thought to do it for communication. The massive, Jurassic-period descendants migrate upstream to spawn during the muddy water flows of winter and spring when it’s hard to see even inches into the water. Anyone who’s ever witnessed or experienced a belly-flop at the pool (ouch!) knows that the sound of a six-foot creature slapping the water sure gets attention! What an amazing thrill to hear the slap of a massive white sturgeon (Acipenser transmontanus) after it leaps from the water under a moonlit sky in the spring. Sturgeon happen to jump most frequently at the height of their breeding season, when presumably they want to find one another the most (queue the Barry White tunes).
Rainwater killifish collected in Lake Merritt in October 2019. (Photo by Katie Noonan, iNaturalist CC)
The first question I have to ask when someone tells me they saw fish jumping is “how many, and how big?” On the opposite end of the size spectrum from the sturgeon are the mosquito larvae-munching rainwater killifish (Lucania parva), a guppy-sized eastern U.S. species that was first seen in California at Berkeley’s Aquatic Lagoon (that long tidal pond next to I-80) in 1958. With the ability to handle freshwater and a range of salinity as high as three times that of the ocean, they’re just about everywhere today. Whether they got here in ballast water, as eggs hitching a ride with a shipment of oysters, or mixed with mosquito-controlling Gambusia from the other side of the continental divide is beside the point – these omnipresent pigeons of the fish world earn their common name from the little ripples they make as they scurry and feed at the surface of a glassy-surfaced pond. It’s not so much a “flip” as a flitting about, and en masse you’d be fooled into thinking the little rings at the water’s surface were caused by raindrops. Most typically this happens at dusk when the water is still warm from the sun and the mosquitoes are getting active. But you were at the beach, and there were probably waves, so I’m going to abandon that hypothesis.
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What you saw along the beach was likely a shoal of California anchovy, AKA northern anchovy (Engraulis mordax), which have been described as the most abundant fish in the Bay. Note that I said “shoal” and not “school.” There’s a slight difference. A shoal is what we call a social grouping of fish. Schooling is the “synchronized swimming” behavior a shoal might do when they tighten up en masse for protection from predators. Schooling is a kind of shoaling, not the other way around.
Whether feeding or breeding (which some anchovy shoals do year-round), as plankton feeders, anchovies not only school for protection, but to feed more efficiently. Much like a diving flock of cormorants will hunt in a row, anchovies will work together as a school to gobble up zooplankton and tiny critters in their path. The ones you saw at the beach were likely eating, spawning, or both.
A humpback lunge feeds under the Golden Gate Bridge in November 2018. You can see anchovies leaping from the whale’s mouth. (Photo by Bill Keener, Golden Gate Cetacean Research)
If your anchovies were being chased and cornered by striped bass, halibut, or perhaps a harbor seal, you would have seen much bigger splashes. In fishing lingo they’re called “boils.” And speaking of big splashes, remember that humpback whale that was jumping in Alameda in summer 2019? It was corralling shoals of northern anchovies into an enclosed lagoon, frightening them into schools, and devouring them to bulk-up. It’s quite effective to corner prey near the shore like that!
The moral of the story? When you see things jumping by the shore, they’re probably eating, or making sweet, fishy love. Isn’t nature amazing?
Ask the Naturalist is a reader-funded bimonthly column with the California Center for Natural History that answers your questions about the natural world of the San Francisco Bay Area. Have a question for the naturalist? Fill out our question form or email us at atn at baynature.org!
About the Author
James Frank is a career naturalist and science educator who grew up romping through the woods, salt marshes, and bays of the East Coast. He came to California ten years ago by way of a nature center he managed on the Chesapeake Bay. Currently he’s a naturalist in the East Bay. When he’s not working, he’s probably fishing or taking his kids outdoors.
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Striped bass, also know as rockfish.
Will Parson, Chesapeake Bay Program
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Each spring in the Chesapeake Bay, something miraculous happens: fish return home. Thousands of river herring, shad, striped bass, and others find their way from the ocean back to the Bay’s tributary rivers to spawn, a spectacle that unveils this estuary’s awesome capacity for life. But while fish and shellfish continue to generate billions of dollars each year in Bay states, decades of overfishing, pollution, habitat loss, and now climate change, have put many species in trouble—including striped bass, or rockfish. Learn how coastwide fishery managers are shaping a new management plan for rockfish that will set the course for their management for the next decade or more, and how you can help. Then, check out the successful completion of oyster reef restoration projects in the Little Choptank and Elizabeth River (providing key habitat for fish), and find out why changing the inspection policy for invasive blue catfish could help both commercial fishermen and native fish species. Finally, learn about the unique adaptations of Chesapeake Bay fish, the kickoff of trout season in Pennsylvania, and the latest news around the watershed.
The Future of Rockfish
Amid worrying signs that striped bass, or rockfish, are in trouble, the coastwide management plan for this iconic Bay species is being rewritten. Learn about the ASMFC—the fishery management body at the helm—and how managers can chart a course for success. You can help: Raise your voice for rockfish, and follow safe fish handling practices when angling.
CBF’s oyster restoration vessel, the “Patricia Campbell,” motors across the Bay with 4 million oysters on its deck to be planted in the Little Choptank River on a sanctuary reef in the spring of 2016.
Oyster Rivers Restored
The large-scale restoration of oyster reef habitat in the Bay’s tributary rivers is key to help oysters, fish, and other wildlife thrive. In the last few years, CBF worked with partners to complete one of the world’s largest oyster restoration projects in the Little Choptank River, and another in the “lost branch” of Virginia’s Elizabeth River.
VIDEO: Cool Fish Adaptations
What can you learn about a fish’s food source, habitat, and lifestyle just from looking at it? Join CBF Educator Tiffany Granberg to explore the unique adaptations of Chesapeake Bay fish that allow them to thrive in the Bay’s varied environments. Then, test your knowledge with our Fish Adaptations Investigation.
Pennsylvania Fish and Boat Commission Executive Director Tim Schaeffer releases a bucket of trout during the 2020 fishing season.
BJ Small/CBF Staff
Trout Time
Last year was unlike any other for most things in life. The trout fishing season in Pennsylvania was no different. Managers explain how they brought anglers and fish together despite the odds, including a clandestine opening day and social distancing guidelines, and what’s coming up this year.
Blue Catfish: The Next Big Catch?
Blue catfish are an invasive species found in tributaries throughout the Bay watershed. Scientists worry their spread could harm native species such as menhaden, striped bass, shad, and blue crabs. Changing an expensive and cumbersome inspection process could help the problem and boost a commercial fishery, too.
Will Parson/Chesapeake Bay Program
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From climate bills in Maryland to environmental education standards in Pennsylvania to balloon bans and clean water investments in Virginia, find out what Bay happenings made headlines this month in our latest Around the Bay in 60 Seconds video.
