Schooling 101

As kids of all ages head back to classrooms across San Diego, and shorter days remind us that fall is around the corner,  Birch Aquarium looks closer at schooling fish in honor of one of the most exciting natural events of the summer.

 On July 8, 2014, a massive school of northern anchovies swam along the coast of La Jolla on their migration north. Scripps scientists say it is the largest school seen in more than 30 years. A school of fish is simply a group of fish of any size, ten or several thousand, swimming parallel in the same direction. It’s synchronized swimming, fish-style.

northern anchovy aggregation in La Jolla. July 8, 2014

Photo credit: Scripps Institution of Oceanography, UC San Diego

In the back-to-school spirit, let’s explore the schooling behavior of fish through core elementary “school” subjects.

Math: Is there really safety in numbers? Swimming as part of a group may reduce the likelihood of an individual fish being attacked by a predator. More fish = more targets. Predators have a more difficult time zeroing in on individual group members, making it statistically less likely that a particular fish will be picked off. A flurry of swirling baitfish may even disrupt the ability of predatory fish to sense their prey using their lateral line.

However, swimming in a large, conspicuous group can also skew the numbers game in the predator’s favor…

Physical Education: Sea lions, sharks, and sea birds rise to the challenge of feeding on open ocean fish using speed and agility. Interestingly, biologists recently discovered that billfishes, like sailfish and marlin, can insert their long, slender bills into schools of fish without scaring them. Talk about stealth! The billfish then tap targeted prey with their bill or slash through schools with powerful side-to-side thrusts (1).

Social Studies: If this has you worried, little fish, practice your cross-cultural skills. Some schooling fish swim alongside larger predators, like tuna or sharks, who serve as bodyguards. Other fishes form multi-species groups for better foraging. Zebraperch and opaleye in Birch Aquarium’s Kelp Forest often do this!

Oceanic whitetip photographed at the Elphinstone reef, Red Sea, Egypt, accompanied by pilot fish

Oceanic whitetip photographed at the Elphinstone reef, Red Sea, Egypt, accompanied by pilot fish. Photo licensed under Creative Commons Attribution-Share Alike 2.5 via Wikimedia Commons –

Recess: Do fish learn to school or is it instinct? This is not a well-investigated area of research, but some species have been observed to gradually attempt schooling behavior. Just as recess is time for socializing, young fish will practice swimming alongside each another in pairs, joining larger and larger groups as they develop ability.

After-school enrichment: If you enjoy the performing arts, check out the acrobatics of shrimpfish (Aeoliscus strigatus). These fish swim in a headstand position, with their tails up and heads down. The shrimpfish’s schooling “choreography” resembles blades of seagrass swaying back-and-forth in the water, helping them blend in with their seaweed home.

Birch Aquarium’s former executive director Dr. Nigella Hillgarth took a video of this behavior:

Want to spot more schools of fish at Birch Aquarium? Keep an eye out for blue-green chromis, shiner surfperch, and señoritas. Be sure to also check out our photography exhibit, Mexican Seas/Mares Mexicanos, for sardines, trevally, and more.


Kate Jirik

(1) Domenici P. et al. 2014. How sailfish use their bills to capture schooling prey. Proc. R. Soc. B 281: 20140444.


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Scripps Institution of Oceanography UC San Diego