In Order to Unravel the Many Mysteries of Squids, Scientists Dive Into Their Mating Frenzies
Marine biologists hope to find out more about a creature that is vital to a healthy ecosystem and the state’s fishery
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Lit by the fading sunset and the emerging moon, the two scientists zip up their wetsuits and head out to the beach of La Jolla Shores in Southern California. Soon after, marine biologist Theodora Mautz and her dive buddy, physical oceanographer Gabriel Gekas, kick out into the inky waters of the cold Pacific Ocean. While floating above the nearshore submarine canyon, Mautz and Gekas look at each other, switch on their dive lights and give each other a thumbs down, a diver’s signal to descend. They submerge, slipping into the aftermath of a squid orgy.
As the researchers descend onto the seabed, their lights illuminate a field of white egg capsules. Each egg capsule is about six inches, or two-thirds the size of the squid that laid it. The eggs stretch as far as the divers can see. But three weeks after the run of squids that led to this cephalopod nursery, no live adults are to be seen.
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For weeks preceding Mautz and Gekas’ dive, scuba divers in La Jolla experienced an astonishing event called a “squid run.” When it is time for opalescent squids (Doryteuthis opalescens) to breed, they gather in the tens of thousands off of the California coast, spending mere days in a mating frenzy, an event local dive master Brandon Wiese calls “a blizzard of life.” When Mautz heard these reports, she knew she needed to move quickly. Her PhD research is predicated on her ability to make field observations of the run, an event that could only last those mere nights in a year, if at all. Squid runs are typical during La Niña years, in which the predominant climatic pattern over the equatorial Pacific is cooler than average. This year’s La Niña comes directly after an El Niño year, which produces warmer temperatures in the equatorial Pacific, possibly offering clues as to how squid runs will fare after dramatic changes.
Mautz and other scientists are looking to learn more about squid behavior, development and population changes. The animals are an important middle rung of the ocean ecosystem, as they serve as both a significant predator and a prey item for hundreds of species. The animals are also a highly fished species that supports the livelihoods of thousands of Californians every year. But squids are notoriously hard to study and understand, and this run offers scientists a rare opportunity to learn their secrets.
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Opalescent squids live on the continental shelf, where the crust lies 300 to 600 feet deep. The squids often come up to the surface at night to feed on small fish and invertebrates. While individuals will sometimes swim to the shallows, the squids gather en masse at observable depths during their mating event. In a phenomenon known by scientists as “big bang mating,” large synchronized spawning groups get together in the tens of thousands, lay enough eggs to replace the entirety of their population, then perish after only a few days.
This year’s observations documented something different than a normal big bang. Instead of an aggregation lasting just a few days, waves of squids converged in a staggered event that lasted three weeks. Over that time, the animals slowly built up the egg field that Mautz and Gekas dove upon. Scientists call such a long occurrence a “mega-aggregation.”
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The gathering creates an in-ocean laboratory that allows scientists to understand the conditions that set off squid runs and the behavior that happens within them. Mautz, a PhD student at the Scripps Institution of Oceanography, is working to understand the inner workings of squid romance. She wants to know more, essentially, about how male and female squids flirt—and the role visual signals play in that.
During the run, Mautz sought clues on how squids send mating messages. Squids are colorblind yet use color in almost every part of their mating behavior. Why? According to Mautz, squids interpret visual signals through contrast. As squids brighten and darken their chromatophores, special color-changing cells, the contrast against the white of their bodies offers messages to potential mates. Mautz says that these special cells, along with cells that help squids control polarized light and their white coloration, can help to give female squids a certain level of control in the mating process; female opalescent squids “selectively turn on these cells” to ward off mating advances. This behavior, hypothesized to help mimic male anatomy, could encourage males to avoid seducing uninterested females.
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Scientists are beginning to learn even more about the squids as their range expands into new areas. Mike Navarro, an oceanographer at the University of Alaska Southeast, studied opalescent squids during his PhD at the Scripps Institution of Oceanography. He never expected to see his Southern California study species when he began working in Alaska. But after a strong marine heat wave in 2017, reports of squids laying eggs on crab pots off Kodiak Island started to trickle in, and Navarro’s colleagues began joking that he is one of the only scientists whose study species followed them to a new location.
A team at Stanford’s Hopkins Marine Station determined the squids temporarily moved to Alaska as the animals followed water with more prey and oxygen, parameters that attract squids to begin breeding. Off Southern California, squids move off the continental shelf and closer to the beach for similar reasons, following favorable conditions.
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Caitlin Allen Akselrud, a fisheries and sustainability scientist at the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center, says that when she thinks about squid, she thinks about four things: “plates, baits, goods and livelihoods.” On plates, squid is a sustainable protein in dishes like calamari. Squid, a favorite food of many game fish, is also a high-quality bait. As a good, squid is shipped out to Asian countries en masse, whose markets revere it for its “nutty, sweet and delicate” taste, said Diane Pleschner-Steele, then the executive director of the California Wetfish Producers Association, in a 2016 interview with NPR. In terms of livelihoods, the squid industry supports not only fisherfolk and processors but also people in markets and hospitality who serve them, explains Allen Akselrud.
To keep the fishery healthy, scientists, fisherfolk and legislators have put together the Market Squid Fishery Management Plan. The plan, adopted in 2004, includes weekend fishery closures and regulations regarding the lights fishers use to attract the animals—as it aims to reduce the potential for overfishing and ensure the long-term conservation of the creatures. Currently, the plan is being reviewed, with parties voting on new amendments in June 2025. One change to the plan would require updated net parts that reduce contact with the ocean floor, where the egg beds are located.
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To determine the impact of these conservation goals, scientists need a way to understand the true size of the opalescent squid population. Estimating population numbers, even during runs, is challenging. Allen Akselrud is developing new machine-learning tools that use historical catch data, scientific survey data and environmental conditions to help scientists estimate runs. She notes that predicting population size and movement is like “forecasting the weather,” and she hopes her model will be helpful in the future.
During the recent run, while diving the egg field, Mautz finally did find a group of mating adults. The stragglers, she says, made her feel like a “cephalopod Jane Goodall.” The squids welcomed her into their secret world, she says, with the key to their mysteries drifting just before her eyes.
Editors' note, May 8, 2025: This story originally misstated when Mautz was in school and the behavior of certain squids, and has been updated. We regret the error.