Mike Bear had just slipped underwater, offshore near San Diego, and was floating among the long fronds of a kelp forest when a long shadow passed between him and his diving partner. Gliding by, nearly within arm’s reach, was the sleek bulk of a sevengill shark, which Bear estimated at about nine feet long.
“To say we were startled would be an understatement,” Bear, a lifelong diver, says. The encounter, not uncommon among sevengill sharks, which inhabit the Pacific coast of the United States, left a lasting impression on Bear. It spurred him to co-found Ocean Sanctuaries, a non-profit organization that helps divers and ocean enthusiasts track sharks and other sea creatures.
The organization operates multiple programs that allow and encourage divers to submit images of sharks seen on dives to a database scientists use to learn about shark habitats and behavior. Understanding sharks helps us protect and conserve the species and their ocean ecosystems. Scientists depend on real-life observations of sharks to learn about their lives, but the oceans are vast, and it’s not possible to monitor much of them. But the millions of amateur divers exploring waters around the world function as an extended network of observers, vastly expanding the amount of data that can be collected.
Ocean Sanctuaries’ project to gather observations of sevengill sharks has been running since 2013, gathering thousands of sightings that let scientists build critical knowledge about where the sharks live and how they act. Artificial intelligence allows individual sharks to be identified based on the patterns of freckles on their skin, letting scientists track them over time. Different projects from Ocean Sanctuaries, and from other groups like eShark, are doing the same for other shark species around the world.
As sharks face increasing threats around the world, these observations are becoming more valuable than ever before.
Image credit: C Ward-Paige
Sevengill sharks, and hundreds of other species of shark, continue to be threatened by human activities, and are hunted for their fins to make shark fin soup. Around 25 percent of shark and ray species, together known as elasmobranches, are considered endangered, according to the World Wildlife Fund. Every year, a staggering 100 million sharks are killed by humans, a 2013 study estimates, a massive toll that could lead many species to extinction.
Shark numbers are important for other species as well. In many places in the ocean, they sit atop an intricate food web, acting as apex predators that keep ecosystems humming.
“If we allow sharks to go extinct, then when the top predator is removed from the ecosystem, it’s going to have a cascading effect all the way down the food chain,” Bear says.
Scientists and conservationists are scrambling to protect sharks and rays through initiatives that reduce bycatch, protect swaths of ocean and educate the public about the value of sharks to ecosystems and to humanity. These efforts are beginning to yield victories, but scientists are still constrained by a dearth of knowledge about sharks and rays, who range throughout the largely unexplored oceans.
Image credit: Simon Pierce
Citizen science projects are beginning to fill that hole in our knowledge. Wildbook for Sharks, a project supported by conservation organization Wild Me, lists over 100,000 shark sightings by around 10,000 citizen scientists. A recent study in the Journal of Fish Biology notes that citizen science efforts have expanded our understanding of whale sharks at locations including Southern Leyte in the Philippines, the Arabian Gulf and Ningaloo Reef in Australia. That included evidence of one individual, named P-1159, traveling between the Philippines and Malaysia, a journey of around 500 miles that hadn’t been documented before.
Other studies using citizen science data have begun to piece together the nuances of behavior of various species of shark. A 2023 study drawing from citizen science observations in Los Cabos, Mexico, for example, found that shortfin mako sharks were more likely than other shark species to be seen when waters were cooler, and that hammerhead sharks were more prevalent when the moon was full. A similar study from 2022 on great white sharks near South Africa found their numbers peaked in the winter, and sightings correlated with air temperatures and seal activity.
Not all shark citizen science happens in the ocean, either. Since 2014, the Great Eggcase Hunt has been gathering sightings of “mermaid’s purses,” or the empty egg cases of sharks and rays that wash up on beaches. The project, which began in the United Kingdom, but has since become international, asks volunteers to submit observations of egg cases, which scientists use to monitor population numbers. One recent study using data from the project was even able to estimate how many egg cases get eaten by predators, based on tooth marks. Around 15 percent of the shark and ray egg cases bore evidence of predation, the researchers found, with little difference between elasmobranch species. The size and shape of the tooth marks pointed to gastropods and octopuses as the likely culprits.
Image credit: Great Eggcase Hunt
Citizen science projects could also address what Bear says is one major problem still facing sharks: their public image.
“There’s a big fear factor when it comes to sharks,” Bear says. That fear even has a name, galeophobia, from the Latin “galeos” for shark and “phobos” for fear. It’s a barrier that may be hurting sharks, awe-inspiring though they may be. “They’re not warm and fuzzy, they’re not cute and cuddly like pandas or dolphins,” he says.
By helping more people to understand the immense value sharks add to ecosystems, and perhaps even be inspired to find some themselves, we may be able to turn the tide of looming shark extinctions around the world. No matter if you’re getting in the water yourself, or just observing them from afar, your observations, and your attention can make a difference for sharks everywhere.