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Baby sharks linger in the shallow water




a juvenile shark following an autonomous underwater robot

The Central California coast turns out to be a playground for baby sharks. Earlier this year we caught a glimpse of what could be the first images of a newborn great white shark. Now we’re learning more about where they like to live during their formative years. Young great white sharks select warm and shallow waters and congregate about half a mile offshore. These findings are described in a study published April 19 in the journal Frontiers in marine sciences and could have crucial conservation implications.

This water column is too cold

After they are born, baby great white sharks, also called pups, do not receive any care from their parents. This new study looked at one of these populations of juvenile sharks at Padaro Beach near Santa Barbara in Central California. Here, pups and juveniles gather in ‘nurseries’ and are not accompanied by adults in a kind of shark never never countryexcept these fish will eventually mature.

“This is one of the largest and most detailed studies of its kind. Because large numbers of juveniles share habitats close to shore around Padaro Beach, we could learn how environmental conditions influence their movements,” said study co-author from California State University. Marine biologist Christopher Lowe of Long Beach said in a statement. “You rarely see great white sharks exhibiting this type of brooding behavior in other locations.”

[Related: This could be the first newborn great white shark ever captured on camera.]

In 2020 and 2021 the team 22 young people tagged with sensor transmitters. Great white sharks can do that live between 40 and 70 years and the younger sharks in this study were all females and males between one and six years old. The sensor transmitters measure the local water pressure and temperature in real time. They also tracked the position of each shark by sending ‘pings’ to several receivers spread out about three kilometers along the coastline.

When the juveniles temporarily moved to offshore waters during the winter, tracking was stopped. The team collected more information about the temperature distribution using an autonomous underwater vehicle. With this data in hand, they used artificial intelligence generate a 3D model of the young people’s temperature and depth preferences.

Track results for multiple young people at the same time. This data was collected on October 16, 2023. CREDIT: Emily Spurgeon

The young people dived to the greatest depths around sunrise and sunset. This is probably when they were looking for rays, skates and schooling fish. They came closer to the surface – between zero and 4 meters deep – during the afternoon, when the sun was warmest. This shift to the warmer water could potentially increase their body temperature. They immediately changed their vertical position within the water column to remain between 60 degrees and 71 degrees Fahrenheit. Their sweet spot also turned out to be between 68 and 71 degrees.

“This may be optimal to maximize growth efficiency within the nursery,” study co-author and California State University, Long Beach research technician Emily Spurgeon said in a statement.

It stays with the shallow water

The temperature distribution in the water changes quite often, which means that the juveniles must be constantly moving to stay within the optimal range. They believe this is the reason young great white sharks spend more time in shallow water than adults. Furthermore, adult sharks were rarely observed in the nursery.

[Related: With new tags, researchers can track sharks into the inky depths of the ocean’s Twilight Zone.]

According to the teamthe results show that the temperature distribution over three dimensions had a strong influence on the way the young sharks were dispersed. They spread out at greater depths when seafloor temperatures were warmer, and moved closer together toward the water surface when deeper water was cooler.

young great white shark seen from a boat with its fin out of the water.  the coastline is also visible
Young great white shark seen from a boat. CREDIT: Emily Spurgeon

However, the team is still unsure what benefits the puppies and young people will get from meeting in nurseries at all. It could potentially help them avoid predators like some whales.

“Our results show that water temperature is a key factor attracting young people to the studied area,” says Spurgeon. “However, there are many locations along the California coast with similar environmental conditions, so temperature is not the whole story. Future experiments will look at individual relationships, for example to see if some individuals move side by side between farms.”

Great white sharks do considered vulnerable, with populations declining in some parts of the world. Knowing where baby and young sharks like to hang out could help pass better conservation laws to protect them as a species. It can also help protect the public from negative shark encounters.