Baby sharks prefer to be closer to the coast

April 19 () –

Marine scientists have shown for the first time that juvenile great white sharks select warm and shallow waters to group one kilometer from the coast.

These results, published in 'Frontiers in Marine Science'are important for the conservation of great white sharks (especially as ocean temperatures rise due to climate change) and to protect the public from negative encounters with sharks.

Great white shark pups do not receive any maternal care after birth. In the population studied off Padaro Beach, near Santa Barbara, in central California, cubs and juveniles gather in “daycare centers” without the company of adults.

“This is one of the largest and most detailed studies of its kind. Because around Padaro Beach, large numbers of juveniles share nearshore habitats, we could learn how environmental conditions influence their movements,” he comments. it's a statement lead author Dr. Christopher Lowe, professor at California State University.

In 2020 and 2021, Lowe and his team used darts to tag a total of 22 youths with sensor-transmitters. They were females and males aged between one and six years. Great white sharks can live between 40 and 70 years.

The sensor-transmitters measured local water pressure and temperature in real time and tracked the position of each juvenile by sending acoustic “pings” to a series of receivers, spread over approximately 5.5 square kilometers along the coast. These methods had been approved by the university's Animal Care and Use Committee and the California Department of Fish and Wildlife.

Monitoring stopped during the winter months, when juveniles temporarily departed for coastal waters. The researchers collected more data on the temperature distribution throughout the local water column with an autonomous underwater vehicle. They then used artificial intelligence to train a 3D model of the juveniles' temperature and depth preferences.

The results showed that juveniles dived to greater depths around dawn and dusk, when they were likely searching for rays, schooling fish, and other small bony fish. They came closest to the surface (between zero and four meters deep) in the afternoon, when the sun was hottest, possibly to increase your body temperature.

First author Emily Spurgeon, a former master's student and current research technician on Lowe's team, relates: “We showed that juveniles directly altered their vertical position in the water column to remain between 16 and 22°C, and if possible between 20 and 22 °C”. This may be your optimum to maximize growth efficiency within the nursery.”

The results showed that the temperature distribution in these waters is always changing, meaning that juveniles have to be constantly moving to stay within this optimal range. The authors concluded that juvenile great white sharks spend most of their time in much shallower waters than adults. The latter were rarely observed in the nursery.

The results also showed that the three-dimensional temperature distribution strongly impacted the horizontal distribution of juveniles, which spread to greater depths when seafloor temperatures were higher and moved closer toward the surface when deeper waters were warmer. cold

What researchers don't yet know is what benefits puppies and young people gain from gathering in daycare centers. An advantage could be avoiding predators. “Our results show that water temperature is a key factor attracting juveniles to the study area. However, there are many locations along the California coast that share similar environmental conditions, so temperature is not all history. Future experiments will look at individual relationships, e.g. to see if some individuals move between nurseries in tandem“concludes Spurgeon.