Juvenile Great White Sharks Prefer Warm, Shallow Water Close to Shore, Study Finds

Marine scientists have discovered that baby great white sharks aggregate in shallow, warm waters within one kilometer of the coast.

Nurseries For Baby Great White Sharks

The findings were noted in the "The influence of micro-scale thermal habitat on the movements of juvenile white sharks in their Southern California aggregation sites" study. They are crucial for significant white shark conservation as ocean temperatures rise due to climate change. The findings are also critical for the public's protection against negative shark encounters.

After their birth, baby great white shark pups do not receive maternal care. In a population studied off Padaro Beach in central California, juveniles and pups appear within nurseries without adult company.

Dr. Christopher Lowe, the study's senior author and a California State University professor, says this is one of its most detailed and extensive diets. Surrounding this beach, many juveniles share habitats near shore. Because of this, it is possible to learn how environmental conditions could influence their movements. The professor explains that it is rare to witness such nursery behaviors among great white sharks in other areas.

Back in 2020 and 2021, the Lowe team used darts to tag 22 juveniles with sensor-transmitters. The sharks were male and female, ages one to six years. The transmitters gauged real-time local water pressure and temperature. It also monitored the position of each juvenile by releasing acoustic pings into a receiver array. These were spread out across the shoreline, over around 5.5 square kilometers. Such methods have gained the approval of the University's Animal Care and Use Committee and the Department of Fish and Wildlife of California.

Tracking was halted during winter months when juveniles temporarily left offshore waters. The scientists gathered more data on temperature distribution across the local water columns with the help of an autonomous underwater vehicle. The researchers then used artificial intelligence to train a 3D model of the juveniles' depth preferences and temperature.

Findings revealed that around dusk or dawn, juveniles entered greater depths. The sharks may have been foraging on rays, skates, schooling fish, and other kinds of small bony fish. When the sun was hottest in the afternoon, they neared the surface, with depths ranging from zero to four meters. This was possible to increase their body temperatures.

Emily Spurgeon, the study's first author, former master's student, and present research technician in the Lowe team, shares that they showed that the juvenile sharks altered their vertical position directly in the water column to stay between 16 and 22 degrees Celsius. If possible, they did so between 20 and 22 degrees Celsius. This could be their optimum for maximizing growth efficiency in the nursery.

Shallow Waters

Findings show that in these waters, temperature distribution is widely changeable. This means that juveniles must constantly move to stay in this optimal range.

The results also revealed that temperature distribution throughout three dimensions strongly affected the juveniles' horizontal distribution.

What remains unknown is the benefits that juveniles and pups gain from nursery gatherings. It is possible, however, that predator avoidance could be an advantage.

Spurgeon explains that the findings show that water temperature is crucial to drawing juveniles to the study area. However, several regions of the California coast have similar environmental conditions. Hence, temperature is not the entire story. Further experiments will examine individual relationships to see if some individuals move in tandem among nurseries.

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