Sharks and humans sharing waters along California coast more often than previously thought
A team of biologists at California State University Long Beach has found that sharks and humans are sharing the waters along California's shore much more often than previously thought. In their study, reported in the open-access journal PLOS ONE, the group analyzed hundreds of hours of video captured from drones flying just off the coast of multiple beaches in California.
When sharks attack or bite humans, it tends to make the news. But this is because it happens so rarely, especially considering how many people venture into the ocean. In this new effort, the research team wondered if the low numbers of shark bites along California's shores is due to few interactions between sharks and people or reluctance by sharks to bite.
To find out, they deployed drones over 26 California beaches where people are known to swim over the years 2019 to 2022. In so doing, they amassed over 700 hours of footage. They then studied the video imagery, noting times when sharks and humans were on or in the same waters.
In looking at their video, the research team found that humans and sharks were near one another more often than previously thought. They found, for example, that 97% of the time when a person was in the water at the two most popular beaches, there was a shark nearby. In most instances, they were white sharks, which are not known to be aggressive toward humans.
The researchers also found that the sharks, most particularly juvenile sharks, tended to swim much closer to shore than previously thought, oftentimes venturing to within 50 to 100 meters from the beach. They also found that when sharks and humans were in proximity, the human did not appear to know that the shark was there.
The researchers also found that there was only one account of a shark biting anyone in the areas where they were filming over the period of their study—and just 20 since 2000. They note that numbers did not appear to be rising despite more people venturing into the ocean along California's coast and rising numbers of sharks living in the area due to warming ocean temperatures.
More information: Patrick T. Rex et al, Patterns of overlapping habitat use of juvenile white shark and human recreational water users along southern California beaches, PLOS ONE (2023). DOI: 10.1371/journal.pone.0286575
Journal information: PLoS ONE
© 2023 Science X Network