Bull Shark Population on the Rise Due to Global Warming [Study]

Bull Shark Population on the Rise Due to Global Warming [Study]
(Photo : Pexels/Berthold Grünhagen)

Not all animal species suffer from global warming. Researchers learned that at least one marine species thrives with the increase of the sea surface temperature.

Bull Sharks' Population Increase Amid Global Warming

According to a new study, the number of bull sharks, one of the most aggressive species of shark worldwide, has increased in the last 20 years, and warmer seawater is to blame.

The species is normally found in warm, shallow coastal waters in both fresh and saltwater habitats, which is why they thrive while other species have started to decline, per Lindsay Mullins, a Ph.D. student at Mississippi State University's Wildlife, fisheries and aquaculture department and lead author of the study.

Increasing sea surface temperatures over the past 20 years have coincided with a five-fold increase in the abundance of juvenile bull sharks in Mobile Bay, an estuary in Alabama. Bull sharks are among the shark species most likely to have a negative interaction with humans, along with the great white shark and the tiger shark.

Using information from 440 bull sharks caught and released during surveys carried out between 2003 and 2020 by the Alabama Department of Conservation and Natural Resources, which has been conducting a gill net survey of the Alabama coastline, researchers were able to measure changes in the distribution and abundance of bull sharks in Mobile Bay, according to Mullins.

The report states that environmental elements related to these changes during the same period were gathered using data from remote sensing. The results demonstrated a five-fold rise in the number of individual sharks recorded per hour of surveying between 2003 and 2020. Furthermore, during the study period, every bull shark surveyed was a youngster.

The article states that the increase in population was accompanied by a rise in the mean sea surface temperature in Mobile Bay, which increased from 22.3 degrees Celsius (72.1 degrees Fahrenheit) in 2001 to 23 degrees Celsius (73.4 degrees Fahrenheit) in 2020.

The researchers discovered that data generated by computer modeling was linked to a higher probability of bull shark occurrence at sea surface temperatures exceeding 22.5 degrees Celsius.

The study also showed that, despite increased coastal urbanization since 2000, the average probability of capturing a bull shark during surveys increased throughout Mobile Bay between 2003 and 2020. The western bay shoreline and the vicinity of Daphne were the most likely places to tag a bull shark.

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How Aggressive Is a Bull Shark?

Shark biologist and conservation lead at the Australian Marine Conservation Society, Leonardo Guida, Ph.D., said bull sharks are an aggressive species. She warned anyone approaching them to use caution.

Bull sharks are also thought to be the most harmful to people due to their aggressive nature and capacity to move up rivers. Bull sharks also favor shallow coastal waters, which increases the likelihood that they will interact with people.

In February 2023, a bull shark attacked an Australian adolescent girl who was swimming with dolphins, resulting in her death. Stella Berry, 16, spotted a pod of dolphins and decided to swim with them while she was with her pals on the banks of the Swan River in North Fremantle, Perth. However, a shark bit her leg and it was later identified as a bull shark.