In what can only be described as surreal underwater life, scientists believe they have identified the primary suspects involved in the disappearance of a pregnant porbeagle shark that was discovered off the coast of Bermuda.
the culprit? Either a Great white shark Or, less likely, a Make a shortfin. If confirmed, this would represent the first recorded case of shark-on-shark violence with a species of this size.
Lead author of a study published in Frontiers in Marine ScienceBrooke Anderson described the incident as both surprising and disturbing. “This is the first documented poaching incident Porbeagle shark anywhere in the world,” she said in a statement.
“In one event, the population not only lost a reproductive female that could have contributed to population growth, but it also lost all its developing offspring. If poaching is more widespread than previously thought, there could be major implications for porbeagle shark populations that are already suffering from historical overfishing.”
Porbeagle sharks, native to the Atlantic and South Pacific oceans as well as the Mediterranean Sea, are large, powerfully built creatures that can grow up to 12 feet long and weigh as much as 500 pounds.
These sharks are known for their long lifespans, which can extend to 65 years, and for their slow reproductive cycles. Females do not reproduce until about age 13, and they give birth to an average of four cubs every one or two years.
Because of this slow reproductive rate, porbeagle populations are particularly vulnerable to threats such as overfishing, whether intentional or by accident, and habitat degradation.
The species is currently listed by the International Union for Conservation of Nature (IUCN) as Critical in the Northwest Atlantic and Critically Endangered in the Northeast Atlantic and Mediterranean.
Anderson and his colleagues tagged the pregnant porbeagle involved in the study in 2020 during a research expedition off Cape Cod in Massachusetts. The researchers equipped the shark with two satellite tags: a fin-mounted satellite transmitter and a pop-off site to track its location. Archival tag (PSAT) to monitor depth and temperature.
After its release, the shark was tracked for a total of 158 days, during which it initially displayed typical porbeagle behavior, moving at depths between 300 and 2,600 feet, depending on the time of day. The temperature registered by the tag flicked between 44 and 74 °F.
But on March 24, 2021, the PSAT data revealed a sudden and drastic change. For four days, the tag recorded a constant temperature of 72°F, despite being at a depth of about 500 to 2,000 feet.
The team suggested that this meant the shark had been eaten by a larger predator, which released the PSAT a few days later.
Once the PSAT returned to the surface, it began transmitting data to the team.
The researchers considered two potential predators large enough to prey on adult porbeagles: the great white shark and the shortfin mako shark.
While both species are known to inhabit the area and could potentially prey on porbeagles, the data point to the great white as the more likely culprit. Unlike the shortfin mako, which typically exhibits a rapid, oscillatory diving pattern, the behavior of the great white more closely aligned with data recorded by PSAT.
“The hunt for one of our pregnant porbeagles was an unexpected discovery,” Anderson said. “We often think of large sharks as apex predators. But with technological advances, we’re beginning to discover that large predator interactions may be even more complex than previously thought.
“We need to continue studying predator interactions to estimate how often large sharks prey on each other. These interactions will help us explore what cascading effects can have on ecosystems.”
Do you have any tips on a science story? Newsweek Should there be a cover? Do you have a question about sharks? Let us know by [email protected].
References
Anderson, BN, Horstmeier, L., Ballard, KL, Dodd, J., & Sulikowski, JA (2024). First evidence of predation on adult porbeagles equipped with pop-off satellite archival tags in the Northwest Atlantic. Frontiers in Marine Science. https://doi.org/10.3389/fmars.2024.1406973
Post Shark-on-shark attack ‘unexpected’ solution to marine murder mystery appeared first Newsweek.