In a chilling tale of shark-on-shark crime, a pregnant porbeagle met her tragic end in the waters of Bermuda. Thanks to a satellite tag that had been attached to her, marine biologist Brooke Anderson from Arizona State University was able to unravel the mystery. The data from the tag indicated a sudden increase in temperature at depth, leading to the grim conclusion that the porbeagle had fallen victim to a larger predator.
Porbeagles, also known as Lamna nasus, are formidable mackerel sharks that are facing a troubling decline in numbers. These sharks, which can grow up to 3.7 meters in length and weigh as much as 230 kilograms, are prized targets for both recreational and commercial fishing. Additionally, they often become bycatch in fishing operations, further threatening their survival. The slow reproductive cycle of porbeagles, with females only starting to reproduce at around 13 years of age, leaves them particularly vulnerable to population depletion.
To shed light on the movements and behaviors of porbeagles, Anderson and her team utilized pop-off tags that collect data on temperature, water depth, and location. The pregnant porbeagle, measuring 2.23 meters, was tagged in October 2020, and the researchers began receiving data from the tag in April 2021. The unexpected spike in temperature recorded by the tag on March 24, coupled with changes in the shark’s diving behavior, pointed to a chilling scenario of predation by a larger, partially endothermic shark such as a white shark or shortfin mako.
The discovery of a pregnant porbeagle falling victim to predation sheds light on a disturbing aspect of shark behavior that is rarely observed. The loss of not just one, but potentially multiple sharks in a single incident, raises concerns about the survival of the porbeagle population. Anderson suggests that while the behavior may not be new, it has remained hidden due to technological limitations. By tagging more porbeagles and other shark species, researchers hope to uncover the frequency of such encounters and their impact on shark populations.
The advancement of satellite tagging technologies has revolutionized our ability to study marine species, revealing previously unknown behaviors and interactions. By delving deeper into the mysteries of the open ocean, scientists aim to gain a better understanding of the challenges facing vulnerable species like porbeagles. The tragic fate of the pregnant porbeagle serves as a stark reminder of the hidden dangers lurking beneath the waves and the urgent need to protect marine ecosystems.
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