Scientists Tag 7-Foot Shark, Realize Something’s Terribly Wrong as Strange Readings Come Back
Researchers tracking a pregnant 7-foot porbeagle shark off the coast of Massachusetts made a groundbreaking and disturbing discovery. The shark was equipped with two tracking devices—one that transmits signals when surfacing and another pop-off tag that floats to the surface after about a year. However, the pop-off tag detached and surfaced just 158 days after being attached, indicating an unexpected event.
Initially, the data from the tag showed normal readings, but suddenly, the temperature spiked at a depth of 600 meters, contradicting typical water temperature patterns that decrease with depth. This indicated something had severely gone wrong, leading researchers, including Arizona State University’s Brooke Anderson, to conclude that the shark had likely been eaten.
This incident marks the first documented case of a porbeagle shark being preyed upon, suggesting the presence of a larger predator, such as a great white or shortfin mako shark. The study, published in “Frontiers in Marine Science,” provides new insights into the predation dynamics affecting this threatened species. Scientists eliminated orcas as potential predators due to their higher internal body temperatures, instead hypothesizing that a mature female great white, potentially over 15 feet long, was responsible for the porbeagle’s demise.
Researchers tracking a large shark may have stumbled on a disturbing first-of-its-kind discovery after recovering one of the tags.
The apex predator, a 7-foot pregnant porbeagle shark, was caught by scientists off the coast of Massachusetts in October of 2020 and tagged with two tracking devices.
One of the devices affixed to the fish’s fin was designed to transmit a signal when it broke the surface of the water. The other, called a pop-off tag, pops off after roughly a year and floats to the surface, providing scientists with critical data.
The tags and tracking program aim to discover more about the shark species’ reproductive cycle and to pinpoint where the mothers give birth.
According to NBC News, those watching the shark realized something wasn’t right when the pop-off tag floated to the surface only 158 days after being attached to the shark.
The device held a disturbing record.
Data on the tag reveals the first months were normal, showing depth and temperature readings expected from an active shark. Then, the record took a shocking turn.
“Something had gone very wrong,” Arizona State University shark researcher Brooke Anderson told NBC.
“All of a sudden, the temperature spiked, even at 600 meters depth, and stayed elevated.”
Typically, water grows colder as depth increases. The increase in depth coupled with the relatively high and consistent temperature pointed to a potential reality nobody expected.
The other tag, designed to stay attached to the shark and transmit at the ocean’s surface, has been completely silent.
“All of the data pointed to the same conclusion,” Anderson said. “She had been eaten.”
This is the first report of a porbeagle shark of this size being turned into prey, a feat that seemingly can only be accomplished by a much larger animal.
Researchers published the discovery in the Frontiers in Marine Science journal.
“Given the location of predation and elevated temperature at depth recorded by the pregnant porbeagle’s tag, potential predators include endothermic shark species such as the white shark Carcharodon carcharias and shortfin mako Isurus oxyrhinchus,” the article states.
“This is the first evidence of predation on a porbeagle globally and provides novel insight into inter-specific interactions for this large, threatened shark species.”
Scientists dismissed the possibility that a predatory marine mammal such as the orca had anything to do with the shark’s apparent disappearance.
“Large marine mammals,” the article explains, “such as odontocete whales (e.g., Orcas Orcinus orca) maintain much higher internal temperatures (close to 40°C; Whittow et al., 1974; Strøm et al., 2019) and so were not considered as a potential predator in this instance.”
Anderson’s educated guess is that the porbeagle’s predator is a mature female great white shark, “probably 15-feet plus.”
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