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When a dead thresher shark spilled onto the coast, it was obvious what killed it: a swordfish stabbed him from behind and left a large chunk of his “sword” stuck in the beast, according to a new study.
Nobody saw the actual attack, so it’s not clear why the swordfish hit the shark. But the two ocean predators may have been competing for prey, the researchers said.
“The most likely scenario is that both species hunted on a shoal of fish or squid in the depths,” said study lead researcher Patrick Jambura, a doctoral student in the University of Vienna’s Department of Paleontology.
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It is also possible that the two ocean predators were fighting for territory, or that the swordfish accidentally stabbed the thresher shark and left nearly 12 inches (30.1 centimeters) of its “sword” in the victim, he said.
News of the deadly aftermath of the fight spread when the shark’s body was washed up on Libya’s Mediterranean coast near the town of Brega in April 2020. A group of local citizen scientists learned of the photos and video caught of the 14.5-foot (4.5-meter) long dead shark, and after seeing the evidence “I was just stunned for a few moments,” Jambura told Live Science in an email. Swordfish (The sword xifia) are known to defend against blue sharks (Prionace glauca) and mako sharks (Isurus oxyrinchus), as these sharks prey on swordfish.
Swordfish has also been reported to attack whales, sea turtles, inanimate objects, including boats and submarines, and even the human beings, Wrote Jambura and his colleagues in the study. In 2015, “a diver was killed in Hawaii when he pierced a small swordfish that had entered a marina, “said Yannis Papastamatiou, a marine biologist at Florida International University who was not involved in the study.” He pierced him in the chest. “
But thresher sharks (Alopias superciliosus) eat small fish “and it wouldn’t be a threat” to swordfish, Jambura said.
Whatever the reason for the stabbing, “we know the swordfish attacked from above – the shark most likely was not even aware of the danger. [it] was in until it was too late, “Jambura said. It appears that the approximately 10-foot (3.1m) long swordfish stabbed the shark just behind the head, leaving a 2-inch (5cm) deep cut and 3 inches (8 cm) deep where it punctured the shark’s gill system. As no one has performed an autopsy (an autopsy on animals), there is no way to know if this caused any damage deep internal, “but from the angle and depth of penetration, it’s safe to say that the gill region has been severely damaged, possibly some important arteries as well,” Jambura said.
Although this is the first reported case of a swordfish killing a thresher shark, scientists don’t know how often this happens in the depths of the water. “We rarely see evidence of these findings: sharks are negatively buoyant and will sink when they die,” Papastamatiou told LiveScience in an email. “Unless they wash up on the beach like here (which is rare, most will sink into the deep sea), we won’t find evidence of the interaction.”
The swordfish left the altercation physically damaged, but that doesn’t mean the fish is dead; there are known cases of billfish (a close relative of the swordfish) that have damaged, malformed or even lacked a rostra (or its pointed “sword”) that “apparently were still in good physical shape,” the researchers wrote in the study. . Maybe the attacker survived.
The study was published online Oct.7 in the journal Ichthyological research.
Originally published in Live Science.
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