Whodunit solved when 'sword' is found embedded in thresher shark - Livescience.com

When a dead thresher shark washed up onshore, it was obvious what had killed it — a swordfish had stabbed it from behind and left a large hunk of its "sword" embedded in the beast, a new study finds.

No one saw the actual attack, so it's unclear why the swordfish jabbed the shark.

It's also possible the two ocean predators were fighting over 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. .

A local citizen scientist group learned about photos and video taken of the 14.5-foot-long (4.5 meters) dead shark, and after seeing the evidence "I was just stunned for a few moments," Jambura told Live Science in an email.

In 2015, "a diver was killed in Hawaii when he speared a small swordfish that had wandered into a marina," said Yannis Papastamatiou, a marine biologist at Florida International University, who was not involved in the study.

But thresher sharks (Alopias superciliosus) eat small fish "and wouldn't be a threat" to swordfish, Jambura said.

Whatever the reason for the stabbing, "we know that the swordfish attacked from above — the shark was most likely not even aware of the danger [it] was in until it was too late," Jambura said.

It appears that the roughly 10-foot-long (3.1 m) swordfish stabbed the shark just behind the head, leaving a cut 2 inches (5 centimeters) deep and 3 inches (8 cm) wide where it pierced the shark's gill system.

While this is the first reported case of a swordfish killing a thresher shark, scientists don't know how often this happens in the water's depths.