VALENCIA – Dead sharks washed up along the Spanish coast are puzzling scientists. Last week, a blue shark washed ashore near Benidorm. The same shark previously cleared a crowded beach.
That disoriented shark had been examined by scientists and returned to the sea. On Sunday, August 22, the shark washed ashore dead in the municipality of El Campello. According to the necropsy by the Department of Marine Zoology of the University of Valencia, the cause of death is believed to have been a small wound under the eyelid. According to the researchers, that wound is compatible with a swordfish attack.
The relatively unknown aggression between the sea creatures sparked the curiosity of scientists who started an investigation into the relationship between them. In 2016, Valenica recorded the first case of a fatal shark attack by a swordfish.
Tests showed a fragment of an 18-centimeter swordfish knife in the shark’s brain. This aggressive interaction between a juvenile swordfish and blue sharks in the Western Mediterranean stunned the researchers. Since then, similar encounters have been recorded in Italy and Libya.
Attacks target shark head
In June 2019, another five attacks were documented. Since then, new attacks have been discovered and will soon be recorded. The attacks appear to follow a similar pattern, targeting the shark’s head. From this, the researchers conclude the swordfish is acting deliberately.
There is still too little data available to know whether attacks occur on other parts of the body and whether it concerns aggression from the swordfish or actions in self-defence. Because swordfish are smaller than blue sharks, the researchers believe there is a good chance that the swordfish will defend themselves in this way.
Why the new aggression?
The fact no one has paid attention to it until now may be a reason that this type of aggression is now more often detected. One of the researchers in El País indicates that there may be another cause that is causing the attacks, such as global warming or seawater. This is a hypothesis as there is no data to confirm it.
There are, however, numerous scientifically known cases of swordfish attacks on turtles, whales and small boats. But clashes between swordfish and sharks only appeared in storybooks; until now. There are stories of fishermen who encountered sharks with their heads impaled by a sword.
Other biologists think the attacks are accidental and occur during the hunt. Where there are schools of fish, all predators try to catch what they can. Swordfish then swing their sword to hit the small fish which, once stunned, will be eaten. Accidental collisions can occur in this chaos.
Also, there would be little motive for an attack against a shark by a swordfish. They do not fight for the same habitat, because they are migratory animals. They also don’t have to defend their young because their maternal duties end once the eggs are laid. Nor does one animal see another as prey. Until more cases are found, the mystery is not yet solved.