Nicolas Ziani, scientific manager of the Phocaean Group for the Study of Sharks, closely studied the last days of the female shark baptized Sharkinette a year ago in Hyères. Struck by the similarities with the specimen that has just caused panic in Spain, he explains to us.
The video has been circulating on social media since Thursday. It must be said that the images are frightening: a few meters from Aguamarina beach, in Orihuela Costa, in the Alicante region of Spain, a two-meter-long blue shark seems like crazy among panicked bathers. The animal was found dead, stranded, a few hours later.
Nicolas Ziani, founder and scientific manager of the Phocaean Group for the Study of Sharkswas alerted by one of his students whose work, co-directed by the‘Institut OSU-Pythéas at the University of Aix-Marseille, focus precisely on the causes of mortality of blue sharks in the Mediterranean.
The similarities of the Spanish case with the fate of “Sharkinette”, the female shark who wreaked havoc last summer on the famous Almanarre beach in Hyères (Var), are disturbing. Nicolas Ziani has closely studied this Var case, which helps him today to understand this new episode.
How do you analyze the images of the Alicante shark?
Nicholas Ziani: We see a shark swimming close to the edge, but in a completely dysfunctional way. His swimming is anarchic, it makes no sense. The shark swims in zigzags and circles. He is not interested in swimmers he does not even see. What I see is that the shark’s directional organ, the brain, is disconnected. This is what I call an “undead” shark.
What common points are there with the female observed during the summer of 2022 in Hyères?
Nicolas Ziani : Sharkinette, it was in July, therefore at the same period, reproduction period of the blue shark species. The animals come to the edge of the coast to feed, and -for the females-, to give birth.
In both cases, there was an episode of disordered swimming and a death that was not sudden.
Do these similarities allow you to formulate hypotheses?
Nicholas Ziani: Several explanations are possible. First, the Alicante shark may have fallen victim to a pathogen. There are cases of meningitis in sharks, by bacteria of the type Vibrio which liquefy the brain. The sensory and cerebral functions of the shark are affected, the animal will die, but not immediately. It happened last year to a Greenland shark stranded in England.
But I would rather lean towards the behavior of an animal that has suffered a trauma. There may be interactions with other territorial fish, such as tassergals, which can measure up to two meters and be more aggressive than sharks. Or even the stingrays. They have poisonous stings which they only use to defend themselves against sharks – not on humans! It can also be a collision with a jet-ski or a boat.
What I think I see in any case is that the shark’s directional organ, its GPS, the brain, tripped following a collision whose nature we do not know since there was no autopsy. The shock probably caused a cerebral hemorrhage. It is that which caused the death of the animal after an episode of swimming during which it saw nothing and no one, since the sensory organ was disconnected.
This is also the hypothesis that I favor for Sharkinette. Its death is believed to have been caused by interaction with other fish. Our findings should be published shortly.
Meningitis, or collision, are these frequent causes of death?
Nicholas Ziani: These are not frequent cases but they are poorly known. They are very much in the minority compared to accidental captures. The latter cause 90% of blue shark deaths. The species of blue sharks is critically endangered in the Mediterranean for this reason. In most cases, sharks caught accidentally by longliners are released into the sea, but they are already asphyxiated, and are found directly stranded. More and more fishermen are aware of this issue, but the equipment used is not suitable for targeted capture.
What should you do when you find yourself near a shark with abnormal behavior at the seaside?
Nicholas Ziani: It is better not to stay near the animal. You have to get out of the water quietly, without panic. The Alicante shark would not have bitten, we can clearly see that the motor functions were disconnected, he would not have had the use of his jaw. We can also warn the Phocaean Group for the Study of Sharks, this will be very useful for our work.
Nicholas Ziani: I also want to remind you that a fin does not mean that it is a shark. It maybe a marlin, a Mediterranean lancer like only a few days ago in Antibes. It can also be a swordfish, a sunfish, or a dolphin if you are not familiar with it. In any case, it is better to move away!
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