Shark alert in Caddebostan! Will a shark attack the shore?

With the warm weather in Istanbul, residents flocked to beaches to cool off. A shark that came ashore on Caddebostan Beach in Kadıköy caused panic. After spotting the shark, residents rushed to the shore and alerted the coast guard. Authorities warned residents to remain vigilant.

WHY DID THE SHARK COME ABOVE?

Experts stated that sharks are coming ashore in the Sea of Marmara due to oxygen deficiency. Sharks constitute 536 of the 1,282 species of cartilaginous fish in the world.

In Türkiye's seas, 90 percent of cartilaginous fish species are in the Mediterranean, while more than 50 percent are in the Aegean Sea. There are 25 cartilaginous fish species in the Marmara Sea and 11 in the Black Sea.

Because cartilaginous fish have very fast metabolisms, their oxygen needs are very high. Dr. Hakan Kabasakal, WWF-Turkey Cartilaginous Fish Advisor, stated that sharks come ashore due to oxygen depletion in the Sea of Marmara. Highlighting the oxygen levels in the Marmara Sea, Kabasakal said, “One liter of seawater requires at least 4.5 milligrams of oxygen to survive under normal conditions. Today, dissolved oxygen levels in the deep Marmara Sea have fallen below two milligrams in many areas. In fact, some areas have dropped below one milligram from depths of 100 meters. In Eastern Marmara, beyond the continental shelf, there are areas with zero oxygen at depths of more than 200 meters. The combined effects of both pollution and climate change have led to a decrease in oxygen levels in the Sea of Marmara, especially in deep bottom waters, and to a mass migration of cartilaginous fish seeking suitable habitats to coastal waters.”

ATTACKERS?

Kabasakal stated in his statements that cartilaginous fish species coming closer to the shores to survive do not pose a threat to humans.

Kabasakal said that the aggressive species left Türkiye about 40 years ago and continued:

Some shark species considered aggressive, such as great whites, left the Marmara Sea 40 years ago. The sharks that approach the shores are generally called "snow sharks," which measure up to two meters in length and are wary of humans. These species, rushing to shore in search of a place to live, are particularly targeted by coastal fishermen. During our research over the last three years, we observed peak populations near the coast. By 2024, we observed this population plummeting. In other words, there are no longer as many sharks or cartilaginous fish in the coast. The cartilaginous fish you see on the shore are unable to return or find peace in their new migration areas due to the continuing lack of oxygen in the bottom water. These regions are also under intense fishing pressure. One-third of the 1,266 species living in the oceans will become extinct before the end of this century if conditions remain unchanged. The biggest cause of this threat is overfishing. Other causes include habitat destruction, climate change, and marine pollution.

Cartilaginous fish species play a crucial role in maintaining the healthy functioning of the food pyramid. If the balance between all ecological transitions created by predator pressure in the marine ecosystem is disrupted, the entire ocean food landscape could collapse.