In the colder winter months, sometimes 50 to 100 sharks cavort in the shallow water off the coastal town of Chadera, some 50 kilometers north of Tel Aviv. Such a large population of sandbar sharks and dusky sharks is rare to see, says marine researcher Ejal Bigal, who has been studying for four years what the animals are doing in the eastern part of the Mediterranean Sea.

In the last 100 years, 95 percent of Mediterranean sharks have been exterminated, Bigal said. Since they prefer shallow water near the coast, they are caught faster by fishermen. In addition, sandbar sharks (Carcharhinus plumbeus) reproduce late - often after 20 years. It is all the more astonishing to see so many specimens of this endangered species in one place.

Does the warm sewage from the power plant attract the sharks?

They are apparently attracted by warm water pumped into the sea from a nearby power plant, said the scientist from the University of Haifa. That's where the sharks congregate.

"In the middle of the Jacuzzi," Bigal jokes.

A wealth of fish also possibly attracts the hunters to the area. Each year different sharks come. Bigal knows this because he has already equipped 41 animals with sensors to track their movements. Two sandbar sharks had already been in Chadera two years ago, the others were newcomers.

For some time now Bigal and his research colleagues have been collecting blood and tissue samples along with ultrasound images of the animals. The research possibilities in this "laboratory in the middle of nature" are ideal. The researchers can examine the animals in shallow water without having to pull them out of the sea.

Scientific investigations in the natural laboratory

However, the shark spectacle also attracts numerous divers. The sharks can even be seen from the beach with the naked eye.

"It won't be possible to prevent shark watching," says Bigal. But he also sees it as a chance to enlighten people. After all, sharks are enormously important for the ecosystem because they eat sick marine animals and control populations of other species.

The Israeli scientists assume that they will continue to feed the sharks until May. History shows that the animals then migrate back to cooler waters.