Since the end of November, an unusually large number of sharks have been sighted off the coast of Israel. They are attracted by an unnatural phenomenon.
Image: picture-alliance/dpa/Hagai Nativ/Morris Kahn Marine Research Station-University of Haifa
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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? Image: picture-alliance/AP Photo/A. Schalit
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 laboratoryImage: picture-alliance/dpa/Hagai Nativ/Morris Kahn Marine Research Station-University of Haifa
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.
For the love of sharks
Image: CC BY 4.0/Albert kok
Sharks, sharks everywhere
Blame it on Jaws or blame it on the fact that sharks do have rather a lot of sharp teeth, fact is, many humans have a fear of sharks as deep as the waters in which they swim. Any expert will tell you, we kill by far more of these great fish a year than they do us. So should we really be scared?
Image: Pterantula (Terry Goss) via Wikimedia Commons
The reef shark
There are five species of reef shark, of which this is one. Feasting on crustaceans and fish alike, they are the top predator in the fragile ecosystem from which they take their name. They are no strangers to divers either, and have been known to attack when they feel threatened.
Image: CC BY 4.0/Albert kok
All shapes and sizes
There are more than 250 recorded species of shark in the waters around our planet. They range in size and ferocity. The sand tiger shark weighs up to 159 kilos and can reach a length of 3.2 meters. They are big eaters, have a mouth full of frightening looking teeth, but are generally regarded as being docile and unlikely to attack humans unless provoked to do so.
Image: picture-alliance/dpa/S.Sauer
Mass slaughter
Though it is impossible to know exactly how many sharks are killed annually for their fins, some estimates put the number around 100 million. Finning, as the practice is known, entails the removal of the fin while the shark is alive. The animals are then cast back into the sea where if not dead already, they succumb to a painful end. The fins are used to make soup, which costs up to $100 a bowl.
Image: Gerhard Wegner/Sharkproject
Growing old gracefully
Recent research revealed that Greenland sharks can live to the extraordinarily ripe old age of 400. These predators have a healthy appetite, but have never been known to go for humans. They like cold waters, through which they move slowly. And that is not the only thing they do at a leisurly pace - they don't even reach sexual maturity until they are around 150.
Image: picture-alliance/dpa/Oceans Image
Just because it's big, doesn't mean...
...it will hurt you. At 18 meters, whale sharks are the longest species in the family, and indeed the biggest fish in the sea. At that rate, dinner should be theirs for the picking, but their penchant is for plankton. Good news for all the other creatures in the sea. But whale sharks are at risk. Not only are they fished for their fins, oil and meat, but are often hit by eco-tourism boats.
Image: CC BY 2.0/Derek Keats
Lemon sharks
Said to be the best researched sharks, the lemon species is considered non-agressive. To date there have been no recorded incidents of a human fatality as a result of a lemon shark attack. They are social creatures that move in groups, where they rarely display aggressive behavior to each other.
