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An invasive jellyfish that devastated fish populations in the Black Sea and the Baltic has reached Israel, the Israel Oceanographic and Limnological Research institute said yesterday.

The species, known as the warty comb jelly (Mnemiopsis leidyi), is considered one of the world's most invasive species.

The animals were first spotted off Israel's coast by Dr. Nurit Kress and Professor Bella Galil, and were positively identified by Dr. Tamara Shiganova of the Russian Academy of Sciences in Moscow.

"It came to Israel three months ago, and has spread from Acre to Ashkelon," Galil said.

The warty comb jelly poses no threat to humans. Native to North and South America, it reached the eastern Mediterranean in water carried by ships.

In the 1980s it caused severe damage to the commercial fishing industry in the Black Sea, where it fed on eggs and larvae of other floating species, including anchovy.

In the 1990s the comb jelly entered the Caspian sea, where it depleted the zooplankton population, thus affecting the entire food chain. It also invaded the Baltic sea, where it damaged commercially fished species.

Its spread had been aided by the fishing industry itself, which has depleted the population of the comb jelly's predators. Marine pollution also gives it another food source.

"The discovery of the comb jelly off our shores indicates it can adapt to a very wides range of seas," Galil noted. "It reaches a length of 10 centimeters, and got its name thanks to its bristles. It is hermaphroditic, and each specimen can produce up to 8,000 eggs."

"The Mediterranean has a much more extensive range of species than either the Baltic or the Caspian seas, so the comb jelly would cause less damage here," said Galil. "But it can definitely do some harm. We now have a new predator in the local ecosystem, and the fact that there is already such a significant number of them indicates it is reproducing at the expense of native species."

"The only thing we can do is to tackle the factors that help the comb jelly to spread, such as unsupervised fishing and marine pollution."