Naama Barak
July 13, 2023

In great news for anyone trying to enjoy their summer vacation, Israeli beachgoers can look forward to a relatively jellyfish-free sea this coming season, according to researchers at the University of Haifa.

Unlike recent years that saw huge swarms of jellyfish along Israel’s coast in July, right now beaches are pretty clean of jellyfish – an indicator that might just mean the invasions we’ve become accustomed to might not materialize. 

“Based on previous years, when the jellyfish arrived late, we had small summer swarms, and it is possible that we will see such a phenomenon this year as well. That is, we will not get a large and dense swarm,” said marine macro ecologist Dor Edelist.

“We say this cautiously, and of course the reality can still change. But if you look at the past cases, this estimate is reasonable as of this moment,” Edelist said.

“In previous years, we would receive reports at this time of the summer from yachtsmen and other sea travelers that the jellyfish were on their way to us,” added applied marine ecologist Prof. Dror Angel. “This year, they are also saying right now that the sea is free of jellyfish.”

Aerial studies confirm this suspicion, added Gur Mizrahi, who studies jellyfish migration patterns.

“The area we surveyed from the air was very wide,” Mizrahi noted. “We flew 10 kilometers from the shoreline and along all the beaches, and no swarms of jellyfish were observed. We saw a few jellyfish that may have remained in the area from the winter and spring periods.”

According to the researchers, climate change caused sea water to warm more slowly this year, leading to a delay of two weeks in the jellyfish’s reproduction and migration to Israel’s shores. This, however, does not completely explain their lack of appearance by now.

“It is possible that … another factor influenced the picture on their migration, for example, animals preying on jellyfish when they are small. Of course, other things may have occurred, because the sea is a complex and complicated system,” Angel said.

Angel cautioned, however, that “if anyone thinks that this is the end of jellyfish, they are wrong. What happened this year does not say anything about the population of jellyfish that sit on the seabed, when they are still in the polyp stage, prior to sexual maturity and reproduction.”

These polyp colonies are waiting for the right conditions to hatch and release mature jellyfish into the sea. 

“So, according to everything we know now, the jellyfish really aren’t going to disappear,” he concluded. “This year is just a slight hit under the wing for them.” 

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