Jellyfish plague clogs Mediterranean

September 1, 1995

The Levant coastline, stretching from Egypt to the Syrian/Turkish border, boasts some of the best beaches in the Mediterranean. Gently sloping shorelines, clear skies, deep sand, warm waters, hot sunshine . . . and jellyfish, lots of them.

This summer, the huge numbers of one particular kind of these wispy invertebrates have broken all records, providing a mixed blessing for the peoples of the region and an example of the ecological impact of man-made waterways.

Making its debut in the Mediterranean in 1977, the culprit was first identified by Bella Galil from the Israel Oceanographic and Limnological Research Centre as a Lessepsian migrant from the Red Sea and one of more than 300 species to swim to the Mediterranean via the Suez canal.

Rhopilema nomadica can grow up to a metre wide and, in the absence of natural enemies, its population has continued to increase unchecked.

Shoals reported this year have been several kilometres long, 0.5 kilometre wide and 20-30 metres deep with maximum densities of 25 animals per cubic metre.

Masses of the jellyfish have clogged fishing nets, spoilt catches, and obstructed cooling water intake pipes at power stations. Tourism has also been affected as the jellyfish have a sting, the severity of which can range from a burning sensation to the appearance of fluid filled blisters on the skin.

However, on the plus side, R. nomadica is edible and has certain medicinal properties that could make it something of an economic windfall for struggling local fishing communities. Trial batches have already been sent to several Far Eastern states for assessment and it is hoped that the current shortage of jellyfish in Japanese and Korean waters will help to boost sales.

Many of the behavioural features of the jellyfish remain unknown, and Dr Galil stresses the need to continue studying it, in particular its effect on the wider Mediterranean ecology and its impact on the food chain.

"This is a classic case of a species invading a new environment and finding a niche where it can multiply rapidly. More studies need to be carried out to determine the likely effect of such large numbers of this species on the local ecosystem," he said.

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