Jellyfish forecasts for the French Riviera


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"At first we'll see some light breezes to the south, picking up towards midday, followed by some scattered showers, and a plague of jellyfish stinging everything in sight in the early afternoon…"

The coasts of the French Riviera have employed an early warning system for jellyfish, due to ongoing issue with stinging.

In some cases, up to 500 people in one day have been stung by Pelagia noctiluca, or the Mauve stinger to give it a more sinister name. These jellyfish have a history of misdemeanors, and back in 2007 a swarm of billions of them wiped out over 100,000 salmon at a farm in Northern Ireland.

Current measures include anti-jellyfish nets, but these only have a limited effect. Through a suspected combination of rising temperatures and a depletion of natural predators, numbers have proliferated, and the waspish inverts are still finding their way inshore.

Now, to try to get on top of a wave of irritated bathers, the oceanological institute of Villefranche-Sur-Mer is launching a 48-hour forecast, predicting jellyfish numbers before they become a problem.

The forecasts are based around an observed link between the breaching (the shore invading behavior) and winds and currents.

By way of warning, a five point probability rating is to be employed, going from a grading of zero, at which there is no jellyfish risk, up to a five rating, classed as the maximum jellyfish likelihood.

The increase in numbers is not a local phenomenon, and Practical Fishkeeping has reported on swarms of jellyfish cluttering up cooling ports in power stations around the world.

Without a change to either the environmental conditions favourable to them, or an rapid increase in levels of natural predators — chiefly Tuna and turtles — the problem looks set to get worse over coming years.

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