Poisonous ‘Portuguese men o’ war’ invade Caparica beaches

Seasonal tides have brought an ‘invasion’ of jellyfish – including the poisonous ‘Portuguese men o’ war’ that trail long tentacles, able to kill a fish with just one sting, and cause unpleasant reactions in people.

These much-feared sea creatures are often sighted on west coast beaches around Lisbon / Costa Caparica. But this year they’ve become something of a scourge – with local authorities promising a clean-up operation along affected beaches (see update below).

The point to remember about jellyfish in general, and Portuguese Men o’ War in particular (which are not technically jellyfish, but much more unpleasant ‘marine hydrozoans’) is that they can still pack a punch when lying, apparently lifeless, on the sands.

They’re much more dangerous in the sea, thus anyone swimming has to be vigilant.

The advantage of spotting a jellyfish – or a marine hydrozoan – ahead, beside or even behind you, is that swimmers always have the chance to ‘get away’: jellyfish et al bob/ ‘go with the flow’. They cannot swim towards prey, or launch attacks.


Sea and atmosphere institute IPMA has announced that Portuguese Men o’ War have now been sighted throughout national territory, including along the beaches of Azores and Madeira.

In an announcement warning people of the dangers, IPMA refers anyone who sights a Portuguese Man o’ War to update information on the GelAvista Facebook site, designed to involve citizens in science.

And in the unhappy case of contact with one of these creatures, there are four points to remember: remove any pieces of tentacle that may remain stuck to the skin, wash the affected area abundantly with sea water, NOT with fresh water, only apply ice that is wrapped (ie avoid contact with skin), and seek medical assistance.

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Image: a ‘typical jellyfish’ (called ‘alforreca’ here) often sighted on national beaches, not a Portuguese Man o’ War