Swimmers in northern Spain surprised by aggressive mini-jellyfish

by Lorraine Williamson
aggressive jellyfish

LAREDO – In the north of Spain, particularly on the beaches of the Cantabrian Sea, swimmers and authorities have been alarmed by a sudden invasion of small, aggressive jellyfish, known as the Portuguese Man o’ War. 

The summer months in Spain are traditionally associated with sun, swimming in pools, and beaches. Unfortunately, not everything is always positive. Alongside nuisances such as parking problems or crowded terraces and restaurants, another concern may arise: jellyfish. 

Unknown species surprises swimmers 

The Portuguese Man o’ War (Physalia physalis), distinguish themselves by their unique small shape and dark colour, unlike most other jellyfish species commonly found along the Spanish coasts. Furthermore, these jellyfish have been spotted along the Cantabrian coast in seaside resorts such as San Sebastian. 

A video published by @diariovasco on TikTok shows the Portuguese Man o’ War and explains their appearance and behaviour. The footage displays some dead specimens that have drifted to the Cantabrian coast from neighbouring Portugal. This was most likely due to ocean currents and rising sea temperatures. 

Particularly Dangerous 

What makes these jellyfish especially dangerous is their ability to sting in an unusually virulent manner, even after death. Their stings are always painful and unpleasant. Although some tricks can alleviate the pain, this particular species can be especially harmful. 

Consequently, the authorities of the Basque Country have urged swimmers to be extra cautious when entering the sea to avoid being stung by these potentially harmful jellyfish. 

Protocol in San Sebastián 

However, the city council of San Sebastián has relaxed the protocol for dealing with this species of jellyfish on beaches. Moreover, they do not want to unnecessarily restrict swimming. 

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The new protocol provides for four different scenarios, each with its own action plan: 

If fewer than 15 specimens of Portuguese Man o’ War are detected on the beaches of La Concha and Zurriola, and fewer than 10 on Ondarreta, a yellow flag will be raised. This means that swimming is advised with caution, but not prohibited. 

Only when these numbers are exceeded will the red flag be raised, meaning that swimming is prohibited. 

If someone is stung, but no other specimens are spotted and the one that stung has been removed, swimming will not be prohibited. Instead, a yellow flag will be raised, indicating that swimming is advised with caution. 

In all cases, a flag bearing the logo of jellyfish will be raised, and through the beach’s loudspeakers, people will be informed of the specific situation at that moment. 

The city council has emphasised that there will be regular follow-ups on the situations, and the flags can be adjusted to previously established criteria. Checks will be made every two hours but may occur more frequently if needed. 

Also see: Carefree swimming in Spain without jellyfish? Do the check! 

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