At the start of July 2025, it is time to review jellyfish sightings for June, marking the beginning of the summer season.

As every year, jellyfish are already present along our coasts, with successive waves in the Mediterranean and Atlantic. The situation varies by region and species.

First arrivals in the Mediterranean

In the Mediterranean basin, the first half of June 2025 saw an early wave of Pelagia noctiluca (the mauve stinger) from Marseille to Saint-Tropez, accounting for up to 60% of regional reports. From the third week, the Nice/Antibes area experienced a significant rise, with the Côte d’Azur reaching nearly 40% of Mediterranean sightings before declining at the end of June. Corsica remained relatively spared this year (~10% of Mediterranean reports), unlike in 2024 when the island saw a peak of nearly 30% at the same time.

The Armorican episode

As almost every year, mid-June brought a wave of compass jellyfish (Chrysaora hysoscella) to the Atlantic, especially in the Bay of Biscay. In 2025, this event was more pronounced than in 2024, accounting for up to 20% of national reports in mid-June, but less intense than in 2023 when both duration and scale were exceptional. Occasional strandings of Physalia physalis (Portuguese man o’ war) were also reported, mainly on the Basque coast.

Observed species

  • Pelagia noctiluca (mauve stinger): dominant in the Mediterranean, small, violet, and stinging.
  • Chrysaora hysoscella (compass jellyfish): frequent in the Atlantic, recognizable by its brown radial stripes.
  • Rhizostoma pulmo (barrel jellyfish): occasionally seen on the Côte d’Azur and Corsica, large and mildly stinging.
  • Physalia physalis (Portuguese man o’ war): rare but monitored in the Atlantic, potentially dangerous.

Regional comparison (share of reports, June 2025)

Region% of reportsMain species
Mediterranean (excluding Côte d’Azur) ~45% Pelagia noctiluca
Côte d’Azur ~35% Pelagia noctiluca, Rhizostoma pulmo
Corsica ~10% Pelagia noctiluca, Rhizostoma pulmo
Atlantic ~10% Chrysaora hysoscella, Physalia physalis

Animated retrospective

Below you will find an animated video showing the arrivals of jellyfish on the coasts, with color coding by species. Data for June 2023 and 2024 are also available in the following slides for comparison.

In this first month of the summer season, Meduseo publishes the ranking of towns most affected by jellyfish in July 2023. In July, beaches in France, Spain and Italy were hit by a significant presence of jellyfish, affecting bathing in certain regions. In France, Bonifacio in Corsica was the worst affected, with 18 days of jellyfish, while in Spain, Ciutadella de Menorca topped the list with 21 days. In Italy, Cervia recorded 10 days with jellyfish, making it the worst affected town in the country. The coastal regions of Corsica, the Côte d'Azur, Menorca, the Adriatic, Puglia, Sardinia and Sicily were mainly affected.