INCREASINGLY WARM WATERS in the Mediterranean are encouraging hundreds of species native to the Red Sea to move through the Suez Canal and into the eastern Med, disrupting ecosystems, scientists say.

The threat is facing the entire Mediterranean, one of the fastest-warming seas, which this year saw its hottest June and July on record, figures from the Mercator Ocean International research centre show.

The striking but highly venomous lionfish (Pterois miles), for instance, with its long spotted fins that can measure around 26 centimetres, is now at home in such warm temperatures and wreaking havoc in the local ecosystem.

Invasive species are disrupting ecosystems across the eastern Mediterranean, the warmest area of the sea and the area that is heating up fastest. Many of these species are now moving further west.

In 2018, the Copernicus Marine Service noted the movements of an invasive fish species called silver-cheeked toad-fish pushing west across the Mediterranean. These fish have “highly opportunistic behaviour” and attack other fish captured in nets and lines, damaging the fishing industry.

The service warned that “without an intervention”, the species would continue its rapid spread.

Since then, water temperatures have continued to rise and more and more invasive fish species are being drawn further into the Mediterranean.

Last week, Mercator figures showed the sea had registered its warmest July on record with an average surface temperature of 26.68 degrees Celsius, a figure that is worrying experts.

This “tropicalisation” could also occur in the coming years through the Strait of Gibraltar at the west end of the Mediterranean basin, according to a study published in the prestigious US science journal PNAS (Proceedings of the National Academy of Sciences) in April 2024.

In it, the authors warned that even in an intermediate climate scenario, the warming of the Atlantic Ocean could see certain species migrate from the southern coasts of west Africa to the western Mediterranean by 2050.

A more pessimistic scenario could even see the Mediterranean “entirely tropicalised” by 2100, they warned.

Tropicalisation could also occur in the coming years through the Strait of Gibraltar at the west end of the Mediterranean basin, the narrow passage between southern Europe and northern Africa. Alamy Stock Photo Alamy Stock Photo

Murat Draman, a scuba diving instructor, is experiencing firsthand the rapid “tropicalisation” of the Mediterranean Sea.  

Recalling a recent dive, he said: “We were at a depth of 30 metres and the water was 29 degrees.”

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He said he has seen dozens of Red Sea species colonising the clear waters of Antalya off Turkey, where surface temperatures reached nearly 32 degrees this week.

“About a decade ago, we saw one or two of them. Now we’re talking about 15 or 20 per dive,” Draman said.

“They are big predators. Small fish like gobies suffer a lot, we hardly see them anymore.

Faced with such a threat, Draman said invasive species must be kept as far as possible from protected marine areas “in order to preserve biodiversity”.

“It is clear that with the absence of Mediterranean predators, species such as lionfish are very comfortable here and their population is increasing year on year,” he said.

“In the Red Sea, lionfish have predators. There are sharks and barracudas. Here, we have none of that.”

© AFP 2025