(Press release / 08-03-10) Researchers of the “Centro Oceanográfico de Baleares” of the IEO have found significant changes in the composition of the fish fauna of the Mediterranean Sea due to the increase of water temperature during the second half of the twentieth century.

38 new species have been located, most of them are exotic, coming especially from the Atlantic Ocean but also from the Indian Ocean. Besides, it was found that native species of the Mediterranean have suffered changes in their populations: while thermophilic species such as amberjack increase in the Balearic Sea, boreal species such as goby are in clear regression.

Data presented by researchers of the “Centro Oceanográfico de Baleares” of the IEO Enric Massutí, María Valls and Francesc Ordines in the chapter titled “Changes in the western Mediterranean ichthyofauna: signs of tropicalization and meridianization” of the book “Fish Invasions of the Mediterranean Sea: Change and Renewal” suggest that in the western Mediterranean, where there has been a rise in water temperature during the second half of the twentieth century, global warming has influenced the composition of fish populations.

During this period, the presence of 38 new species in the western Mediterranean has been documented. Almost all of them are exotic species from tropical and subtropical Atlantic, which came across the Gibraltar Strait. This phenomenon, known as “tropicalisation”, is changing the identity of the Mediterranean.

It is difficult to know if any of these new species has formed stable populations, although it seems that they are expanding their presence to the north and east of the Mediterranean, reaching the eastern basin.

It was also observed a movement of exotic species to the opposite direction. Thus, some species with Indo-Pacific origin, arrived via the Suez Canal, have expanded their distribution to the west, even crossing the Sicilia Canal.