Tropical fish are heading north

POLLUTION AND global warming are helping to turn the Mediterranean into a tropical aquarium, with native fish species being threatened with extinction by up to 110 newcomer varieties, experts warned yesterday.

The interlopers are threatening to crowd out native species less suited to the ever-warmer and more polluted waters, said Italy's Central Institute for Scientific Research and Applied Technology for the Sea. It said the Mediterranean's first species of tropical fish arrived in the Thirties, three decades after the opening of the Suez Canal. Since then, 55 Red Sea species have made their way in via the canal.

The new research was presented to the Environment Minister, Edo Ronchi, yesterday. "The tropical fish, having evolved in conditions of rapid natural change in highly competitive environments like the Red Sea, can easily spread in the Mediterranean," said Franco Andaloro, author of the study.

"The competition with Mediterranean species in terms of habitat selection, the search for food and reproductive success could lead, in extreme conditions, to the extinction of the weaker species."

Scores of other tropical species have entered through the Straits of Gibraltar, and the overall level of fish in the Mediterranean has increased by 20 per cent because of the influx. In comparison with a native population weakened by pollution and over-fishing, the newcomers are thriving among the 530 indigenous species.

The study warned that the whole ecology is being altered by the reordering of the food chain: "The most disturbing aspect of this phenomenon consists of the impact on the ecosystem in the western and central Mediterranean."