The Mediterranean is the ''most invaded'' sea on earth, Italy's marine environment protection agency IRPA said Thurday.
Two alien species now enter the Med each month, IRPA said, with fish leading the way.
Whether imported for fish farms or simply swimming in from the Atlantic and up the Suez Canal, fish have been arriving at increasing rates in recent years, IRPA research director Franco Andaloro said.
Red Sea fish have been favoured by a change in currents while tropical fish have also been coming in from the western ocean whose stock has changed because of global warming, he said.
Foreign visitors have shown a 20% rise in the last four years, 30% in Italian waters alone.
And the Med is struggling to cope with the assault.
''The sea has been weakened by environmental stress and over-fishing,'' Andaloro said.
Barracudas, parrot fish and trigger fish have ''surged'', knocking the food chain out of whack and threatening ecosystems, said the IRPA chief.
But alien species are for the moment steering clear of marine reserves where native fish are holding out, Andaloro said.
