Two species of tropical fish that have made their way through the Suez Canal to the eastern Mediterranean are devastating the ecosystem there, according to a new study that says these fish pose a threat to the entire Mediterranean basin.
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The study, by an international team of researchers led by Adriana Vergés of the University of New South Wales in Australia and Fiona Tomas of the Mediterranean Institute for Advanced Studies in Spain, was published recently in the Journal of Ecology.
The study authors note that the findings in the Mediterranean reflect a world trend, and there are now 80 species of tropical fish threatening marine plant life all over the world. If the climate changes persist and sea temperatures continue to rise, these fish will have an increasing ecological impact, the researchers add.
Members of the team surveyed more than 1,000 kilometers of coastline in Turkey and Greece, where two species of the tropical rabbitfish have become dominant since they moved into the region via the Suez Canal. These fish are also found off the Israeli coast, and are referred to as arras by local fishermen.
According to Daniel Golani of the Hebrew University of Jerusalem, these are vegetarian fish, and because most of the species in the Mediterranean are not, the rabbitfish do not have much competition for resources.
The researchers tracked the fish through dives and video footage in different areas of the sea. They also collected samples of flora and fauna, and examined the coverage of sea grass and algae on the bedrock on the sea floor.
These rabbitfish are more common in the warmer areas of the Mediterranean than in the colder regions. In those areas where there was a higher population of rabbitfish, the researchers said, there was a 65 percent reduction in large seaweed, a 60 percent reduction in other algae and invertebrates, and a 40 percent reduction in the overall number of species present. According to the researchers, areas of the Mediterranean where these fish are found have been turned into an ecological wasteland.
The researchers compared the activity of vegetarian fish that are native to the Mediterranean, and found that while the native fish actually eat larger amounts of vegetation than the rabbitfish, they only eat adult algae, while tropical fish also eat young algae. This prevents algae forests from developing.
The extensive damage to the flora also affects the animals that depend on it for food.