Warming seas are extending the range of tropical rabbitfish, whose voracious appetite for marine vegetation is turning areas of the Mediterranean Sea into rocky barrens.
Scientists have identified a new menace in the Mediterranean: the tropical rabbitfish, which threatens to do to marine vegetation what the rabbit did to Australia’s grasses: eat the lot.
The invaders are a threat to ecosystems because seaweed forests − like terrestrial forests − provide food and shelter for hundreds of species. Wiping out seaweed could be a threat not just to Mediterranean ecosystems but also to the Mediterranean diet because these ecosystems ultimately support of sardines, anchovies, sea bass, tuna and other specialties of the tables of Spain, Greece and Italy.
A team of researchers led by Adriana Vergés, a marine ecologist at the University of New South Wales in Sydney and Fiona Tomas, assistant professor at the Mediterranean Institute for Advanced Studies in Spain, surveyed 1,000 kilometres of coastline around Turkey and Greece and found that two species of rabbitfish have become dominant in the region.
The northern advance of the rabbitfish, which first entered the Mediterranean from the Red Sea via the Suez Canal, provides a good example of how tropical, herbivorous fish can change and damage the structure of rocky bottoms in temperate seas.
“The study identified two clearly distinct areas − warmer regions with abundant rabbitfish, and colder regions where they are rare or absent,” Dr Vergés said. ”The regions with abundant rabbitfish had become rocky barrens. There was a 65% reduction in large seaweeds, a 60% reduction in other algae and invertebrates, and a 40% reduction in the overall number of species present.”
The hungry herbivores were first reported in the eastern Mediterranean in 1927, and have recently been found off the coast of Croatia and even the south of France.
The researchers found the rabbitfish were not noticeably more greedy than native fish. But whereas the native herbivores grazed only on adult algae, the rabbitfish consumed both adult and juvenile seaweeds, meaning that the algae will not be replenished.
“This research highlights the need to work out how the interactions between different species will change in a warming world,” Dr Vergés said. − Climate News Network