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Overfishing causes an increase in "coral ticks" that damage coral reefs



A small, overlooked snail could contribute to the sinking of coral reefs.

Scientists at the Georgia Institute of Technology have investigated how the Coralliophila violacea snail could further weaken already damaged reefs. The study published in Ecological Applications on Thursday found that the snail could reduce the growth of an important coral species Porites cylindrica . The Porites coral can form a basis for reefs as it is less susceptible to seaweed and other threats.

"The Porites Coral is a kind of last man, the last hope for some of these reefs coming back They are the ones who selectively hunt these snails," said Mark Hay, professor at Georgia Tech and author on paper, in a statement, "As you get fewer and fewer corals, the snails concentrate on the fewer and fewer of these colonies." This is part of the downward spiral of the reefs. "

The coral reefs are already weakened by pollution, rising sea temperatures, invasive species, and other factors , This snail, which is about half an inch in length and almost 2 centimeters long, sucks liquid from the coral, which is why they are called "coral ticks".

The scientists found a clear link between the number of fish in an area and the number of corals in Fiji's Coral Coast. On a single colony in areas where fishing is prohibited, Cody Clements, an author on paper, never found more than five snails. In areas where fishing is allowed, he found 35 times more snails on the coral.

Overfishing affects coral reefs, as fish are known to control marine algae and predators. To see how the larger amounts of snails affected the corals, Clements attached snails to isolated coral branches. He compared these branches after 24 days with twigs without snails. Depending on the size of the snails, coral growth decreased by 1

8 to 43 percent.  Tortoise and coral reef Tourists snorkel near a turtle as she searches for food among the coral in the lagoon at Lady Elliot Island northeast of the city of Bundaberg in Queensland, Australia. The coral reefs are weakened by pollution, rising sea temperatures, invasive species and other factors. DAVID GRAY / REUTERS

Clements, who removed more than 2,000 snails with a pair of pointed pliers while confirming his research, that the lack of fish causes an increase of snails by tethering snails on reefs in areas that allow fishing and those who do not. The snails in the areas that do not permit fishing were eaten, probably by triggerfish and other fish with teeth, while those in areas that allow fishing were not eaten. In areas protected from fishing, 220 per cent more snails were hunted than in areas that allow fishing.

"A single snail can do a considerable amount of damage," Clements said in a statement. "They suck the juice out of the coral, and if you have a lot of snails feeding on a single coral colony, it can be very difficult for the colony to thrive."


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