By studying heavily fished areas where fish trapping is common and comparing them to more protected areas, Dr. Loh has shown a link between the overfishing for angelfish and parrotfish and smothering of coral by sponges. Because parrotfish and angelfish are natural predators of fast-growing sponges, shrinking populations of these fish in some areas is causing coral to be killed off by the out-of-control sponges.
While threats to coral are already a deep ecological concern, as it has been recently reported, the coral reef ecosystem represents a $30 billion boost to the global tourism economy, and the loss of reefs and other ecosystems could cause world oceans to lose an estimated $1 trillion in economic value by the end of the century. 
“If the goal is to save the corals that build the Caribbean reefs, we have to protect the angelfishes and parrotfishes that eat sponges,” Dr. Loh said.
In order to complete the study — which was released today in open access journal PeerJ — nearly 70 sites in 12 countries in the Caribbean were surveyed. Twenty-five percent of coral colonies were in contact with sponges at sites with lower fish populations because of overfishing, more than double the incidence than in areas with less fished reefs.
Yellow tube sponge Aplysina fistularis smothering the reef coral Siderastrea sp. 
Both Dr. Loh and Dr. Pawlik hope that their research can help guide the fishing policies of Caribbean nations.
“Caribbean nations can now base their fishing policy decisions on the clear connection between overfishing and sponge-smothered corals,” Dr. Pawlik said. “Coral conservation requires a healthy population of reef fishes.”
Aside from her research into coral and sponges, much of Dr. Loh’s work is based in Thailand, Vietnam and Indonesia, setting up long term study sites on seahorse populations alongside longtime Shedd partner Project Seahorse.
By: voices.nationalgeographic.com
