Recent research carried out on reefs from the Bahamas to Belize suggests that as Caribbean damselfish lose their preferred coral habitat, they move on to, and damage, other kinds of coral.
Damselfish are killing head corals and adding stress to Caribbean coral reefs, which are already in desperately poor condition from global climate change, coral diseases, hurricanes, pollution, and overfishing. Restoring threatened staghorn coral, the damsels’ favorite homestead, will take the pressure off the other corals, according to a new study published in the online journal PLoS ONE.
“Our surveys of reefs around the Caribbean show that the number of predatory fish is not the key to how many damselfish live on a reef,” says [author Rich] Aronson. “It’s all about real estate—places to live.” Until the 1980s, threespot damselfish tended their gardens in staghorn coral, at the time the most common coral in the Caribbean. Staghorn coral, named for its long, thin branches, grew very fast and could keep ahead of the damselfish onslaught. The threespots preferred staghorn above all other corals for its tangle of branches, which provided ideal places to hide, feed, and nest. Although the threespots bit and killed portions of staghorn colonies, the living branches that remained continued to thrive. But outbreaks of coral diseases, compounded by hurricanes and other environmental insults decimated populations of staghorn coral to the point that it is now listed as threatened under the U.S. Endangered Species Act.
Coauthor Les Kaufman is a fish biologist with Boston University and Conservation International. He explains, “Once staghorn coral disappeared, the fierce little beasts switched to killing slow-growing coral heads.” Coral heads are a lot less desirable from the damsels’ point of view because they have fewer hiding places. Unlike staghorn coral, head-corals cannot recover quickly enough to keep pace with the death-bites of threespot damselfish, so the coral heads could take hundreds of years to recover.
[Photo: Kyle and Shannon Johnson]