Threespot damselfish use algae crops for building nests and feeding; these activities are killing corals in the Caribbean. Scientists used to believe that overfishing of threespot damselfish predators allowed the damselfish to gain numbers and kill more coral, but overpopulation isn’t the reason.
Coral reef ecologist Rich Aronson from the Florida Institute of Technology says, “Our surveys of reefs around the Caribbean show that the number of predatory fishes is not the key to how damselfish live on a reef. It’s all about real estate — places to live.”
The reason why threespot damselfish are killing more corals than before is actually because of the decline of staghorn corals. Until the 1980s, these fish had gardens in staghorn corals, which at the time was the most abundant coral in the Caribbean. Staghorns grew fast and could cope with damselfish nipping at them while eating algae. Coral disease outbreaks and other environmental causes decimated the staghorn coral population so much that it is now listed as “threatened” under the U.S. Endangered Species Act..
After the decline of staghorns, the damsels had to switch to farming on other corals — slower-growing corals that would take longer to recover from damsel damage. Scientists believe that restoration of staghorn corals is the key to fixing the damage.