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Staghorn Corals and Fish: Better Together

We know that organisms in an ecosystem are tied together in a delicate balance. We set out to find whether this was true for staghorn coral and fish that live on them. We wanted to know if they have a mutually beneficial relationship—if they help each other grow and survive.

Staghorn coral, which are listed as threatened under the Endangered Species Act, are essential fish habitat for spiny lobster, queen conch, and reef fish. Our research will help us plan how to help their struggling populations recover.

We looked at reefs in the U.S. Virgin Islands, Puerto Rico, and southeast Florida. We found the most robust staghorn populations in the Dry Tortugas (near Key West). They had extremely high densities of staghorn coral—up to twice as much as the other areas surveyed. These dense populations also had more fish, and a higher diversity of fish species.

But why? Do the abundant corals attract more fish, or do all the fish help the corals grow? We learned that, in the Dry Tortugas, fish help staghorn corals by providing them with extra nutrients when they excrete. The algae living within the coral use those nutrients to create energy, and help the corals grow.

We’ll use this information to help guide where we plant the staghorn corals we grow in nurseries. Rather than taking the “peanut butter” approach of spreading them thinly over a wide area, we could plant them in dense bunches. This could help us restore reefs that have a better chance of surviving, and provide healthy habitat for fish that live on the reefs.

Posted June 8, 2015

A sparsely populated coral reef in St. Thomas with few fish.
A reef in the Dry Tortugas with dense bunches of staghorn coral is teeming with fish.