Caribbean king crab
A native grazer, back on the reef.
Belize's first attempt to raise Caribbean king crab on land and return it to reefs that have lost their herbivores. Pilot stage.
Why a crab
Corals need bare rock to settle on. On a lot of Caribbean reefs that space is taken by macroalgae, the tough seaweed that fish and urchins mostly leave alone. The Caribbean king crab (Maguimithrax spinosissimus) eats it. It is a native Belizean herbivore, and it eats more algae per gram of body weight than nearly all Caribbean parrotfishes.
This is a native species, so the work is restoring a depleted population, not introducing anything new.
The pilot
FINS is building a low-tech, land-based recirculating system at Independence Village to raise juvenile crabs through their vulnerable early stages and then place them on reefs that have lost their grazers. Our technical partner is Healthy Reefs for Healthy People, the only organisation with demonstrated experience producing this species in the Western Caribbean; they have placed roughly 200 juveniles on reefs in Mexico.
Where it stands: the water and biological media in the system are maturing. Broodstock is not yet established. Nothing has been placed on a reef yet. This is Belize's first attempt at it, and we'll report what happens either way.
The evidence behind it
In the Florida Keys, Spadaro and Butler (2021, Current Biology 31(4): 853 to 859) placed these crabs on 24 replicate patch reefs and recorded seaweed cover falling by 50 to 80 per cent and coral recruitment rising three to five fold. That is one study in one place. It is the reason to try, not a promise about what a small pilot in Belize will do.