Density manipulation of the Caribbean King Crab facilitates community-level recovery of coral reef systems in the Florida Keys
Jason Spadaro and Mark Butler
The well-documented declines in both live coral cover and herbivore abundance throughout the Caribbean and Florida Keys has resulted in the degradation of the region’s coral reef communities and the proliferation of fleshy benthic macroalgae. Most restoration efforts have focused on either directly enhancing live coral cover via transplantation of nursery-reared corals, the protection of herbivorous fishes (e.g., parrotfishes), or the re-introduction of herbivorous urchins (i.e., Diadema) lost after epizootics. Unfortunately, Diadema populations have failed to recover more than 30 years after the regional pandemic, save for a few areas in the Caribbean. Similarly, legislative efforts to protect parrotfish have been only marginally successful. Yet, another potential avenue for restoring degraded coral reefs may exist via enhancement of existing populations of the Caribbean King Crab (Maguimithrax spinosissimus, formerly Mithrax spinosissimus). Maguimithrax is a cryptic, large-bodied crustacean herbivore whose natural low abundance on coral reefs, due to high predation on juveniles, minimizes their effectiveness as a reef herbivore. However, when their density is increased through stock enhancement, their effect on coral reef community structure is remarkable. When we manipulated crab density on shallow nearshore patch reefs and monitored their effect for 1-2 years we found that crabs reduced algal cover~80%, resulting in a three-fold increase in coral recruitment, and significant increases in both the abundance and diversity of benthic and demersal reef fishes relative to control reefs. We have replicated these experiments in two locations within the Florida Keys National Marine Sanctuary and are confident that this remarkable species bears further scrutiny as a candidate for coral reef restoration initiatives throughout the region.
Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529 [email protected]
Jason Spadaro and Mark Butler
The well-documented declines in both live coral cover and herbivore abundance throughout the Caribbean and Florida Keys has resulted in the degradation of the region’s coral reef communities and the proliferation of fleshy benthic macroalgae. Most restoration efforts have focused on either directly enhancing live coral cover via transplantation of nursery-reared corals, the protection of herbivorous fishes (e.g., parrotfishes), or the re-introduction of herbivorous urchins (i.e., Diadema) lost after epizootics. Unfortunately, Diadema populations have failed to recover more than 30 years after the regional pandemic, save for a few areas in the Caribbean. Similarly, legislative efforts to protect parrotfish have been only marginally successful. Yet, another potential avenue for restoring degraded coral reefs may exist via enhancement of existing populations of the Caribbean King Crab (Maguimithrax spinosissimus, formerly Mithrax spinosissimus). Maguimithrax is a cryptic, large-bodied crustacean herbivore whose natural low abundance on coral reefs, due to high predation on juveniles, minimizes their effectiveness as a reef herbivore. However, when their density is increased through stock enhancement, their effect on coral reef community structure is remarkable. When we manipulated crab density on shallow nearshore patch reefs and monitored their effect for 1-2 years we found that crabs reduced algal cover~80%, resulting in a three-fold increase in coral recruitment, and significant increases in both the abundance and diversity of benthic and demersal reef fishes relative to control reefs. We have replicated these experiments in two locations within the Florida Keys National Marine Sanctuary and are confident that this remarkable species bears further scrutiny as a candidate for coral reef restoration initiatives throughout the region.
Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529 [email protected]