Modeling fish biomass structure at near pristine coral reefs and degradation by fishing and global warming

Background/Question/Methods   Until recently, the only examples of inverted biomass pyramids have been in freshwater and marine planktonic communities. Investigators have documented inverted biomass pyramids for nearly pristine coral reef ecosystems within the NW Hawaiian islands and the Line Islands, where apex predator abundance comprises up to 85% of the fish biomass. We construct a refuge based model to study the fish biomass structure at coral reefs. Our mechanistic model contains a refuge of explicit size to account for the coral holes that hide much of the prey from the predators.

Results/Conclusions   Utilizing realistic life history parameters of coral reef fish, our model exhibits a stable inverted biomass pyramid. Our model also exhibits the increasing dependence of biomass ratio on refuge size, which was found in the field studies. We use our model to show that fishing transforms the inverted biomass pyramid to be bottom heavy, and we investigate consequences of environmental shocks and global warming on a nearly pristine coral reef.