5 - Predation: piscivory and the ecology of coral reef fishes

Summary

Coral reef fishes are typically subjected to intense predation, especially by mid-trophic-level piscivores (mesopredators) targeting new recruits. Reef fishes thus display a broad variety of morphologies and behaviors associated with both capture and evasion. Different predators can interact with each other while foraging, cooperatively or negatively, and different prey species can interact in ways that increase or decrease the risk of predation. Short-term predator responses to changes in prey density, including functional and aggregative responses, have been quantified in only a few cases. Nonetheless, predation has often been found to be a source of direct density-dependent mortality in reef fishes, which in several studies has been further shown to regulate local populations. Such density dependence may involve interactions among different species of predator (synergistic predation), as well as predators forcing prey to compete for spatial refuges in the reef structure. In affecting the relative abundance of prey species, piscivores also structure reef fish communities. Differential colonization of reefs by predators affects subsequent relative recruitment rates of prey species (priority effects). Intense predation can extirpate relatively rare prey species via either differential consumption of those species or non-selective consumption. Coral reef fishes also provide examples of multiple piscivores consuming the same prey as well as each other (intraguild predation) and changes in the abundance of top predators, typically caused by overfishing, affecting abundance at lower trophic levels via mesopredator release (trophic cascades). Additional studies are needed to clarify the mechanistic local-scale patterns of predator–prey interactions in terms of both lethal and nonlethal ecological effects, as well as the broader holistic scale of predator–prey metapopulation and metacommunity dynamics, especially in the context of continued overfishing and reef degradation.

“Life feeds on life.”

Joseph Campbell

Two imperatives in the lives of animals are to eat and avoid being eaten. Thus, predation is often considered to be the primary ecological interaction among animal species [e.g. 533].