The role of fishes as food: A functional perspective on predator-prey interactions

Abstract

<p>1. Every animal dies. In nature, mortality usually occurs due to predation by other animals. One of the fundamental consequences of mortality is the transfer of energy and nutrients from one organism (prey) to another (predator). On coral reefs, these key interactions and processes, that are essential for ecosystem functioning, are primarily mediated by fishes; up to 53% of fishes on coral reefs can be regarded as piscivorous.</p><p> 2. To date, piscivory on coral reefs has been primarily studied with regard to the species piscivores feed on, and how piscivores control populations. Consequently, understanding prey selectivity by piscivorous fishes has been a major goal. However, prey functional traits may also be important in understanding these ‘energy transactions’, especially in complex ecosystems such as coral reefs.</p><p> 3. Our goal, therefore, was to quantify-at a community level-functional traits of prey that have been shown to influence predator-prey interactions. We found that, on average, deep‐bodied, social fishes occupy higher positions in the water column, whereas solitary species are usually elongate and more closely associated with the benthos. On closer examination, we found that solitary species have a size‐dependent relationship, with substratum associations shifting to water column associations, at approximately 50 mm body length.</p><p> 4. Our results reveal three distinct prey functional groups: cryptobenthic substratum dwellers, solitary epibenthics and social fishes. These groups display significant differences in their morphologies and behaviours. Furthermore, based on a meta‐analysis of published mortality rates of small‐bodied (<100 mm TL) reef fishes, we show that the three groups display different mortality rates, possibly due to differential exposure to, and potential to be captured by, different predator types.</p><p> 5. Although fishes are widely available on coral reefs, they may not be equally available as prey to all piscivore types. Prey are not simply victims; they are capable of influencing potential predation through functional traits.</p>