Evaluating the effects of marine reserves on diet, prey availability and prey selection by juvenile predatory fishes

Abstract

ABSTRACT: Implementation of effective no-take marine reserves almost universally results in anincrease in the abundance of adult stages of exploited predatory fishes. However, the effects ofreserves on the ecology of the juvenile stages of predators are unknown. Increased predationpressure from adults in reserves may not only reduce juvenile recruitment directly, but as a resultof non-consumptive effects, may impact on critical aspects of their foraging behaviour, includingdiet and prey selection. In general, the feeding ecology of juvenile stages of large predators ispoorly understood due to their relatively low abundance and cryptic behaviour. Here, we exam-ined differences between reserves and fished areas in recruit abundance, diet, prey availability,and prey selection indices for recruits and juveniles of 3 predatory fishes: Plectropomus macula-tus , Lutjanus carponotatus and Epinephelus quoyanus . Recruit abundance was similar betweenreserves and open areas. The diets of the 3 study species did not differ between reserves and openareas, with variation in diets largely explained by fish species and body size. At small sizes, allspecies consumed high numbers of shrimp, but diets diverged with growth. Overall, our resultsprovide little evidence that more abundant predators inside reserves influence juvenile feedingecology.KEY WORDS: Coral reef · Predator–prey relationships · Non-consumptive effect · Marinereserves · Serranidae · Lutjanidae · Great Barrier Reef · Recruitment