Many healthy reefs dominated by corals have transitioned to degraded reefs dominated by seaweeds. Impact of this phase shift on the behavior and survivorship of coral reef fishes is poorly understood, but could affect survival of recruits and export of juveniles from healthy to degraded locations where fishes could enhance reef resilience and recovery. Using experimental patch reefs in pairs of adjacent healthy (MPAs) and degraded (non-MPAs) reefs, we identified between-habitat differences in predators, patterns of attack, and prey behaviors that affect survival in these divergent habitats.
Primary predators in MPAs were rapidly moving wrasses attacking from above; prey here selectively used higher portions of the reefs where they could visually monitor predators. Conversely, predators in seaweed dominated, non-MPAs were sit-and-wait lizardfish, sand perch, and cod ambushed upward from the benthos. Prey here selectively used lower portions of reefs where they could presumably better detect chemical cues from sit-and-wait predators. In both situations, prey seemed selected to detect, rather than spatially avoid, predators. Prey fishes reciprocally moved from MPA to non-MPA, or vice versa, experienced a 3-16 fold increase in mortality compared to fishes relocated within their initial habitat. Prey that survived relocation adjusted behaviors to match fishes naturally found within the new habitat. Here we show that even very plastic behavioral traits could limit movement or “spillover” from healthy to degraded sites because fishes moving between habitats will initially display behaviors that lower their survivorship in adjacent habitats with differing conditions, consumers, and threats. Our findings suggest that habitat quality, predator community composition, and prey behaviors interact to affect prey survival, and that prey behavior is dynamic and crucial as reefs under-go regime shifts.