Predators and habitat association of post-settlement snapper (Chrysophrys auratus).

Structured habitats play an important nursery role during the crucial early juvenile or post-settlement stages of many fish species. Predominantly, the utility of structured habitats to juvenile fish is thought to be associated with the provisioning of food or as a refuge from predation. Although snapper (Chrysophrys auratus) in New Zealand also have a strong affinity for structured habitats during their post-settlement phase, their predators are unknown as is the role of predation in determining habitat association. Here the authors investigated potential predators of post-settlement snapper by remotely observing interactions of restrained post-settlement snapper with potential predators and investigating the diet of potential predators. They also conducted tank experiments with a potential predator, both with and without the presence of structure. Restrained snapper were infrequently approached by predators, but two new nocturnal predators were identified. No snapper were observed in the diet of potential predators, although two piscivores were identified as potential candidates. No predation occurred during tank experiments, but there was a non-significant indication that under threat of predation post-settlement snapper may use habitat when it is present and aggregate together when it is not. The findings suggest that the pulsed nature of predation may have made it difficult to observe given the methods employed and that the threat of predation may be sufficient to drive the habitat selection of post-settlement snapper. Investigating the significance of predation via methods that do not require direct observations may therefore be more appropriate given this context.