MEPS 574:85-95 (2017)  -  DOI: https://doi.org/10.3354/meps12187

ABSTRACT: Predation effects can occur either through consumption or as risk effects, which can include alterations in prey behavior to decrease encounters, detection and/or capture by predators. Perceived predation threats lead to behavioral responses which may manifest as changes in habitat use by the prey, and these effects can be significant and even greater in population-level consequences and across multiple trophic levels than consumptive effects. In Bimini, Bahamas, juvenile lemon sharks (Negaprion brevirostris, Poey 1868) use mangrove-fringed shorelines as nursery areas in part due to protection afforded from predators, namely, large conspecifics. We investigated small-scale use (on the order of meters) of artificial mangrove structure by juvenile N. brevirostris as an antipredatory response to perceived predation risk. Controlled experimental trials were conducted on semi-captive individuals to compare the degree to which sharks used artificial subtidal refugia when solitary, with a size-matched conspecific and with a potential predator (large conspecific). Test shark size and predator presence were significant drivers of artificial mangrove use. There was a negative relationship between body size and refuge use in the presence of a predator, indicating that size is an important factor influencing antipredatory behavior. Test sharks exhibited a high degree of social swimming behaviors with size-matched conspecifics, but the presence of a large conspecific predator elicited fright reponses. This study provides the first experimental evidence of the influence of intraspecific predator-prey interactions on juvenile shark habitat use and demonstrates use of subtidal structure as a habitat-specific escape tactic.

KEY WORDS: Risk effects · Risk of predation · Habitat loss · Mangroves · Predator-prey interactions · Refuge