Temporal and spatial patterns in behavioral responses of marine predators to a sudden influx of abalone prey (Haliotis rufescens)

Abstract

Predator–prey interactions exist on a variety of spatial and temporal scales; one of the earliest measurable responses to changes in these interactions is behavior. We examined the behavior of southern California kelp forest predators in response to a concentrated increase in the abundance of abalone during a restoration stocking experiment. We tested three hypotheses: (1) kelp forest predator density will increase following abalone stocking, (2) variations in predator characteristics will create an unequal impact on abalone, and (3) predation intensity will be greatest early in the experiment. Octopus discovered and exploited the influx of prey within the first week following stocking; their densities surged and then returned to pre-stocking levels after 2 months. This was not observed with any other predator. Damage from crustacean, fish, and octopus predation was observed on the recovered abalone shells, but were not correlated with predator densities. A larger percentage of recovered small shells had evidence of crustacean and fish predation, indicating there may be size-specific impacts of predators on abalone. Our results demonstrate that restoration stocking experiments can quantitatively test the predatory community’s response to reintroductions, as well as predation risk of newly stocked prey species when exposed to a diverse suite of predators.