Application of time-lapse cameras to explore predation on reintroduction of endangered white abalone ( <i>Haliotis sorenseni</i> )

Climate instability, habitat modification, and serial depletion have precipitated population reductions to ecological and commercially significant species, with burgeoning reintroduction programs aimed at avoiding species level extinction. White abalone ( Haliotis sorenseni ) are a marine invertebrate that have experienced population reductions necessitating listing under the Endangered Species Act and subsequent intervention via reintroductions. Whether reintroductions are subject to immediate, overwhelming predation remains a critical component to the efficacy of species management regimes, yet marine environments can hinder direct observation. To bolster data on the influence of predator dynamics on H . sorenseni reintroductions, this study deployed time-lapse camera (TLC) arrays. Reintroductions occurred at two geographically distinct sites in southern California utilizing two outplant methods and spanning four stocking events from 2019 to 2022, reintroducing over 8000 H . sorenseni . Data (187,288 images) from 32 TLC deployments were analyzed to examine predator behavior, seasonal and diel variations, and effects on abalone mortality. Encounter rates of all predators were low and were not significantly affected by outplant module type. Rather than an immediate response to novel prey items, encounter rates varied by species. Lobster ( Panulirus interruptus ) and abalone were both nocturnal, creating higher risk of predation. However, lobsters were less commonly encountered following their fishing season, and were negatively affected by presence of urchins. Our results highlight the complexity of predation risks and suggest that small, targeted, site-specific adjustments, such as shifting outplanting to follow the fishing season of a predator or placing modules around urchins, may mitigate predation risk without necessitating large-scale changes.