Abstract

To gain insight about how an invasive predator influences native prey, we performed a series of controlled experiments in aquaria to characterize and compare the prey preferences of the invasive red lionfish (Pterois volitans) and an ecologically-similar native mesopredator, the graysby grouper (Cephalopholis cruentata). Preference for native congeneric fishes, the fairy and blackcap basslets (Gramma loreto and G. melacara, respectively) were tested. We observed behavior of predators in response to two individual prey consisting of cross-factored combinations of species (fairy and blackcap basslets) and size (small and large). Upon initial exposure to prey, lionfish first hunted fairy basslet and graysby hunted blackcap basslet first, and both predators initially preferred large over small fish. Overall predatory behavior quantified from the entire duration of observation indicated both predators lacked a preference between basslet species based on total number of strikes and hunting time. Despite essentially identical size ranges of predators studied, graysby overall preferred large basslet across all graysby sizes, whereas the overall preference of lionfish between prey size varied with lionfish size. Importantly, the initial preferences of predators were least affected by the unnatural setting in aquaria and thus more likely reflected true predatory behavior. This study demonstrates aspects of prey preference that are either different or similar between invasive and native predators. The combination of these predators could at one extreme enhance coexistence within and between basslets, or at the other extreme, deplete local basslet populations via increased overall predation.

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