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A wide range of ecological and environmental factors influence metal bioaccumulation in fish. Studies of mercury and other metal contaminants in invasive Indo-Pacific lionfish are limited, yet consumption of the invasive predator is increasingly utilized as a management strategy. In this study, we examined the effects of body size, body condition, sex, trophic level, carbon source, diet, depth and capture location on mercury concentrations in lionfish collected from Curaçao. In addition, we examined whether or not a local petroleum refinery is the source of metal contamination in lionfish. Mercury concentrations ranged from 0.008 to 0.106 mg/kg and we found no effect of the petroleum refinery on metal bioaccumulation in lionfish. Low concentrations of metal contaminants indicate lionfish from Curaçao are safe for human consumption.

Diet choice in marine species is typically derived from indirect methods such as stomach contents and stable isotope analysis, while choice experiments in controlled laboratory settings are used to infer foraging decisions in the wild. However, these methods are limited in their capacity to make inferences about foraging decisions by predators in variable environments or recreate the array of factors (such as prey traits, predator condition, and environmental conditions) present in natural systems which may interact to affect diet decisions by predators. Recent work has provided evidence for selectivity in the invasive Indo-Pacific lionfish (Pterois volitans/miles) despite the predator's apparent opportunistic, generalist feeding behavior. We directly tested diet choice by presenting wild-caught lionfish with multi-species prey assemblages in field enclosures. We offered lionfish equal biomasses of prey species sharing similar prey traits that are both highly abundant on coral reefs and prevalent in the lionfish diet across the invaded range. We then applied compositional analyses to determine relative prey consumption given prey availability. We observed lionfish selectively foraging on prey and manifesting strong consistent preferences for one prey species. Additionally, we observed condition-dependent foraging behavior, as lionfish with higher body conditions were more likely to exhibit selective foraging behavior. Our findings provide direct evidence for diet choice in an invasive generalist species and highlight the importance of preserving the ecological complexity of natural ecosystems in choice experiments, particularly when investigating predator-prey interactions in complex environments.