Abstract

Invasive species exert profound impacts on the systems to which they are introduced. Understanding the threat posed by an invasive species is undoubtedly the first step to mitigating its impact. However, these impacts are often difficult to both forecast and quantify (Lockwood et al. 2013). Quantifying the impacts of marine invasive species is especially critical, whose study has historically lagged behind their freshwater and terrestrial counterparts (Tricarico et al. 2016). Functional response is a novel way with which to predict and quantify the impact of invasive species by comparing their feeding rates and thus their per capita impact on prey populations, relative to the native analogues with which they occur (Dick et al. 2014). Unfortunately, most experiments of this vein lack habitat heterogeneity, limiting their applicability and transferabil-ity (Jeschke et al. 2002). Lionfish are one such marine invasive species whose impacts have drawn substantial attention from researchers. However, we continue to lack a thorough understanding of their feeding and behavioural ecology across their invaded range and relative to ecologically similar native predators with which they co-occur. Therefore, we sought to better understand the impacts of lionfish in an understudied region of its invaded range, the eastern Gulf of Mexico. We conducted comparative, feeding rate laboratory experiments with each of three species across six prey densities. Pink shrimp (Penaeus duorarum) sufficed as prey. Trials were conducted in a circular experimental tank, comprised of three patches of equal area but distinct habitat. Prey was replaced as they were consumed throughout the three-hour trial duration. Lionfish per capita impact was contrasted against two native species, red (Epinephelus morio) and graysby (Cephalopholis cruentata) grouper.

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