High predatory efficiency and abundance drive expected ecological impacts of a marine invasive fish

Abstract

The ecological impacts of invasive species are highly variable and mediated by many factors, including both habitat and population abundance. Lionfish Pterois volitans are an invasive marine species which have high reported detrimental effects on prey populations, but whose effects relative to native predators are currently unknown for the recently colonized eastern Gulf of Mexico. We used functional response (FR) methodology to assess the ecological impact of lionfish relative to 2 functionally similar native species (red grouper Epinephelus morio and graysby grouper Cephalopholis cruentata) foraging in a heterogeneous environment. We then combined the per capita impact of each species with their field abundance to obtain a Relative Impact Potential (RIP). RIP assesses the broader ecological impact of invasive relative to native predators, the magnitude of which predicts community-level negative effects of invasive species. Lionfish FR and overall consumption rate was intermediate to that of red grouper (higher) and graysby grouper (lower). However, lionfish had the highest capture efficiency of all species, which was invariant of habitat. Much higher field abundance of lionfish resulted in high RIPs relative to both grouper species, demonstrating that the ecological impact of lionfish in this region will be driven mainly by high abundance and high predator efficiency rather than per capita effect. Our comparative study is the first empirical assessment of lionfish per capita impact and RIP in this region and is one of few such studies to quantify the FR of a marine predator.

Predatory ability and abundance forecast the ecological impacts of two aquatic invasive species

“…Here, we examined per capita effects of two notorious invasive species using functional response (FR) methodology and the new Functional Response Ratio (FRR) and, subsequently, examined how these effects were modified by each species' abundance using the Relative Impact Potential (RIP). This combined experimental approach links per capita feeding rate with field abundance to provide best estimates of invader impact relative to comparable native species (Dick et al 2017a;DeRoy et al 2020).…”

“…Dick et al (2017a) thus devised a new metric, the Relative Impact Potential (RIP), that incorporates per capita feeding rates and local field abundances as proxies for functional and numerical responses, respectively, to predict the ecological impact of an invasive species versus that of a comparative native species. This method shows promise to screen potential invasive species and perform rapid impact assessments of established (as well as potential) invaders on both prey communities and relative to co-occurring native predators (Hoxha et al 2018;DeRoy et al 2020;Dickey et al 2020a). Indeed, the RIP metric was 100% successful in its ability to predict the actual field impacts of a range of invasives across trophic and taxonomic groups (Dick et al 2017a).…”

Invasive lionfish detected in estuaries in the northern Gulf of Mexico using environmental DNA

“…Lionfish are generalist predators with broad temperature and salinity tolerances (Jud et al 2015;Barker et al 2018;Peake et al 2018;Rojas-Vélez et al 2019). As highly successful and indiscriminate predators in their invasive range (Albins and Hixon 2008;Morris and Akins 2009;Barbour et al 2010;Kindinger and Albins 2017;Peake et al 2018), lionfish have become dominant predators (DeRoy et al 2020). The combination Abstract Invasive lionfish are considered to be one of the worst marine invaders primarily due to their threat as predators to native species.…”

“…In this study, an environmental DNA assay was developed and successfully identified the presence of lionfish DNA in four riverine estuaries in the northern Gulf of Mexico. Detections were of high abundance and predator efficiency causes a greater impact on food webs than that of natural predators (DeRoy et al 2020). On reef systems, invasive lionfish are capable of decreasing recruitment of fish by 80% (Albins and Hixon 2008).…”

“…For instance, in Lake Erie, predation by a native fish, Burbot (Lota lot), on invasive Round Goby (Neogobius melanostomus) has reduced the invasive population (Madenjian et al 2011). Current knowledge of impacts of invasive lionfish on food web dynamics suggests native predators will not be sufficient (Albins and Hixon 2008) (DeRoy et al 2020). Other methods of biological control, such as genetic techniques or the use of viruses, may be highly effective, but require careful consideration due to potential unintended consequences (Bajer et al 2019).…”