Within its range, tomtate is abundant on most reefs south of Chesapeake Bay and serves as prey to many economically important species such as snappers and groupers 16. Tomtate is a small grunt species that schools on reefs in Atlantic waters from Cape Cod, Massachusetts, to Brazil 16, 17. The current study presents results on the abundance of tomtate ( Haemulon aurolineatum) from North Carolina to Florida over the entire course of the lionfish invasion (1990–2014). Thus, studies that quantify the regional-scale impact of the lionfish invasion over multiple years are sorely needed. Additionally, the study lacked a non-invaded control group. While one other study did investigate abundance changes in native reef fish in relation to lionfish, the study contained only 2 time points (20) and was also conducted in a localized area off of the Bahamas 15. Consequently, the impact of the ongoing lionfish invasion on native fish remains poorly understood. However, experimental manipulations of lionfish densities have focused on the effect of invasive lionfish near the upper bound of their natural densities (in their invaded range), have been short in duration (weeks to months) and have been conducted on relatively small spatial scales (5–30 km 2) in localized areas off of the Bahamas 10, 12, 14. The combination of results from lionfish density monitoring studies 8, 9 and experimental manipulations of lionfish densities 10, 12, 14 suggest that lionfish have been negatively affecting the abundance of native fish in Atlantic waters off of the SEUS since the early- to mid-2000s.
Further, modeling efforts have demonstrated that lionfish densities of roughly 250 ha −1 are sufficient to deplete prey fish populations faster than they can replenish themselves 14. Similar negative effects have also been documented at lionfish densities of 250 lionfish per hectare 14.
SMART UTILITY VOLITANS PATCH
When lionfish densities were controlled on larger experimental patch reefs (0.16–0.40 hectares) and over a longer time period (14 months), the abundance of prey fish at sites with 300 lionfish ha −1 was roughly 40% lower than the abundance of prey fish at sites with 30 lionfish ha −1 10. The introduction of a single lionfish into 4 m 2 experimental patch reefs reduced recruitment of native prey fish by an average of 79% over a 5-week period 12. Today, lionfish densities exceed those of all but the most common predatory fish species on many reefs in the Caribbean and off of the SEUS 10, 11.Įxperimental manipulations on patch reefs have demonstrated that lionfish can negatively affect native forage fish populations 12, 13. By 2008, the maximum lionfish densities observed off North Carolina were approximately 450 lionfish ha −1, with mean densities of about 150 lionfish per hectare 9. The first assessment of lionfish densities in their non-native range, which was conducted in 2004, reported an average of 21 lionfish ha −1 across 17 locations off North Carolina 8. Once introduced, their growth rate, high fecundity, generalist foraging habits and lack of predators led to their rapid spread 5, 6, 7. The lionfish invasion is thought to be the result of multiple lionfish release events that occurred via the aquarium trade during the late 1980s and early 1990s 3, 4. volitans), both collectively referred to as lionfish in this study, are generalist piscivores that have invaded Atlantic waters off of the southeastern United States (hereafter abbreviated as SEUS), the Gulf of Mexico and the Caribbean 1, 2. The devil firefish ( Pterois miles) and the red lionfish ( P. Consequently, the effect of lionfish on native fish abundance will likely continue for the foreseeable future. Barring the development of a control strategy that reverses the lionfish invasion, the abundance of lionfish in the Atlantic, Caribbean and Gulf of Mexico will likely remain at or above current levels. Tomtate served as a model native fish species in our analysis and as such, it is likely that the lionfish invasion has had similar impacts on other species, some of which may be of economic importance. Our results suggest that 1) lionfish-impacted areas off of the southeastern United States are most prevalent off-shore near the continental shelf-break but are also common near-shore and 2) in impacted areas, lionfish have reduced tomtate (a native forage fish) abundance by 45% since the invasion began. Here, we employ a spatially replicated Before-After-Control-Impact analysis with temporal pairing to quantify for the first time the impact of the lionfish invasion on native fish abundance across a broad regional scale and over the entire duration of the lionfish invasion (1990–2014). Invasive lionfish pose an unprecedented threat to biodiversity and fisheries throughout Atlantic waters off of the southeastern United States, the Caribbean and the Gulf of Mexico.
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