Effects of Invasive Lionfish on Coral Reef Biodiversity, by Danielle Goldberg

Originating from the native habitats of the Indo-Pacific region, invasive lionfish were first reported off Florida’s coast in 1985 (Côté, 2013). It is most likely that lionfish were introduced through the intentional or accidental release of captive specimens from aquaria (Semmens et al., 2004). Since then, populations of this non-native predator have grown exponentially from the US east coast through the Caribbean Sea (Figure 1). This non-native species has become a nuisance for a vast number of ecosystems. Having few predators, an annual fecundity of greater than two million eggs (Morris, 2009), and a varied diet, lionfish have become the first non-native marine fish to become established in the U.S. and Caribbean, and are now found in every major marine habitat from 0 to 300m depth between North Carolina and South America (Morris et al., 2012). Two species of invasive lionfish (Pterois miles and P. volitans) have caused many negative effects on coral reef biodiversity in Florida and the Bahamas and action must be taken to reduce their numbers to sustain the coral reef ecosystem and the associated species.

Fig 1. Rapid population growth of invasive lionfish from 1985 to 2014 (US Geological Survey/Florida Fish and Wildlife Conservation Commission)

The two species of lionfish have venomous and potentially fatal dorsal, anal, and pelvic spines, which aid in their defensive strategy against other species (Figure 2). These characteristics have thought to reduce the numbers of natural predators, further increasing their population numbers (Allen & Eschmeyer, 1973). When feeding, observational studies have shown that they use their oversized pectoral fins to herd and corner their prey, and then attack with a rapid strike (Allen & Eschmeyer 1973; Fishelson, 1997). Lionfish are both habitat and diet generalists, which further aids in their rapid growth. During a controlled field experiment, observational research showed a large adult lionfish consuming over 20 small wrasses, Halichoeres bivittatus, during a 30 min period (Albins and Hixon, 2008). These factors plus their high fecundity have added up to the “perfect storm” of characteristics of an invasive species, making it almost impossible to manage. 

 Fig 2. An invasive lionfish exhibiting it many spines, which aid in its defense strategy.  Source.    

Lionfish have decreased survival of a wide range of reef species via both predation and competition (Albins and Hixon, 2008). High densities of lionfish pose a threat to the ecology and dynamics of multiple habitats from estuaries to coral reefs, potentially leading to reduced abundances of native species and increased competition for food (Barbour et al., 2010). These predators can greatly reduce recruitment of native reef fishes (Albins and Hixon, 2008; Green et al. 2012; Albins 2013), including the juveniles of species known to be important for reef resilience (Morris and Akins, 2009). Lionfish have also reduced numbers of important herbivorous reef species, such as wrasses and parrotfish, which could have detrimental effects on already threatened coral reef ecosystems. 

Research conducted over a five-week period in the Bahamas showed significant reductions in the recruitment of native fishes by an average of 79% (Albins and Hixon, 2008). According to this study, four of the five species of parrotfish (Family Scaridae), which recruited to both lionfish and control reefs, suffered reduced recruitment in the presence of lionfish (Albins and Hixon, 2008). A separate study exhibited an increase in lionfish abundance coinciding with a 65% decline in the biomass of the lionfish's 42 Atlantic prey fishes in just two years (Green, 2012). Furthermore, this study indicated that ninety percent of the prey consumed by lionfish were small-bodied reef fishes from 42 species (Figure 3) (Green, 2012). 

Fig. 3 The percent change in biomass of native fishes between 2008 and 2010 on New Providence, Bahamas coral reef sites (Green, 2012).

This large reduction in recruitment suggests that lionfish may compete with native species by dominating this important food resource (Williams & Polunin, 2001). Lionfish not only consume, but also threaten significant fish species, specifically snapper and grouper populations, through competition for prey, which can lead to negative effects on those important commercial and recreational fisheries. Additionally, lionfish may potentially cause more harm to the already threatened coral reef ecosystem. Climate change, overfishing, and pollution are already stressors of coral reefs, and now this invasive species may add to the damage. The decrease in abundance of ecologically important species, such as parrotfish, may pose detrimental effects on corals considering these species are crucial for preventing seaweeds from overgrowing on corals (Mumby et al., 2006).

The reduced biodiversity, enhanced algal overgrowth of corals, and the possibility of envenomation from their spines can compromise the attractiveness of popular dive sites, which generates greater than US $2.1 billion per year in the United States (Morris and Whitfield, 2009; Burke and Maddens, 2004). Thus, it is imperative to reduce invasive lionfish populations before they cause even greater negative effects on a larger scale, including the economy. Unfortunately, the current geographic extent and rapid population growth of lionfish in the Atlantic makes complete eradication of this invasive species untenable (Albins and Hixon, 2008).

 However, one proposed method to control the fast-growing invasive lionfish population is through local removal of lionfish by recreational and commercial spearfishers (Barbour et al., 2010; Morris et al., 2012). Federal agencies, non-profit organizations and international organizations such as NOAA, REEF, and the International Coral Reef Initiative (ICRI) have contributed greatly to the development of means for lionfish control and management through education, lionfish workshops, and research trips (Randall et al., 2011). Additionally, lionfish derbies have become very popular in Florida and have added to increased awareness and significant reduction of the numbers of lionfish with roughly 16,134 lionfish removed in all of REEF Derbies (REEF, 2012). These derbies further provide samples for research and develop markets to continue a commercial fishery for lionfish. Interestingly, a variety of lionfish cookbooks have been produced to promote human consumption to help eradicate this species and lionfish filets are now being sold in Florida’s local grocery stores. 

The reduced biodiversity and population of various essential fish species caused by these invasive lionfish result in many negative anthropogenic and biological impacts. The presence of lionfish in Florida and the Bahamas continues to reduce biodiversity, result in important coral reef habitat loss, and pose many negative economic costs. If lionfish populations continue to grow, many recreational and commercial fisheries will be hurt, important dive sites may be compromised and overall trophic levels will be negatively skewed. Action must be taken to reduce their numbers through spearfishing, lionfish derbies, and educational workshops to inform the public about this ongoing problem. Promoting a recreational and commercial fishery for these fish would not completely eradicate the species, but would greatly reduce their numbers and aid to the conservation of the coral reefs and the associated species. 

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