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Out with a Roar

Invasive lionfish mitigation on South Caicos.

By Anela Akiona, School for Field Studies Center for Marine Resource Management

Invasive species are a major threat to ecosystem stability and biodiversity and the environmental and economic costs are increasing. While most invasions to date have been in terrestrial and freshwater systems, marine invasions have significantly increased. This has been facilitated by the expansion of international trade and travel and technological advances that make it easier for species to be transported out of their natural range.

Lion fish are more conspicuous around sunrise and sunset.

Lion fish are more conspicuous around sunrise and sunset.

The red lionfish (Pterois volitans/miles) is a popular aquarium fish from the ornamental fish trade. Several were accidentally released in Florida waters in the early 1990s (Whitfield et al. 2002) and established themselves on Atlantic and Caribbean coral reefs. The lionfish introduction is the fastest documented invasion of a marine fish, and they are now recognized as one of the world’s top conservation issues (Sutherland et al. 2010).
A native of the Indo-Pacific, lionfish have high growth and reproductive rates, spawning year round with fecundity (reproductive productivity) of over two million eggs per female. They are unique and effective predators, whose cryptic coloration and elongated pectoral fin rays provide both camouflage and a mechanism for herding prey. Lionfish also shoot jets of water at prey, which may increase the chance of a headfirst capture or overwhelm the prey’s lateral line system (sense organs used to detect movement), masking the incoming attack. This novel hunting tactic enables lionfish to consume native fishes at an average rate of 1–2 prey per hour and allows lionfish to reach densities nearly five times higher in their new range than that in their native range.
Lionfish compete with native predators for food, resources, and shelter on the reef, growing significantly faster than other predatory species such as economically important groupers and snappers. One model showed that lionfish could replace sharks as top predators and impact food web biomass, destabilizing the system (Arias-Gonzales 2011). Furthermore, lionfish cause a reduction in overall species richness (number of species) and cause a greater reduction of coral reef fishes than native predators do, including species such as parrotfish, which are critical in maintaining a healthy reef. Lionfish have been shown to reduce the recruitment of native fishes by up to 79% (Albins & Hixon 2008). The synergistic predation of both lionfish and native predators has the greatest effect on reef fish communities, and these impacts have far-reaching implications in Caribbean food webs, increasing stress on an already fragile ecosystem.
Lionfish settle preferentially in shallow habitats (mangroves and seagrasses) and then as they grow move to deep reefs. Thus far, management efforts in the Caribbean have been unsuccessful; lionfish have been shown to exhibit high site fidelity, and thus any removed individuals are replaced through recruitment alone. Targeted removals on deep terraces would likely return the maximum conservation benefits. Fishers have noted native groupers preying on lionfish with some regularity, and while there have been some recorded instances of this, most potential predators have been heavily fished and thus are unlikely to control lionfish populations (Maljkovic & Leeuwen 2008). Furthermore, the scope of the invasion and the multitude of political systems in the Caribbean make it unlikely that policy alone will be able to control lionfish populations.
The ecosystems around South Caicos support many commercially important species and provide an ideal environment for all lionfish life stages. The first document lionfish was in 2007 (Claydon et al. 2012). With this in mind, the School for Field Studies (SFS) Center for Marine Resource Studies (CMRS) launched a project to reduce the lionfish population and thus damage to reef communities around South Caicos. The project follows a multi-year study conducted by SFS CMRS staff and students from 2007–2010, which both surveyed and captured lionfish, aiming to characterize their habitat usage and reconstruct the invasion around South Caicos.
The study chronicled the settlement of lionfish, finding that juveniles settle first in shallow habitats (seagrass beds and mangrove forests), and then move to deep reefs as they mature. The current project focuses on lionfish removal and population size in order to reduce their impact on local reef fish communities. At depths of up to 30 meters, lionfish are captured from the Admiral Cockburn Land and Sea National Park. This protected area encompasses part of the “wall” (where the Caicos Bank drops off hundreds of meters) and thus is an ideal habitat for lionfish. Since they are not frightened by the presence of humans, the hardest part of removing lionfish from the reefs is usually locating them!
As lionfish have 18 venomous spines, it is very important to handle them safely. The research team uses a Zookeeper Lionfish Containment Unit (www.zkstore.com) to transport lionfish from the water back to land, where standard weight and length measurements are taken. Researchers are careful to use sturdy, puncture- resistant gloves while handling the lionfish and, once the measurements are taken, cut off all spines and fin rays from each individual. In the spirit of recycling, the spines and fin rays are dried in the sun (which renders the venom harmless and can also be done in an oven) and then used by SFS students to make jewelry. Since lionfish flesh is non-toxic and very delicious, the meat is served to SFS staff and students and during community events.
Since the conclusion of the initial lionfish study in 2010, there has been approximately a 7 cm increase in the average size of lionfish captured; the current work has already removed over 170 lionfish from South Caicos reefs in just a few months. Hopefully, other lionfish will be slow to recolonize these areas, which will free up resources for commercially important predatory fishes. By targeting the largest, most conspicuous lionfish, this study also reduces the number of larvae being dispersed and will slow the establishment of lionfish populations elsewhere.
The combination of overfishing of important reef species, warming seas, and climate change has put reefs under increasing stress. Removing lionfish, and working to understand their preferences and behaviour, can reduce at least one of the stressors on South Caicos’ most important and historic industry. While this is the only on-going lionfish project on South Caicos, SFS CMRS hopes to encourage residents to safely remove lionfish from all over the Turks & Caicos Islands, and thus work towards greater marine stewardship and sustainable fisheries.

To learn more about the SFS program, go to www.fieldstudies.org/tci.



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