Morris Jr., J.A.

Summary:

Lionfishes are venomous species of scorpionfishes which are native to Indo-Pacific coral reef ecosystems and adjacent habitats. Because of their colorful and dramatic appearance, they are prized by aquarists around the world. Through accidental and/or purposeful release into warm Atlantic waters, they have become established as a highly problematic alien species that poses a serious threat to coral reefs in Bermuda, Florida, the Gulf of Mexico, the Caribbean islands, Central America, and northern South America. Invasive lionfish populations can reach high densities and cause extreme disruption to native fish communities; they have been shown to reduce biodiversity, are responsible for the decline of ecologically important species, and hinder stock-rebuilding efforts for economically important species.

In January 2010, in recognition of the severity of the lionfish invasion and its impact on coral reefs and local communities, the 24th General Meeting of the International Coral Reef Initiative (ICRI) agreed to set up an Ad Hoc Committee to develop a strategic plan for the control of lionfish in the Wider Caribbean. The Strategy described in this document is one of the actions implemented by the Ad Hoc Committee, known as the Regional Lionfish Committee (RLC). It seeks to build on the existing programs and efforts aimed at minimizing the impacts of the lionfish in the region, and to provide a framework for action to provide a regionally coordinated response to the lionfish threat. The Strategy is based on the following objectives:

1. i)  Facilitate collaboration among governments, reef-reliant industries, civil society, and academia by providing mechanisms for coordination of efforts across political and geographical boundaries,
2. ii)  Encourage a coordinated research and monitoring agenda,
3. iii)  Encourage governments to review and amend relevant legislation and, if necessary, develop new regulations and policies to control lionfish,
4. iv)  Control invasive lionfish populations using regionally coordinated, effective methods, and
5. v)  Provide education, information and outreach mechanisms to generate public support and foster stewardship in invasive lionfish programs.

Each of the objectives is supported by strategies and actions with specific stakeholders identified as possible implementers. It is expected that this Strategy will be used by governments and other stakeholders to create plans to implement many of the actions identified in this strategy. The action plans would include timelines and indicators to measure effectiveness in achieving the objectives of this Strategy. Local government, coastal communities, non-governmental organizations (NGOs), and marine industries will play an important role in implementing on-ground actions to reduce lionfish impacts and enhance the resilience of reefs in the Wider Caribbean region. 

The invasion of lionfish (Pterois miles and P. volitans) may prove to be one of the greatest threats of this century to warm temperate and tropical Atlantic reefs and associated habitats. As the first marine reef fish invasive species to this region, lionfish are changing the culture of how reef managers view invasive species, the regional connectivity of marine reefs, and their vulnerability to marine invasions.

The term “lionfish” is now as notorious as the other major invaders of the last century, such as Asian carp, kudzu, zebra mussels, and sea lamprey. Originally imported into the United States as a popular aquarium fish, the lionfish is now one of the most abundant top-level predators of many reefs. Lionfish pose a threat to the integrity of the reef food web and are capable of impacting commercial fisher- ies, tourism, and overall coral reef health.

Viewed in context with other reef stressors — such as land-based pollution, climate change, and overfishing — the lionfish invasion is distinguished by two obvious characteristics.

A RAPID, WIDESPREAD INVASION

The first outstanding characteristic of the lionfish invasion is that it has occurred rapidly across a wide geographic area. The initial confirmed lionfish sighting in the United States occurred in 1985, off Dania Beach, Florida. Some 15 years later, in 2000–2001, lionfish were identified as an established invader in the offshore waters of North Carolina, United States. At the time of this writing in 2012, lionfish are fully established throughout the Southeast United States, the Caribbean Sea, and much of the Gulf of Mexico. Lionfish are expected to reach the warm temperate reefs of South America soon.

BROAD DIET AND GENERAL HABITAT

The second pronounced characteristic of lionfish is their broad diet and general habitat preferences. Because of these factors, lionfish have the potential to affect the structure and function of many Atlantic marine communities — from the sea surface to depths exceeding 300 meters, and across habitats ranging from coral and hardbottom to artificial reefs, mangroves, and seagrass beds. For example, the high densities of lionfish observed in locations such as the Bahamas may be causing an abrupt change to the biodiversity and community structure of reef fish communities, and could constitute the most significant change since the beginning of industrialized fishing (Albins and Hixon 2011). 

CASCADING IMPACTS

Alarmingly, lionfish may trigger cascading impacts through their disruption of the food web. For example, the lionfish consumption of herbivorous fishes could reduce the functional role of herbivores in keeping algae in check, a process known to be important for the health of coral reefs. Lionfish may also compete for resources — principally food and space — with economically important species, such as snapper (Lutjanids) and grouper (Epinephelids). It is uncertain if stock-rebuilding efforts will be able to return reef fish stocks to pre-lionfish abundance levels.

Lionfish could also affect the recovery of species of concern, such as the Nassau grouper (Epinephelus striatus), Warsaw grouper (E. nigritus), and speckled hind (E. drummondhayi). These species are critically low in abundance and might not recover quickly under the additional predation mortality imposed by lionfish.

Lastly, it is the interaction of the lionfish invasion with existing reef stressors that poses the greatest concern. Coral reefs of the Atlantic are already highly stressed from bleaching events, climate change, ocean acidification, overfishing, and pollution. The additional stress of this invasive species could accelerate and compound the degradation of coral reef ecosystem health in profound and unexpected ways.

LOCAL INTERVENTION IS CRITICAL

Local control efforts are critical for mitigating the effects of lionfish on key marine habitats. These efforts are invaluable for supporting other conservation initiatives, such as management of marine protected areas and fisheries stock rebuilding. The re-colonization of lionfish from remote and unmanaged habitats will continue to inflict constant stress on Atlantic marine communities. Until new technologies and approaches are developed for controlling lionfish populations, managers must be prepared for long-term intervention. 

The rapid invasion of lionfish into the Western North Atlantic and Caribbean will undoubtedly affect native reef fishes via processes such as trophic disruption and niche takeover, yet little is known about the dynamics of this invasion. We constructed a stage-based, matrix population model in which matrix elements were comprised of lower-level parameters. Lionfish vital rates were estimated from existing literature and from new field and laboratory studies. Sensitivity analysis of lower-level parameters revealed that population growth rate is most influenced by larval mortality; elasticity analysis of the matrix indicated strong influence of the adult and juvenile survival elements. Based on this model, approximately 27% of an invading adult lionfish population would have to be removed monthly for abundance to decrease. Hierarchical modeling indicated that this point estimate falls within a broad uncertainty interval which could result from imprecise estimates of life-history parameters. The model demonstrated that sustained removal efforts could be substantially more effective by targeting juveniles as well as adults.

Lionfish, Pterois volitans and P. miles, are native to the Indo-Pacific and have recently invaded the Western Atlantic Ocean. Strategies for control of this invasion have included limited removal programs and promotion of lionfish consumption at both local and commercial scales. We demonstrate that lionfish meat contains higher levels of healthy n-3 fatty acids than some frequently consumed native marine fish species. Mean lionfish fillet yield was 30.5% of the total body wet weight, a value that is similar to that of some grouper and porgy species. A sensory evaluation indicated that lionfish meet the acceptability threshold of most consumers.