What is an invasive species and why are they a problem?

An invasive species is a non-indigenous organism that adversely affects natural habitats and bioregions. Invasive introductions often result from careless human activity whether intentional or accidental, the results of which are likely to cause economic, environmental and/or ecological harm. While all species compete to survive, invasive species appear to have specific traits or combinations of specific traits that allow them to out-compete native species. Sometimes they simply have the ability to grow and reproduce more rapidly than native species; other times it’s more complex, involving a multiplex of traits and interactions.

Common invasive species traits include: Fast growth rates, rapid/frequent reproduction, high dispersal ability, phenotypic plasticity (the ability to alter one’s growth form to suit current conditions), tolerance of a wide range of environmental conditions (generalist), and the ability to live off of a wide range of food types (generalist).

Invasive species often coexist with native species for an extended time, and gradually the superior competitive ability of an invasive species becomes apparent as its population grows larger and denser and it adapts to its new location. (Note: Because the introduction of invasives is not a naturally occurring process, it does not fall under the umbrella of natural selection or survival of the fittest). With the introduction of a species into an ecosystem that can multiply and spread faster than the native species, the balance is changed and the resources that would have been used by the native species are now utilized by an invader. This impacts the ecosystem and changes its composition of organisms and their use of available resources.

Economic costs from invasive species can occur through loss of recreational and tourism revenues. This is a particularly the case with the invasive Pterois volitans (lionfish) on Roatan where so much revenue is dependent on the tourism industry. When economic costs of invasions are calculated as production loss and management costs, they are low because they do not consider environmental damage; if monetary values were assigned to the extinction of species, loss in biodiversity, and loss of ecosystem services, costs from impacts of invasive species would drastically increase.

The Roatan Marine Park Invasive Lionfish Control Program

In an effort to reduce the destructive impact of the invasive Pterois volitans (lionfish) on the coral reef ecosystem of Roatan, the Roatan Marine Park has employed a proactive stance, directly engaging the community in controlling the proliferation of this species. The RMP Invasive Lionfish Control Program focuses on the dissemination of information through educational workshops that cover topics such as; lionfish ecology, potential impacts of lionfish infestations both environmentally and economically, first-aid treatment, and goals of the program immediate and future. Following workshops, members of the community are asked to participate in the program by reporting to the RMP specific locations of lionfish sightings that include approximate depth, and size of the fish. The RMP is using this assistance from the community to manage an island-wide database of all sightings of lionfish. Information from the database is forwarded to the United States Geological Survey (USGS) who are tracking and monitoring lionfish progression throughout the Caribbean.

To increase the success of lionfish cullings, the Marine Park requested and received permission from DIGIPESCA (the governing agency for fisheries in Honduras) to distribute spears within the community to be used exclusively on lionfish to aid in controlling the population. DIGIPESCA delegated authority to the Marine Park to develop the program and regulate and enforce the agreed upon rules of the program as discussed between the two agencies. Together, with the help of participants in this program, the RMP is hopeful it can manageably control the population of lionfish within the marine reserve and thus reduce their destructive impacts on Roatans’ reef habitat.

In addition to the above mentioned roles, the RMP is also aiding in marine research on lionfish through the collection of this species at various locations around the island. Fish collected by the RMP are measured, weighed, and tissue samples are preserved in alcohol to be sent to the National Oceanic and Atmospheric Administration (NOAA) in the United States where there they will be conducting genetic analysis on this species in an attempt to learn more about specific dispersal patterns.

Did you know…?

• Lionfish were accidentally released into the Atlantic from Biscayne Bay Florida in 1992 following hurricane Andrew. Genetic analysis reveals that lionfish in the Caribbean have likely all originated from this population
• Lionfish in their native waters reproduce once per year, but with the consistent warm temperatures of the Caribbean they reproduce monthly
• Gelatinous egg masses float to the surface and planktonic larvae drift for up to 40 days before settling, allowing for wide-range distribution by ocean winds and currents
• Venomous dorsal, ventral, and anal spines prevent local predator fish from consuming lionfish
• Specialized swim bladder muscles allow lionfish to orient themselves horizontally, vertically, and upside down in the water
• Lionfish exhibit opportunistic feeding behaviors and in addition to fish, feed on a variety of invertebrates and crustaceans
• Lionfish are suction feeders that consume their prey whole and are capable of eating creatures up to half their own body size
• Lionfish population densities in non-native waters have been found to be as much as 15 times higher than in their native waters
• Studies of lionfish on experimental reefs in the Bahamas have shown a reduction in the recruitment of coral reef fishes by nearly 80 percent