Invasive Species
Gray's Reef

Impacts from invasive lionfish could include direct competition with large groupers for food and predation on smaller sea basses, juvenile grouper, and other benthic fish and crustaceans. Credit: NOAA

Why is it a concern?

Scientific surveys of Gray's Reef have revealed the presence of several invasive species within sanctuary boundaries. Small numbers of lionfish have been observed at depth on hardbottom reefs inside the sanctuary, although they are not thought to overwinter due to low water temperatures.  Since January 2008, three invasive species were found attached to the data buoy in GRNMS: Megabalanus coccopoma (titan acorn barnacle), Perna viridis (Asian green mussels), and Tubastraea coccinea (orange cup coral). All of these species are not native to the Atlantic and have only been documented on manmade structures within the sanctuary. 

Potential impacts as a result of establishments of these and other organisms include competition with native species for food and space, predation, and introduction of disease. Impacts from lionfish could include direct competition with large groupers for food and predation on smaller sea basses, juvenile grouper, and other benthic fish and crustaceans.  Titan acorn barnacles could exclude other epifaunal species, including local barnacles, mussels, oysters, corals and sponges.

Currently, there are no documented impacts to native populations from these invasive species, but there are concerns that sanctuary resources could be at risk as ocean temperatures raise with climate change. Gray's Reef sanctuary staff will continue working with partners to monitor for signs of invasive species in the sanctuary or encroachment of species known to be outside the sanctuary. This monitoring could also provide early warning to other coastal communities at risk to invasive species in the region.

One individual lionfish (P. volitans or P. miles) was documented during annual monitoring in 2007.  Since then, numbers of lionfish sighted on transects and other underwater operations have varied: 28 in 2012, 15 in 2013, and seven in 2014. Thought to be controlled by cold winter temperatures, lionfish pose an unknown threat to fish and benthic communities in GRNMS, particularly when considering warming temperatures of climate change.

An invasive marine barnacle, Megabalanus coccopoma, was discovered on the Gray's Reef buoy in 2006.  Since then, sampling of sites along the southeastern coastline (onshore, Gray's Reef buoy, and offshore navy towers) has also identified another species of Magabalanus also invasive to the Atlantic coast. 

Overview of Research

Project Name PI and contacts Links

Research Area Monitoring

Gray's Reef NMS

Invertebrate Disturbance Monitoring

Georgia Southern University


Science Needs and Questions

  • What species represent the biggest threat to GRNMS?
  • What impacts are invasive species having on sanctuary resources?
  • What are the sources of invasive species coming to GRNMS?
  • What effective controls are currently available for these marine invasive species?
  • Are the invasive species already established spreading, and if so, at what rate?
  • Do markers buoys promote invasive species introductions (by providing a direct route to the bottom for settling organisms)?
  • How is the lionfish population changing in the sanctuary?
  • To what extent do seasonal changes in oceanographic conditions control lionfish populations at Gray's Reef?
  • At what point is removal of lionfish needed at Gray's Reef to limit impacts to native populations?
  • How much effort is required to control lionfish in the GRNMS, and is this effort sustainable?   

Education and Outreach Material

Gray's Reef has ongoing collaborations for outreach and education about lionfish.  Staff uses lionfish as a tool to teach constituents about invasive species.  They also use them to address other topics such as hard bottom ecology and marine conservation generally.  The sanctuary has worked with the Reef Environmental Education Foundation in the past on training for lionfish collection and handling, and on “Eat Lionfish” campaigns, and with the Georgia Aquarium and the Savannah Film Festival on displays, social media and public outreach events.


Office of National Marine Sanctuaries. 2012. Gray's Reef National Marine Sanctuary Condition Report Addendum 2012. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries, Silver Spring, MD. 37 pp.

Ruiz-Carus, R., R.E. Matheson, D.E. Roberts and P.E. Whitfield. 2006. The western Pacific red lionfish, Pterois volitans (Scorpaenidae). In: Florida: Evidence for reproduction and parasitism in the first exotic marine fish established in state waters. Biol. Conserv. 128(March):384-390.