Can We Stop the Invasion?

NOAA scientists collecting lionfish off the coast of North Carolina to take back to the laboratory for analysis. Click on image for larger view and further details.

Most scientists agree, it is unlikely that the lionfish's invasion of U.S. waters can be reversed. Any large-scale attempts to remove the existing lionfish from U.S. Atlantic waters appear impractical and would be very costly, because of the large geographic range and depths that the fish now occupies. Lionfish are now found along the entire southeast U.S. coastline at depths between 80 and 260 ft, making their complete removal all but impossible. Scientists point out that the introduction and spread of the lionfish illustrate the difficulty of managing introduced species in the marine environment. Lionfish now join the ranks of other aquatic invasive species that have taken up permanent residence in U.S. waters, such as European green crabs, Asian eels and zebra mussels.

Scientists are attempting to answer the following questions:

• How does an "alien invasion," like that of the lionfish, affect an ecosystem?

• Are lionfish in the Atlantic a problem?

Zebra mussels cover a water current meter in Lake Michigan near Michigan City, IN. Click on image for larger view and further details.

Although scientists don't know much about the ecological impact of lionfish in the Atlantic at this point, they know very well the impacts of many other invasive species. For example, scientists have studied one of the most infamous stowaways that has entered U.S. waters via ballast water, the zebra mussel. Originally from Europe, it now flourishes in the Great Lakes. Up to 700,000 zebra mussels may occupy only one cubic yard on the surfaces of boats, pilings and pipes. By 2000, these alien invaders had caused $5 billion damage to the infrastructure of industries, public utilities, ship navigation, boating and sport fishing.

Purple loosestrife (Lythrum salicaria), an invasive wetland plant native to Europe and Asia, has spread throughout North America. Click on image for larger view and further details.

Another example of a well-studied aquatic invader is purple loosestrife, a plant now common in wetlands throughout the U.S. and Canada. It was brought to North America from Europe in the 1800s - both accidentally and on purpose. Because it has no natural predators in North America, purple loosestrife is able to rapidly invade wetlands. Once established, purple loosestrife out competes and displaces many native species such as cattails. Because animals depend on native plants for food, nesting areas, and shelter, purple loosestrife invasions indirectly harm wildlife. Muskrats, bog turtles, and ducks are some of the species that suffer when purple loosestrife takes over.

So, what about the future of lionfish in U.S. waters?

Lionfish are often seen interacting with native species, like this squirrelfish, in their new Atlantic neighborhood. Click on image for larger view and further details.

Scientists predict that lionfish will continue to increase in abundance. In 2004, NOAA scientists collected 155 lionfish at 19 different locations. Some of these were juveniles and females ready to spawn (reproduce). These numbers far surpass their original expectations, and they now believe that lionfish are actually thriving in water depths over 120 ft off North Carolina. Scientists also predict that lionfish presence in United States waters, especially in the southeast, will become more noticeable, and more encounters between people and lionfish will probably lead to more stings. Because most observations of lionfish off the U.S. coast have been at depths of 100 ft or more, scuba divers are most likely to encounter them, but scientists caution that recreational and commercial fishermen will also be catching them in the future.

For now, scientists have five main suggestions:

• Track the lionfish population. Although more sightings in recent years suggest that more lionfish are present, that may not be the case. It could simply be that more public awareness has led to more reports. A monitoring program is needed to determine if the number of lionfish is actually growing.

During an August 2004 research expedition off the coast of North Carolina, NOAA scientists collected 28 lionfish on one shipwreck during a single dive. Click on image for larger view and further details.

• Conduct more research. Scientists' ability to predict the lionfish's future abundance, and its effects on the ecosystem is greatly hindered by a lack of knowledge. Research is needed to determine the lionfish's ability to survive, reproduce, and grow in the Atlantic Ocean.

• Educate the Public. People need to know that it can be harmful to release aquarium fishes into bodies of water. In the United States and throughout the Caribbean, people should be alerted to the presence of lionfish and encouraged to report sightings. At the same time, people should be cautioned against handling lionfish and made aware of the health risks from their stings.

• Notify physicians and other health care providers about venomous fish in U.S. waters. One study of reported lionfish stings, mostly involving aquarists, noted no fatalities. Most stings result in uncomplicated wounds with severe local pain that responds well to soaking treatment. A greater risk appears to be secondary infection resulting from the wound. In addition to medical personnel and health-care providers, boat operators and lifeguards also need to be advised about lionfish stings.

• Make regulations to control the introduction non-native marine species. Bermuda's approach, which is to enforce a strict ban on the importation of live fish, is proving an especially effective way to reduce the risk of aquarium releases. But scientists caution that the issue is more complex than simply limiting imports of non-native species. Some believe that such efforts will fail unless we learn more about how these species disperse once they are introduced into non-native waters. Although the lionfish invasion is probably here to stay, this dramatic event may prompt the development of effective strategies to reduce the ill effects of other marine invaders.

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