Stopping Invasive Species

Center for Great Lakes & Aquatic Science

For years, natural resource managers have contended with unwelcome aquatic invaders. Zebra mussels. Mitten crabs. Snakeheads. Some species fade away, but others become highly invasive, causing both economic and ecological harm.

One of the most devastating examples in the Chesapeake Bay was MSX, a parasite most likely brought to the region in the late 1950s with the imported Japanese oyster, Crassostrea gigas.

No one knows when the next unwanted invader will arrive. To get at the source of the problem, invasion biologists are now moving from a species-by-species approach — called by some "the species of the month" approach — to focus on how invasive species move from one place to another, so-called "vectors."

On December 2, 2009, Maryland Sea Grant teamed up with the Mid-Atlantic Regional Panel of the Aquatic Nuisance Species Task Force to host a workshop focused directly on examining and controlling exotic species vectors.

The daylong workshop took place in Baltimore, Maryland, and drew experts from throughout the region and beyond.

Internationally known biologist James Carlton, of Williams College, cited numbers of dramatic examples of vectors in his keynote address. He began with his students' boots.

After a fieldtrip tromping through a marsh, a long walk back on an asphalt road, and an even longer bus ride, biology students turned their boots over to Carlton for analysis. Hidden in the deep treads of their soles were more than a dozen hitchhikers from the marsh, species still alive that could easily be carried from one ecosystem to another.

Carlton also went to the web and placed orders online. He ordered blue crabs for dinner, sea squirts for biology experiments, bait for fishing. After careful analysis he found that 18 unexpected species came with the bait, a dozen species came with the crab, and 104 species came with the sea squirts.

Clearly, Carlton said, people ordering marine organisms online are getting a lot more than they expect or want.

While boots and bait may seem like small vectors, the "hitchhikers" they transport can cause harm over time. They also make Carlton's point that we are a long way from having a complete "vector inventory."

According to Carlton and other experts, we are just beginning to deal with many of these vectors, but there is one vector that's received a lot of attention: ballast water in ships.

A panel of scientists and policy experts addressed how research, regulation, planning, and technology have combined to manage the movement of invasive species through ballast water. These approaches can provide a model for coping with ship fouling and other vectors that marine species might use to travel the seas or the airways or even the footpaths.

A report is now taking shape that will summarize the workshop and set forth a series of actions and timelines for implementing a strategy that will tighten control over vectors that move invasive species around the world. For more information on the workshop and on the issue of aquatic species see www.mdsg.umd.edu/exotics.