Risk Guide Fights Back Against Costly Aquatic Invaders

The guidelines will be used as a tool for North American resource managers to assess the risk of introducing nonnative species into a natural ecosystem.

While not all invasive species cause damage and some are even beneficial, the risk analysis must be meticulous to assess the mechanisms of species establishment and dispersal, as well as the potential impacts they may have once they are released into natural ecosystems.

Tiny zebra mussels, for example, introduced into North American waters from Europe in the late 1980s, have caused expensive problems, blocking pipes that deliver drinking and process water to cities and factories and cooling water to power plants; attaching in enormous numbers to ship and boat hulls, marine structures and navigational buoys; and covering beaches with sharp-edged mussel shells and rotting mussel flesh.

Rock with attached zebra mussels collected from shore of eastern Lake Erie. (Photo by Ron Dermott courtesy Environment Canada)

The U.S. Fish and Wildlife Service estimates the potential economic impact of the zebra mussel invasion to U.S. and Canadian water users within the Great Lakes region alone at $5 billion in the 10 year period from 2003 to 2013.

Now, slightly larger quagga mussels are invading the same Great Lakes waters that the zebra mussels have ruined.

In southwest Mexico, the unintentional introduction of a nonnative fish species, the armored catfish, into the Infiernillo reservoir has had a severe impact on local fisheries in Guerrero and Michoacan, affecting the quality of life of thousands of people at a cost to the region's economy estimated at more than $16 million per year.

Evidence shows that the most effective way to address the potentially devastating damage to the environment and the economy is to use preventive measures.

To this end, the Commission for Environmental Cooperation, created under the environmental provisions of the North American Free Trade Agreement, today released the Trinational Risk Assessment Guidelines for Aquatic Alien Invasive Species developed in cooperation with experts from Canada, Mexico and the United States.

These Guidelines were announced during the 16th International Conference on Aquatic Invasive Species, held in Montreal.

The function of the Guidelines is to present a process that can be used to evaluate recently established non-indigenous organisms, and also evaluate the risk associated with individual pathways of entry into North America such as ballast water dumped by cargo ships, aquaculture, aquarium trade, fish stocking, hull fouling, or live bait.

To test the applicability of the guidelines, the report uses two fishes as case studies: the snakehead and the plecostomus. Both were selected because their introduction pathways are related to trade, they are found in at least two of the North American countries, and there is evidence that they harm the environment and ecosystems.

"A truly comprehensive approach to alien invasive species will only come if all three countries work together to exchange scientific information and unite to provide harmonized invasive species actions to protect and control our continental biological resources," said Richard Orr, the project's U.S. lead coordinator and former deputy director of the National Invasive Species Council.

The control and eventual eradication of invasive fish populations, once established, is practically impossible, scientists say. The governments of the region's three countries are committed to building cross-border capacities to create prevention and awareness programs throughout North America.

The Guidelines point out that a risk assessment cannot determine the acceptable risk level, saying, "What risk, or how much risk, is acceptable depends on how a person, agency, or country perceives that risk."

Under existing international law each country has the right to set its own acceptable risk level as long as it maintains a degree of consistency in its risk decisions.

Orr said, "I truly believe that, if given a chance, regional international organizations such as the CEC can provide a positive example of what can be done not only for the three countries in North America but for the global community as a whole."

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