Like the larger-than-life snakehead fish, most alien aquatic intruders don't announce their potential threat to an ecosystem until they've made themselves at home. By then, it is often too late to send them packing. But new computer models that target the Great Lakes predict which species of fish are likely to invade and whether the invasion will cause widespread damage to this region.
Most policy and scientific efforts contending with invasive species concentrate on plants and animals that have already set up shop. The few previous attempts to anticipate which species might pose a problem have considered only whether they possess certain traits, such as fast growth rate. Most studies have not attempted to quantify the risk of potential invaders based on various life history traits and invasion pathways.
In the 8 November issue of Science, fisheries biologists Cynthia Kolar of the U.S. Geological Survey in LaCrosse, Wisconsin, and David Lodge of the University of Notre Dame in Indiana present models that assess the risks associated with introduction of various fish species to the Great Lakes region. Their models include life history traits gleaned from the literature, such as reproductive success and how well other members of the genus have invaded in the past. Unlike previous efforts, Kolar and Lodge's approach breaks the invasion process into separate stages: introduction, establishment, and spread. This is critical because a trait such as fast growth might help a species get established, but it might not help it spread, for example. When Kolar and Lodge applied their models to past invasions, they found that they could predict invasion success with up to 94% accuracy.
But predicting the past is easy. Kolar and Lodge next examined 66 species that could potentially invade the Great Lakes. They identified 16 of these that would spread quickly if introduced. Of those 16, five have the potential to become established nuisance species, the authors report.
This type of modeling approach is valuable because it will help cash-strapped policymakers target high-risk species, says marine policy specialist Porter Hoagland of Woods Hole Oceanographic Institution in Massachusetts. And, as long as there are good data available, the approach is “readily applicable to other organisms, invasion pathways, and ecosystems,” adds invasion biologist Marjorie Wonham of the University of Edmonton in Alberta, Canada.