Trade is the most important vector for exotic species, providing a speedy and easy means of transport for species that would not otherwise travel. Shipping containers and ballast water are two common transport mechanisms for exotics. Along with these unintentional introductions of exotic species, some states have purposefully introduced exotic species. For example, game species such as trout and pheasant have been routinely introduced in many states. However, the introduction of exotic trout species in the Southwest has led in part to a significant decline of native fish species, over 70 percent of which are now currently threatened, endangered or already extinct.
States have broad powers to regulate the import and export of species.
States can control the entry of exotics across state borders and the release of exotics within a state. States lack, however, the ability to stop the importation and release of a potentially harmful exotic species in a neighboring state. Increased state attention to the problem of controlling exotics is needed as part of a comprehensive biodiversity program. The most successful exotic species do well in disturbed habitats, have opportunistic feeding patterns, disperse quickly and reproduce rapidly. Therefore, the first step in any state program is closer monitoring of the introduction and spread of exotics within its borders.