In the United States alone, scientists estimate that about 7,000 invasive species of plants, mammals, birds, amphibians, reptiles, fish, arthropods and mollusks are established. The National Wildlife Refuge System has certainly felt the impact of these invasives, as they regularly displace or reduce native plant and animal populations.

In the 1930s, for example, a new and improved Welland Locks and Canal allowed sea lamprey to gain access to the upper Great Lakes, virtually wiping out the lake trout and whitefish of the Great Lakes within one human generation. In the 1950s, a shipment of tainted rainbow trout from Europe brought with it the parasite Myxobolus cerebralis, more commonly known as whirling disease, which became a scourge in trout hatcheries and in the wild, as outbreaks in Montana and Colorado in the 1990s well demonstrated.

More recently, commercial growers in Arkansas inadvertently released various Asian carp species. Some are now established in the Mississippi and Ohio River ecosystems and are poised to invade the Great Lakes.

How can anglers help fight non-native species?

Take the following precautions:

• Inspect and clean your boat, trailer, vehicle, waders, clothing and equipment prior to leaving your fishing area. Remove all vegetation, seeds and mud.
• Don't use non-native live bait that could become invasive.
• Drain all water from your boat, motor, bilge and livewells before leaving.
• If possible, rinse or dry your boat when leaving a water body.
• Learn how to identify invasive species and how to avoid transferring them.

Visit Protect Your Waters, a Web site for recreational users who want to help stop aquatic nuisance species.