Book documents invasion of U.S. waters

The book was written by three U.S. Geological Service biologists who believe that invasive non-native fishes in the nation's waters are increasingly threatening aquatic systems

May 21, 1999
Web posted at: 3:30 PM EDT

Invasive fish species may be an important factor in the extinctions of many native fish species in the United States, according to a book published recently by the American Fisheries Society.

The book, Nonindigenous Fishes Introduced into Inland Waters of the United States, was written by three U.S. Geological Service biologists who believe that invasive non-native fishes in the nation's waters are increasingly threatening aquatic systems.

According to the book, non-native fish species are causing declines in the abundance and genetic integrity of native fish species — including highly valued game and fisheries species.

The spread of non-native plants and animals has become a serious problem both in the United States and worldwide. A number of resources are being mobilized to address this issue, particularly following the recent signing of a presidential executive order on invasive species.

Invasive alien species, introduced outside their natural range, thrive in the absence of natural predators or disease and quickly infest suitable habitats — devouring or crowding out native wildlife.

Many non-native fish in the United States were introduced by deliberate stocking, others have spread through releases of live bait or unwanted aquarium pets. Some of the most notorious species, such as the zebra mussel, ruffe and round goby, arrived in U.S. waters as stowaways in the ballast tanks of ships entering U.S. ports from overseas.

The new book provides information on more than 500 non-native fish species, including methods of introduction, ecological and economic impacts, range maps and identification aids.

According to the book's authors, over the past 50 years the number of introductions of non-native fishes has increased dramatically as a result of the rapid expansion in travel and international shipping, as well as increased interest in aquarium fishes. About 40 percent of U.S. non-native fish species come from foreign countries; the rest are species that have spread into new environments outside of their native U.S. geographic range. "Many of these transplants are just as bad or worse than those from foreign countries," says Pam Fuller, another co-author of the book and a USGS scientist in Florida.

Scientists believe that non-native species were a factor in 24 of the 30 known cases of a native fish species becoming extinct. USGS Chief Biologist Denny Fenn says that the effects of invasive fishes on endangered species and aquatic biodiversity will likely increase in the next 25 years. "They can and do impact entire ecosystems," Fenn says.

Some examples of systems affected by exotic fish species, include:

• The Great Lakes, where populations of the introduced ruffe and round goby are exploding and where introduced sea lampreys, which parasitize other fishes, have been implicated in the collapse of the lake trout fishery. Ruffe and round goby were introduced to the Great Lakes via ship ballast water, and the sea lamprey entered through the Welland Canal.
• The Desert Southwest, where a number of small endangered fish species such as sunfishes, catfishes and bullheads, are being wiped out by stocked largemouth bass and other species.
• South Florida, where populations of Asian swamp eel were discovered in 1998 in several locations, including just outside the Everglades. These fish, which are sold in the aquarium trade and may have escaped or been released into the state's waters by aquarists, are voracious predators that could threaten a number of native species.

This has become a problem for some western trout species in areas where rainbow trout have been introduced. "We are losing the genetic integrity of many of the western cutthroat subspecies," says co-author Jim Williams, also a biologist with the USGS Florida Caribbean Science Center. "Many populations are being wiped out, and once lost, they can't be replaced."

The authors hope to educate people about the magnitude of the problem.

The book is available from AFS by calling (412)741-5700.

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