In the cold-water lakes and rivers of the Dakotas, steelhead, Chinook and coho salmon thrive and are prized gamefish for recreational anglers. These fish aren't native to the region and exist only through hatchery stocking by U.S. Fish and Wildlife Service (USFWS).
The non-native fishery has become a boon not just for anglers but for each state. Through a web of commerce connected to fishing-related expenditures, an estimated $100 million is generated annually.
Without continued stocking, these gamefish would eventually die-off because they lack the spawning habitat necessary to reproduce. And since their numbers are held in check by stocking and angling, the fish don't impact federally listed threatened and endangered native species like paddlefish and pallid sturgeon.
In this case, a balance exists between preserving native fish stocks and providing a sportfishery. Yet in other situations where non-native fish have been introduced into the aquatic habitat, native fish suffer.
Cutthroat trout in Yellowstone National Park's Yellowstone Lake are an endemic species that occurs nowhere else naturally. Along with bears and birds, anglers have been their only predators, and strict catch-and-release regulations have helped insure the trout's long-term survival.
But these fish now face a formidable predator that could decimate their population. Lake trout, voracious in appetite for the smaller cutthroat, were illegally stocked into Yellowstone Lake during the late 1980s. After thousands of years without competition or predation by other fish, the Yellowstone cutthroat's survival is now in jeopardy.
The non-native gamefish in the Dakotas and Yellowstone Lake are widely different examples of fish stocking. But each symbolizes the conflicts and benefits that can occur when people alter natural ecosystems. According to USFWS biologists, issues surrounding native and non-native fishes are extremely complex and often fuel debate between many groups.
"Judgment on native vs. non-native has to be done on a case-by-case basis," explains Mike Stempel, USFWS associate manager for fisheries in Region 6. "Non-native gamefish are not necessarily bad for native fish, and they don't always prey upon or compete with natives."
In certain instances where man has altered the habitat in some way, non-natives actually take advantage of the new ecosystem by fulfilling an unoccupied niche, Stempel adds. "But we need to recognize that proliferation of non-native fish, along with habitat disturbances, is one of the most significant causes of the decline of native fish throughout the West."
The evidence is compelling: Seventy percent of the 27 fish extinctions in North America were caused in part by non-native fish interactions. In many cases, the country's native fish populations continue to lose ground because of sportfishing's dependence on non-native fish stocking.
Growth of non-native fish stocks are a result of satisfying the demands of recreational anglers. Many states, particularly in the West, rely almost exclusively on non-native fishes to provide the angling public with fishing opportunities. Anglers generate gamecash for state fishery budgets through the purchasing of licenses, and states have tried to accommodate anglers' needs by maintaining a level of quality fishing. This has forced most states to develop stocking programs that use hatchery-reared non-native fish.
When Congress passed the federal Endangered Species Act, USFWS was mandated and given legal authority to save rare or declining species. Maintaining and recovering native fish stocks is a step toward the larger goal of maintaining overall health of the entire ecosystem, or biodiversity.
Under this type of management, a given area should have healthy populations of all fish, animals and birds that are considered native, or naturally existing prior to European settlement in America. An important guideline for management is to prevent conflicts with native species from introduced non-native species whenever possible.
Managing the nation's fisheries used to mean providing ample stocking of fish for anglers. But with alteration of habitat from dams and development, loss of water quality, introduction of fish diseases and other impacts on the aquatic environment, the job of managing today's fisheries includes conservation and recovery of native fishes. However, implementing the Endangered Species Act can conflict with the interests of various groups who see threatened and endangered species recovery as detrimental to their own pursuits.
"The real urgency is for all anglers to unite, regardless of the native vs. non-native issue, and focus on preservation of habitat, improved water quality and overall health of the entire ecosystem," Stempel says.
The decision to stock non-native fish in sensitive habitat will always carry risk, says Stempel. "If the scientific hunch is wrong and non-native fish do enter large watersheds and impact native fish, the problem is nearly irreversible. Biologists must err on the side of conservation of native fishes."
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