The Little Kern golden trout has never wandered far from its mountain habitat, 5,000 to 9,000 feet high in the western Sierra Nevada mountains of Tulare County, California. Nor has its special habitat, tucked in the protective embrace of Sequoia National Park and a separate designated wilderness area, ever been visibly disrupted. Yet by the 1970s, the trout had vanished from all but a tiny segment of its river, surviving only above a waterfall separating it from the lower reaches of the Kern River's western branch, known as the Little Kern.
The trout was succumbing not to habitat loss but to what has been called the Frankenstein effect. As early as the 1870s, wildlife managers advocated bringing new species into state waters, and the San Francisco Fish and Acclimatization Society, predecessor to the California Department of Fish and Game (CDFG), began to introduce nonnative fish. But such efforts to improve the state's fisheries produced a monstrous situation for native species. The endemic trout were gradually being absorbed into the introduced genetic stock.
During the 1930s and 1940s, the Little Kern became the victim of CDFG efforts to stock nonnative rainbow, brook, and brown trout in response to anglers' claims that their catches had declined. By the mid-1940s, evidence emerged that hatchery-raised rainbow trout were interbreeding with Little Kern golden trout. Although the stocking was halted, the genetic infiltration had begun. By the early 1970s, genetically pure Little Kern golden trout persisted only in a fraction of their original range, which was tiny to begin with.
Designated California State's freshwater fish, the "golden trout" assemblage actually consists of three subspecies -- the Little Kern golden trout, the Volcano Creek golden trout, and the Kern River rainbow. All are apparently descended from coastal rainbow trout, which inhabited most of the western Sierra Nevada rivers and streams before the last ice age about 20,000 years ago. During the ice age, glaciers eliminated fish species from most alpine streams, but the Kern River's drainage was an exception. Cut off from their ancestors, the trout there flourished. Rapidly rising mountains created isolated pockets during that period, prompting the evolution of the three subspecies. While the Little Kern trout established itself in the river's western fork, the Volcano Creek golden trout is native to the southern fork, and the closely related but less colorful Kern River rainbow trout lives in the main portion of the river.
In 1965, more than a decade before its federal listing as a threatened species, California and federal agencies developed a management plan to restore the trout to the entire Little Kern drainage. Eliminating hybrid and nonnative fish with toxicants and replacing them with pure stocks of hatchery-raised Little Kern golden trout has nearly completely returned the Little Kern golden trout to about 70 percent of its original range. Newly constructed barriers prevent recolonization by nonnatives.
"The Little Kern golden trout is recovering from its dance with extinction," says Peter Moyle of the University of California at Davis, who says he is skeptical that the fish can ever be delisted, given its limited range. According to Moyle, ongoing conservation efforts will be needed. Anglers may move nonnative trout back into the streams. Or the tenuous barriers keeping nonnative trout at bay can crumble or wash out. An earthquake could break the barriers in a few short moments.
In other words, it will always be necessary to guard against the invaders at the gate. Survival threats, both man-made and natural, mean that the trout is likely to last only as long as the human vigilance over it.