Valley parks may poison trout to save frogs
Published online on Sunday, Oct. 25, 2009
By Mark Grossi / The Fresno Bee
The National Park Service wants to poison trout in some high-country lakes and streams to save a native species of frog. But some outdoor and environmental groups are worried.
The trout were planted years ago by wildlife agencies in the Sequoia and Kings Canyon national parks. They eat mountain yellow-legged frogs, contributing to a 90% decline in the species throughout the Sierra.
A preliminary project to eradicate trout from 11 lakes in the two parks since 2001 has yielded dramatic results: Yellow-legged frogs have made spectacular rebounds at these lakes.
Now National Park Service officials want to broaden the campaign throughout the two parks -- while leaving the fish in many lakes that are popular with anglers.
Removing the non-native trout does more than help the frog, park officials say. It also brings back other animals up and down the food chain that are eaten by or compete with the fish, including insects, reptiles, birds and even coyotes.
Still, the idea of national park officials poisoning trout worries groups such as High Sierra Hikers Association, California Trout and Californians for Alternatives to Toxics.
Putting poison in lakes and streams also will kill insects and amphibians and alter the ecosystem, said attorney Julia Olson, representing several groups. She said park officials should consider alternative methods.
Fish also would be captured with nets or killed with electrical shocks, officials said. But those methods are impractical for lengthy stretches of streams, marshes and larger lakes, they said. The poison -- which is not harmful to humans -- is preferable in those situations.
A summary of public comments from initial discussions of the proposal is available online. The public is invited to comment by Nov. 21.
A draft environmental study outlining possible problems and project alternatives probably will be available next year. If the project is approved, it will take many years to complete.
Park scientists say their proposed fish removal would take place in 30 to 80 lakes -- a fraction of the 575 high-country lakes where researchers found the frogs have fatal encounters with trout.
Trout removal from 11 of these lakes since 2001 has served as a kind of pilot project, said Danny Boiano, a park aquatic ecologist. After trout were removed from one lake, frogs moved in from surrounding lakes and boosted the tadpole population from 50 to 14,000 in three years, he said.
Insects, such as water boatman and mayflies, began showing up in bigger numbers because they were no longer on the menu for trout. And more snakes, birds, weasels and coyotes began feeding on the frogs.
"It's amazing," Boiano said. "Based on the success of this preliminary restoration, we wanted to propose this on a larger scale across the park."
The poisoning is what bothers critics, who say amphibians such as the yellow-legged frog are declining for many reasons, including habitat loss, pesticides, ozone pollution, ultraviolet radiation and climate change.
Critics say another factor in the decline is a deadly pathogen known as chytrid fungus that has decimated amphibians across the Sierra and other places in the world.
Scientists disagree on which cause might be the core problem, but amphibians are especially susceptible to poison, pollution and disease because they can breathe through their skin.
If lakes and streams are poisoned, all gill-breathing creatures, including tadpoles of the yellow-legged frogs, will die along with fish and many insects. Mammals, birds and reptiles are not affected if the poison is applied in the proper amounts.
But wildlife agencies have used poison for many years to remove unwanted fish from lakes. In the past, voracious predators such as white bass and northern pike have been killed with poison.
Decades ago, state and federal officials planted the trout in otherwise fishless lakes in Sequoia and Kings Canyon, as well as many other Sierra sites over the last century, as part of an effort to attract tourists.
The fish planting was curtailed in the 1970s and stopped altogether in the late 1980s. But by then, rainbow, brook and rainbow-golden hybrid trout were well-established and coveted by fishing enthusiasts.
For the proposed trout removals in Sequoia and Kings Canyon, officials will try to avoid popular fishing lakes, such as Wallace Lake in the Kern River watershed, said Boiano.
"Many people have given us lists of lakes that they want us to avoid," he said. "We're only talking about restoring up to 15% of the lakes we've identified."