Trout Program Slashed to Save Frog

Sierra lake amphibians may be endangered by annual stocking of young fish

Glen Martin / SF Chronicle 11jan01

Reversing a policy that stretches back more than 100 years, the California Department of Fish and Game has decided to slash its program of stocking Sierra lakes with trout in an effort to protect endangered amphibians.

The move signals a dramatic shift in management of the High Sierra, one that could ultimately turn back the clock on the region's aquatic ecology. The decision also is likely to exacerbate tensions between anglers and environmentalists over management of the Sierra's high lakes.

In past decades, the department annually dumped tens of thousands of fingerling trout in Sierra lakes to provide sport for anglers and backpackers. The planting was originally done with mules, but airplanes were later used, allowing for stocking in the remotest of lakes.

Now, that will change. Pending research, stocking will be cut, probably drastically. Trout may be expunged from some lakes to give beleaguered native amphibians -- most notably the mountain yellow-legged frog -- a little breathing room.

The change in policy was driven at least in part by a petition filed by the East Bay-based Center for Biological Diversity and other groups to list the yellow-legged frog under the U.S. Endangered Species Act, state officials acknowledge.

Yellow-legged frogs have dwindled in numbers across the Sierra, where they once thrived in lakes and streams. The frogs are medium-sized, with light brown, dark-spotted backs and sunny yellow bellies and underthighs.

Many scientists think the primary reason for the decline is the teeming numbers of nonnative fish -- brook, brown and rainbow trout, primarily -- that now inhabit the Sierra's lakes. Other factors also have been suggested for the decline, including airborne pesticides from the Central Valley.

Most of the High Sierra supported no trout before white settlement of California, and the amphibians that evolved in the region's lakes were evolutionarily ill-suited to deal with predatory fish.

"Mountain yellow-legged frogs are slower to mature than most other frogs," said Tina Andolina, a conservation associate with the California Wilderness Coalition, an environmental group based in Davis. "The tadpoles take two or more years to mature into frogs, which makes them vulnerable to predation," said Andolina, "and they key into the same areas trout like -- the deep pools that don't freeze or dry up."

The frog's decline has set up a potential conflict between Sierra preservationists on one hand and recreationalists and anglers on the other. The state hopes to walk the narrow path between these two sometimes antagonistic camps.

"We're going to be using two criteria to determine whether to stock, and how much to stock if we do stock," said Diana Jacobs, a science adviser to Fish and Game director Robert Hight.

First, Jacobs said, "if a lake has a self-sustaining population of trout, we won't stock." Jacobs said the department has reduced the number of fish it has planted in fish-bearing lakes in recent years, and that policy "will probably intensify" under the new plan.

The second criterion, said Jacobs, has to do with the frogs. "Our decisions will be based on information we're gathering on native amphibians," she said, "and we'll only stock where there's no significant impact (on frogs)."

Conservationists reacted favorably to the news. "There were once 8,000 lakes across the Sierra that were fishless, and consequently teemed with yellow-legged frogs and other native amphibians," Andolina said. "Now, only about 20 percent of the Sierra's lakes are fishless. And wherever we see trout,

we also see steep declines in amphibians."

But trout advocates are wary of the new policy. "If it can be shown that frog declines can be directly attributed to the stocking of trout, then (Fish and Game's) decision is proper, fair and appropriate," said Jim Edmondson, the conservation director for California Trout, a state organization devoted to the conservation of trout fisheries.

"Unfortunately, the jury is still out," said Edmondson. "The science is not conclusive. There are indications the declines may be linked to excessive ultraviolet light (from a degraded atmospheric ozone layer) and pesticides blowing in from the Central Valley. Also, we have reliable data from lakes where fish stocking is taking place that show amphibian populations are robust. "

E-mail Glen Martin at glenmartin@sfchronicle.com