Study finds Tahoe unfit for Lahontan cutthroat

RENO -- Lake Tahoe is no longer a nurturing environment for Lahontan cutthroat trout that once reigned supreme in the lake's deep waters, a new scientific study has concluded.

The study conducted by the Tahoe Research Group of the University of California, Davis cites two main reasons why efforts to reintroduce the native fish would likely fail -- they'd starve or be eaten.

"We found that the food web has changed so dramatically, efforts to re-establish the Lahontan trout could be better directed to surrounding, less-impacted lakes and streams," said Brant Allen, one of the researchers on the study.

When white settlers arrived in the Tahoe Basin in the 1800s, Lahontan cutthroat were at the top of the lake's food chain, growing up to 40 pounds.

By 1939, the fish was extinct from Lake Tahoe, a victim of overfishing and habitat destruction induced by man.

During the 1997 presidential forum at Lake Tahoe, then-President Clinton listed restoring Lahontan cutthroat as one of many goals in restoring the lake that straddles the Nevada-California line in the Sierra Nevada.

But the new study concludes too much has changed at Lake Tahoe over the past 70 years to make such a goal feasible.

For one thing, Great Lakes' mackinaw, or Lake trout, were introduced and now claim the top rung of the food chain ladder.

"They grow to very large sizes," Allen said.

"If you were to reintroduce Lahontan cutthroat, it's very hard to raise them to historical sizes. ... the 15 pound fish," he said. "The hatcheries aren't equipped to raise fish that size.

"Anything you put into Tahoe would be edible-size to the Lake trout population."

The other problem is freshwater shrimp. Also introduced since cutthroat disappeared, the shrimp have eaten all the water fleas that were a primary food source for the Lahontan cutthroat.

"The assumption is, if you were to put the same species back in the lake, they would feed the same way," Allen said. "But they wouldn't be at the top of the food chain and the food they were feeding on is no longer there."

To arrive at their conclusion, scientists analyzed preserved tissue samples of cutthroat dating as far back as 1872 and reconstructed the fish's diet.

"The main message is that the exotic species have really altered the system," said Jake Vander Zanden, another researcher now at the University of Wisconsin, Madison.

"We looked at how the food web has changed and it has changed a lot," he told a Reno newspaper.

Randi Thompson, a spokeswoman for the U.S. Fish and Wildlife Service in Reno, said the agency is not ready to write off the possibility of someday reintroducing cutthroat to Lake Tahoe and called the study's findings "premature speculation."

"Who knows what can happen to the food chain in 20 years," Thompson said. "For us this is a science-driven process and we're not ready to say one way or another.

"We're 20 years out before we even look at Tahoe for reintroduction, she said. "There's a lot of ifs at this point."

The research group's study said other area lakes are more promising candidates for the fish. Scientists said they were surprised to find a thriving population of Lahontan cutthroat in nearby Cascade Lake.

"Most of the land around and access to Cascade Lake is privately owned, so it's difficult for people to get in there and introduce fish," Allen said.

Fallen Leaf Lake, where cutthroat were planted last summer as part of another scientific study, is another candidate even though that lake also has shrimp and mackinaw populations, he said.

"We're evaluating the success of those fish to see how they will survive and management tools to help them out," Allen said.