Invasive fish pose threat to Lake Tahoe

RENO (AP) - Several fish species common to warm-water Midwestern lakes are thriving and spreading around Lake Tahoe, a new study found.

Sudeep Chandra, a University of Nevada, Reno assistant professor and fish expert, said a warming climate and the introduction of fish like largemouth bass and bluegill could pose a threat to the sensitive ecosystem of the Sierra lake.

Chandra said the warming climate will likely increase the spread of invasive fish because warmer temperatures near the shore will bring Lake Tahoe's waters into a range that lets the fish spawn in the lake.

"The most important findings from our study indicate that the warm-water fishes of Lake Tahoe are either competing (with) or preying upon native fishes," he said.

"Through increased warming of temperature near shore, Lake Tahoe's waters will come well into the range that allows these fish to spawn in the lake," he said.

Chandra said the good news is that fish densities monitored during the three-year study starting in 2006 are low in most locations.

If steps are taken now to manage those fish, he said, changes might be possible "before they get out of hand."

The warm-water fish, first observed at Tahoe in the 1970s, were likely introduced illegally by anglers eager for a new type of fish to catch, the report said.

Tahoe's fishery had already been vastly altered by man. Mackinaw, rainbow, brown and brook trout were introduced to the lake. The Kokanee salmon that spawn on Taylor Creek in the fall were introduced to Tahoe in the 1940s.

While bass and bluegill are most common at the Tahoe Keys marina in South Lake Tahoe and partially enclosed bays where the water is warmer, evidence suggests they are moving.

Radio signals from electronic transmitters implanted in the fish indicated some swam from Tahoe Keys into the open lake before contact was lost.

"That could mean they are spreading around the lake to other suitable habitat," said Ka Lai Christine Ngai, a researcher from the University of California, Davis' Tahoe Environmental Research Center.

Preservation of native minnows is an important ecological goal at Tahoe, and the threat posed to them by invading warm-water fish must be determined, said Elizabeth Harrison, water quality program director for the Nevada Division of State Lands.

"We're obviously trying to maintain the native fisheries that are there," Harrison said. "Until we get a good handle on this, it's hard to determine the best way to move forward."

The study was presented earlier this month to her agency.

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Information from: Reno Gazette-Journal, http://www.rgj.com