INCLINE VILLAGE, Nev. (AP) - Scientists are tracking 14 fish at Lake Tahoe to study their movements and try to prevent their species from spreading out across the lake and upsetting its delicate ecology.
Large mouth bass and bluegill typically are found in much warmer waters. Researchers believe they were introduced into Lake Tahoe by
people about 15 years ago.
If left unchecked, scientists said they could significantly threaten Tahoe's cold water fishery.
"If you don't tackle them early, they just proliferate," said Sudeep Chandra, an expert in fresh water sciences for University of Nevada, Reno.
Joined by scientists from University of California, Davis in a program supported by the U.S. Forest Service and the California Department of Fish and Game, Chandra and colleagues are tracing movements of the fish through next winter.
Likely introduced by anglers in the Tahoe Keys area of South Lake Tahoe roughly 15 years ago, bass and bluegill appear to be spreading around the lake slowly but steadily.
The fish have overrun the Keys and have been found in more than half of the marinas and lagoons sampled around the lake.
"We know they are basically all the way around the lake," said Brant Allen, staff researcher for UC Davis. "They are widely distributed but their populations are still very low outside of the Keys."
Signals from the surgically implanted transmitters are picked up by receivers on the lake bottom and by a mobile receiver on a research boat.
By finding out more about how the fish move, scientists say they can get a better idea on how they might prevent further spread of these warm water fish.
The main threat from the nonnative fish is to Tahoe's native minnows, Lahontan red side shiners, speckled dace and tui chub. Large-mouth bass eat the minnows while bluegills compete for the aquatic invertebrates minnows need for food.
Minnows - which warm-water fish have eradicated from the Tahoe Keys - play an key role in Lake Tahoe's food chain but saving them is important for other reasons as well.
"It's also somewhat of an ethical question," Allen said. "These are some of our last native species still left in Tahoe."
Other fish now flourishing in the lake such as Mackinaw, rainbow and brown trout and Kokanee salmon were introduced by humans.
If minnows were to disappear, Chandra said a goal to return native Lahontan cutthroat trout to Tahoe would likely be impossible.
"How can you even imagine doing that if there's no food source for them," he said.
If the study indicates Tahoe's warm water fish are primarily originating from the Tahoe Keys, it may be possible to electroshock the area every few years and prevent their spread elsewhere around the lake, scientists said.
"The good news is Tahoe is in its early invasion process and I think we can still do something about it," Chandra said.
"You'll never be able to eradicate them but you might be able to control the population."
(Copyright 2008 by The Associated Press. All Rights Reserved.)