Non-native fish stocking spelled doom for cutthroat trout |

Non-native fish stocking spelled doom for cutthroat trout

The Associated Press

In the late 1800s, when native trout were being pulled from Lake Tahoe by the ton and the local newspaper offered a subscription to anyone catching more than 50 in a day, anglers replaced their bounty with a gift.

Brook trout were the first dumped into the lake to join a teeming population of Lahontan cutthroats. Great Lakes mackinaw, rainbow trout and kokanee salmon came later.

After all, folks reasoned at the time, how could more fish be anything but good?

They were trouble instead, part of a human-caused imbalance that threw Tahoe’s aquatic ecosystem into a spin and caused the lake’s native cutthroat trout to disappear within 60 years.

More than a century later, the problem continues across the region. California officials triggered a political firefight at Lake Davis in 1997 when they poisoned the lake to kill off the northern pike, an aggressive nonnative fish believed to have been planted by rogue anglers. Efforts to battle the imported fish continue today.

“When we insert a new, nonnative species into our natural ecosystem, either intentionally or accidentally, it’s the equivalent of lobbing an environmental hand grenade,” said Dennis Murphy, a biology research professor at the University of Nevada, Reno.

“There are always ramifications,” Murphy said. “And they are almost always negative.”

For Tahoe’s Lahontan cutthroats, man-made changes to the environment spelled disaster.

Nevada’s state fish, the cutthroats once lived in all the major rivers and lakes on the eastern side of the Sierra Nevada. They were famous for their size and taste, with explorer John Fremont declaring in 1845 that “their flavor was excellent, superior, in fact, to that of any fish I have ever known.”

Lahontan cutthroats were fished extensively from Lake Tahoe and Pyramid Lake. Rail cars full of the fish were sent to mining camps and to San Francisco as people harvested a succulent resource that the Tahoe Tattler reported in 1881 was “inexhaustible.”

That was not the case. Overfishing, destruction of spawning habitat and the introduction of nonnative game fish, particularly the mackinaw, combined to cause the collapse of the cutthroat population in Lake Tahoe, with the fish gone from the lake by 1939. By 1944, cutthroats had disappeared from Pyramid Lake as well.

Efforts are under way to reintroduce the Lahontan cutthroat trout in Pyramid Lake and along the Truckee River and Walker River watersheds. And while officials with U.S. Fish and Wildlife Service hope to restore the fish to Lake Tahoe someday, that goal is probably decades away.

One problem: Vast populations of nonnative fish thrive in the lake.

A far more immediate battle is being waged in Lake Davis, a popular mountain fishing lake northwest of Reno. The northern pike, common elsewhere in the country and popular for their fighting ability, were likely planted there by fishermen, said Ivan Paulsen, a senior biologist with the California Department of Fish and Game.

“The pike didn’t fly there,” Paulsen said. “In all likelihood somebody brought them in.”

In 1997, the California Department of Fish and Game sparked a high-profile controversy by dumping thousands of pounds of fish poison into the lake to eradicate the pike. The move prompted impassioned protests by Portola-area residents and brought rifle-wielding police to the normally quiet community.

It also didn’t work, with northern pike again found in Lake Davis two years later. Biologists, concerned the aggressive fish could escape downstream and decimate trout and salmon fisheries in the Sacramento-San Joaquin Delta, continue efforts to remove the pike from the only California lake in which they’re now known to exist.

In April, officials tested the use of underwater blasting cord as part of that program.

The effort is well worth time, money and political headaches, said UNR’s Murphy.

“We’ve got some very simple ecosystems and they can be thrown out of balance very easily,” he said. “Invaders like the pike get a toehold before we know it’s there and the problem can become immense.”

Murphy also sees irony in the situation, noting that as state biologists battle the pike at Lake Davis they are also intentionally planting nonnative game fish in many other lakes and streams.

“Like Johnny Appleseed, we’ve scattered the seeds of species across our landscape without having much sense at all about the ramifications,” Murphy said.

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