Monster goldfish are breeding in Lake Tahoe

Published On: Feb 20 2013 07:58:12 AM HST

Researchers are finding a growing number of giant goldfish in Lake Tahoe, and questioning the ecological impact the fish could have on the lake.

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Christine Ngai, of the University of Nevada, Reno, was among the researchers who found the first goldfish during a survey of invasive fish in the lake.

“You just see this bright golden orange thing starting to float up, and you’re like, what is that? And then you take a net and you scoop it up and you’re like, it’s a goldfish,” Ngai said of the initial discovery.

Ngai had heard stories from fishing guides about large goldfish, but they were the first to document the species.

“Then when I saw it -- I was like, oh ...  it exists," Ngai added.

Ngai said the crew was surprised not just to find the fish, but to see how big they are.

"It’s not your average-size goldfish. So, you’re like, is that real? Oh, it's real," she told KCRA 3. "It’s alive.”

Ngai and other researchers from UNR, UC Davis, and the California State Fish and Game regularly survey fish using a specialized boat with electrical probes extending from it, which temporarily stun nearby fish.

They had been counting large-mouth bass, which are a more prolific invasive species.

“In terms of studying non-native species, that means there’s a new species that we have to look into," Ngai said.

At first, biologists would find only one goldfish on each outing. 

One day, they captured 15 in the Tahoe Keys. 

And some are pregnant.

Researchers take the goldfish and other invasive species to their lab to dissect and study what they are eating. 

“The goldfish is exemplary because it tends to consume a lot of material and excretes lots of nutrients,” University of Nevada researcher Dr. Sudeep Chandra said.

Goldfish are omnivorous. 

Biologists theorize they could eat smaller fish creating new competition for native trout. 

They also could pump nutrients as byproducts into the water and spur algae growth.

“As you know at Lake Tahoe, we’re trying to keep the lake crystal clear, and excreting nutrients like the composition of miracle grow will stimulate algae growth,” Chandra added.

And, Chandra said, there are no prior studies on goldfish to turn to for guidance. 

It's not certain how the goldfish first got into Lake Tahoe, Chandra said, but he suspects it's the result of aquarium dumping.

Policies are already in place to limit live-bait fishing, and boat inspections to limit the introduction of invasive species. 

Now, some believe a new campaign to curb aquarium dumping may be necessary.

“Those small little things that people do can have a large impact when you consider that it's probably not just one person doing it,” said Ted Thayer, of the Tahoe Regional Planning Agency.


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