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These monster fish can grow up to 1.5 feet long and weigh more than 4 pounds! (Department of Natural Resources and Environmental Science, University of Nevada / Reno)

Giant Goldfish Invade Lake Tahoe

Scientists are trying to stop an invasive species of goldfish from taking over America’s largest mountain lake

By Jennifer Marino Walters | null null , null

How much harm can goldfish do? In some cases, a lot.

Giant goldfish—one of which measured nearly 1.5 feet long and weighed more than four pounds—have been found in Lake Tahoe, a large freshwater lake in the mountains along the border of California and Nevada. These goldfish are an invasive species—an animal or a plant that moves into an area and harms the native, or local, animals or plants that live there.

The goldfish, along with several other species of warm-water fish, could interfere with the lake’s ecosystem. They can destroy native fish by eating them or their food sources. The goldfish also excrete nutrients that fuel algae growth, which could muddy Tahoe’s clear waters.


Scientists say the goldfish were likely dumped into the lake by aquarium owners. Aquarium dumping has become a common problem in the U.S. and throughout the world.

“Globally, the aquarium trade has contributed a third of the world’s worst aquatic and invasive species,” Sue Williams, who wrote a recent report on California’s aquarium trade, told reporters.

In Lake Tahoe, invasive species have accounted for more than half of the fish surveyed since 2007. Scientists expect the number of these non-native fish to increase, partly because of climate change.

“As Lake Tahoe’s waters warm, invasive species can more easily breed in the near shore and travel to other parts of the lake,” says Sarah Muskopf, a U.S. Forest Service fish biologist.


Scientific and government groups are working together to prevent, control, and get rid of invasive species. When biologists find warm-water fish in Lake Tahoe during surveys, they remove them. But the public can play the biggest role in solving the problem.

“If we can persuade [people] not to release their aquarium fish or leftover bait fish into the lake, we will have made a critical step in addressing the problem of invasive species,” says aquatic biologist Maura Santora.

Studies have shown that size and aggressiveness are two of the biggest reasons people dump their fish. Williams suggests returning the fish to a pet shop or calling the state department of fish and wildlife instead.

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