“Monster goldfish” have been discovered in Lake Tahoe, and humans are to blame for the alien fish invading the ecosystem, the Huffington Post reported Thursday.

The unwelcome giant goldfish can reportedly grow up to 1.5 feet long, and since they aren’t native to the lake many believe they were dumped there from an aquarium, a news report by NBC affiliate KCRA-TV said.

The fish are thriving and breeding at a quick pace, and researchers fear their effect on the rest of Lake Tahoe's creatures.

They’re the same goldfish that can be bought in a pet store, and while it might seem hard to believe that the mutant fish were able to survive a winter in Lake Tahoe, KCRA finds they’re actually multiplying.

"We know that we have a giant goldfish. The question now becomes how long has it been there and how many others are there in the lake?" Dr. Sudeep Chandra, an associate professor at the University of Nevada, Reno, told KCRA.

According to the Huffington Post, aquarium dumping is a widespread problem across the United States and throughout the world. Various invasive species are dumped into the wild every year.

"Globally, the aquarium trade has contributed a third of the world's worst aquatic and invasive species," Sue Williams, an ecology professor at UC Davis, told the Huffington Post.

Asian carp, lionfish, nutria and northern snakehead also are invasive species that were once kept as pets but then let into the wild. They can destroy vegetation, cloud the water they occupy and eventually kill off the native species that live there.

Florida is wrestling with the Burmese python, the giant snakes that were released into the Everglades are now invading people’s backyards.

Right now the Lake Tahoe goldfish have grown to a size of 1.5 feet, but in a picture from France a goldfish looks like it grew to at least three feet long.

The goldfish were discovered in Lake Tahoe after researches used an electric probes to stun the fish and scoop up the ones the float to the surface of the water, KCRA reported.

Christine Ngai explained to reporters they found as many as 15 in one corner of the lake.

The mutant goldfish have also been found in Arizona, Michigan, Arkansas, the U.K. and France.