Planning a vacay to Lake Tahoe? You may well encounter goldfish that are 1.5 feet long and weigh more than 4 pounds, Scientific American reports. Researchers trolling for invasive species encountered the massive goldfish and say pet owners may have dumped them. That act of good will, however, could damage the lake's ecosystem when the goldfish eat native species and excrete a nutrient that muddies the water by causing algal blooms.
So-called fish dumping is nothing new: "Globally, the aquarium trade has contributed a third of the world's worst aquatic and invasive species," says the lead author of a report on California's aquarium trade. Owners often discard them because the fish are too big and aggressive, he adds. As for the monster goldfish, only 15 have been found so far, swimming "in a nice corner," says a scientist. "It's an indication that they were schooling and spawning." (Read more goldfish stories.)