How did Teller Lake become the new weekend getaway for pet goldfish? It looks as though a handful of owners probably discarded their fish into the lake about two years ago, where they started to reproduce. Their populations grew, unchecked by predators, and they took up more and more resources in the lake, leaving less for native fish like blue gills, channel catfish, and sun fish. Invasive fish species like goldfish can also bring diseases to endemic species. To save the local ecosystem, officials have realized that they will have to take drastic measures to get rid of the goldfish before they invade other connected lakes.