Goldfish originate from the Far East and have since then been introduced into the rivers, streams and ponds or Europe and the Americas. In most areas, wild goldfish are an invasive species that have been introduced by hobbyists who have dumped their unwanted goldfish into the local waterways. In other instances the hobbyists might have failed to provide an adequate barrier between their goldfish pond and the local waterways.
Don’t ever dump unwanted goldfish into your local waterways. Try giving away your unwanted goldfish to someone that has a goldfish pond or goldfish aquarium. These guys could even live in a koi fish pond if they are big enough in size.