How does piranhas spread to the world?

Piranhas are native to the freshwater rivers and lakes of South America, particularly in the Amazon Basin. They have spread to other regions primarily through human activities, such as aquarium trade and the unintentional release of pets into non-native environments. Additionally, they have been introduced to various water bodies for sport fishing or as part of ecosystem management, leading to their establishment in places outside their original habitat. This spread has raised concerns about their impact on local ecosystems and fish populations.