Gambusia affinis, an elchojista fish, lives in the rivers of the United States (USA) and Mexico. However, it is interned in the rivers of the US, Canada, the former Soviet Union, New Zealand and Australia to compose mosquito larvae that contaminate malaria. In the new rivers this fish ingests to taste not only mosquitoes but also tadpoles of frogs and other amphibians.
According to Lee Kats, tadpoles cannot defend themselves from foreign predators. This is one of the three main causes of the disappearance of amphibians.