The study looked at how the invasive fish Gambusia affinis grows and eats in different types of habitats in Japan. They found that the fish grew bigger and heavier in still water habitats compared to flowing water habitats. However, the fish were healthier in flowing water habitats. In still water, the fish mainly ate insects, while in flowing water, they ate ants and plants. The fish did not eat tiny animals in flowing water. Overall, the fish had a limited diet in both habitats and had to compete with native fish for food.