Aspecies of fish is introduced into a lake the fish is better at hunting for food than the old fish. the old fish die off, the new fish population increases. which is the best way to describe these fish in the new ecosystem

Invasive species.

Explanation:

An invasive specie can be defined as the species that is not native to a particular place and is introduced to a different place intentionally or non intentionally.

This species on a different place perfectly suits into the environment there and replaces the native species already living there by hunting of the food in a better way.

is this a psat question, if so do not cheat try your best.