Evolution would be the answer you may be looking for.
Peptidoglycan is the answer
Invasive species are successful in novel environment due to lack of natural predator or competition. Therefore if the non-native share a niche with other fish in the lake ecosystem, there will definitely be competition for resources. This could lead to competitive exclusion of one species or resource partitioning between the species consequently, the non-native fish species will not invade the new environment unchecked. I hope this helps
