Invasive species pose a serious threat to native species and their habitat, in addition to serious economic damages. Therefore, it is critical to study the potential impacts of invasive species to native species and their habitats before or in an early stage of invasion. This helps to mitigate the damage and come up with effective management strategies. We study biological interactions between native and non-native aquatic species focusing on crayfish. We conduct experiments with laboratory microcosms and field mesocosms to explore impacts of reciprocal competition and predation on population dynamics, in addition to field observations.