Living Environment Regents Practice Test

What impact do spiny water fleas have on native fish populations?

1. They enhance the growth of zooplankton

2. They feed on important food sources for native fishes

3. They have no impact on the ecosystem

4. They increase the population of native fishes

The correct answer is: They feed on important food sources for native fishes

Spiny water fleas have a significant negative impact on native fish populations primarily because they feed on small zooplankton, which are essential food sources for many native fish species. These invasive organisms are efficient predators that can outcompete native zooplankton for resources, leading to a decline in the availability of these crucial food items. As a result, native fish populations may experience decreased growth rates and reproductive success due to malnutrition or lack of adequate food. In ecosystems where spiny water fleas have been introduced, the reduction in zooplankton can disrupt the entire food web, impacting not only fish but also other organisms that rely on zooplankton as a food source. This cascading effect emphasizes their role as a harmful invasive species that contributes to ecosystem imbalance and the decline of native fish.