Question

In an aquarium two herbivorous species of fish are living together and feeding on phytoplanktons. As per the Gause's Principle, one of the species is to be eliminated in due course of time. but both are surviving well in the aquarium. Give possible reasons.

Answer 1

Gause proposed that when resources are limited then out of the two competing species. one of the species will eventually become extinct. The species with superior predatory skills will survive in the long run. But evidence for such conclusive extinction is rare in nature. Many recent studies do not support Gause's Principle of competitive exclusion. One of the means to survive is called resource partitioning, For example: if two species compete for the same resource; they partition their time of foraging or different foraging patterns. MacArthur showed that five species of Warblers living on the same tree effectively changed their feeding patterns to survive in limited resources.
The same thing can happen in the given aquarium. Either the resources are unlimited or two herbivorous species of fish may have changed their feeding times or feeding pattern to survive in the aquarium.