The fish in the ocean are an example of "common resource".
Explanation:
Fish in the Ocean is the common resource for aquatic animals like small fish is consumed by the larger fish. Fishes are also very popular as sea food for human beings being a highly protein and fat rich food. Thus its a common resource for both humans and other animals.
Like fish their are many other common resources like prawn, crab, etc but consuming them in excessive manner direct their population counts towards declination. Thus an equilibrium is needed to be maintained for such resources to prevent a scarcity and maintain ecosystem.
