Answer:
Overfishing is one of the major concern no a days in aquatic systems. overfishing is resulting in the extinction of aquatic organisms and it can lead to several damage to other living organism.
Prawns and small fishes are important organisms in food web or in aquatic system as they maintain the bacterial level or other microorganism level in control.
Prawn and small fishes utilize oxygen and nutrients present in water to survive, if they will get extinct the amount of nutrient and oxygen left will be used by the bacteria and mold living in the system which can have bad impact on human and other organism.
Heron and pelican populations depends on prawn and small fishes for survival as they feed on them and when there will be not sufficient population of prawn and small fishes, there are chances that heron and pelican populations can also get extinct.