Beneficial effects

•  Zooplankton   play  a pivotal role in the aquatic food chain and by forming an intermediate link , they transfer the energy to the higher trophic levels  as   they  graze on  phytoplankton.  Most of the zooplankton  form a very good food source for the larvae and adult  of commercially important marine fishes.   It is worth mentioning here that the abundance of jelly fishes in the sea is considered as a menace or hindrance to the fishing operations as they are known to clog the fish nets. Apart from this, areas rich in jelly fishes are also invariably observed to be devoid of fishes and that way they serve as the indicator of poor fisheries..

• The presence of rich shoal of herrings   and mackerels is indicated by the abundance of copepod species Calanus. The abundance of krill (Euphausia superba)  indicates  the presence of baleen whales to the whalers (those who catch whales)

Harmful effects

•  Some zooplankton are also known to have some adverse effects on the fishery as they are the voracious predators on the fish eggs and larvae, which may lead to  poor fishery of that location. E.g., Sagitta sp. (arrow worm) .