A study was made to understand the influence of phytoplankton on the abundance of zooplankton, and the relationship between zooplankton and euphausiids in the continental shelf waters of the southwest coast of India. The study revealed that the depth of the water column and nearness to the mainland coupled with the process of upwelling have profound influence on the quantum of production at the primary and secondary levels and the euphausiids available over the shelf area. While the total plankton showed an increase towards the shallower inshore areas, the euphausiids showed an increase in the deep neritic areas thus showing an inverse relationship.