Trophic significance of microzooplankton to commercially important small pelagic fishes along the southwest coast of India

Microzooplankton is an important component in the plankton food web transferring microbial food web carbon to the higher trophic levels, including fishes. This study investigates the role and significance of microzooplankton in the diet of three economically important small pelagic fishes along the southwest coast of India: Indian oil sardine (Sardinella longiceps), Indian mackerel (Rastrelliger kanagurta) and Commerson's anchovy (Stolephorous commersoni). The diet content of oil sardine was dominated by diatoms throughout the year with an increase in the presence of microzooplankton and copepods during the Northeast Monsoon. Phytoplankton, microzooplankton and copepods represented the diet of Indian mackerel throughout the year. Commerson's anchovy differed considerably in their diet composition from both Indian oil sardine and Indian mackerel as they chiefly depended on a carnivorous diet feeding on copepods, fish eggs, ostracods, lucifers and microzooplankton. The present study concludes that organic carbon from the microbial food web also, through microzooplankton, provides nutritional support to small pelagic fishes along the southwest coast of India but in varying degrees depending on the fish species as well the seasons.

Automated summary

Microzooplankton plays an important role in transferring microbial food web carbon to small pelagic fishes along the southwest coast of India, including Indian oil sardine, Indian mackerel, and Commerson's anchovy. The diet composition varied among the three fish species, with oil sardine mainly feeding on diatoms, Indian mackerel consuming phytoplankton, microzooplankton and copepods, and Commerson's anchovy primarily relying on a carnivorous diet including copepods, fish eggs, ostracods, lucifers, and microzooplankton. The study concludes that microzooplankton provides nutritional support to small pelagic fishes in the region, but the extent varies depending on the fish species and seasons.