Planktivore

Planktivores feed on plankton — the drifting community of microscopic and small organisms in the water column. Zooplanktivorous fish (feeding on animal plankton: copepods, krill, larval invertebrates) include herrings, anchovies, sardines, and juvenile fish of many species. Phytoplanktivory (eating plant plankton) is rarer in fish and mostly limited to filterfeeding giants (whale shark, manta ray, basking shark) and larval fish. Planktivorous fish are typically small, abundant, and fast-reproducing — they form a critical mid-trophic link, transforming primary production into biomass available to piscivores.

Atlantic herring feed almost exclusively on copepods (especially Calanus finmarchicus) in the North Atlantic, converting this enormous crustacean biomass into high-energy fish flesh consumed by cod, tuna, whales, seabirds, and humans.