Why do most commercially important clupeiform fishes feed on plankton?

All of the most abundant and economically important species of clupeiform fishes are plankton feeders. Their commercial value is directly linked to their feeding habits and the intensity of their movements.1

While some clupeiforms are predatory, these species are relatively scarce and generally possess much lower commercial value than their plankton-feeding counterparts. For example, the plankton-feeding race of the Russian shad is significantly more abundant and frequently caught than the fish-eating race of the same species.1

The high abundance of these plankton-feeding fishes is a primary factor in their status as the most heavily exploited of all fish groups, with approximately 20 species providing more than one-third of the world's total fish catch. This success is further supported by factors such as the size of their inhabited areas and, in some cases, early sexual maturity.21