[11] Gizzard shad are planktivorous in early life, feeding mainly on phytoplankton and zooplankton, such as periphyton, chrysophyta and rotifera, as larvae.

[12] Consumptive demand of young of year fish (including larvae) can be intense enough to cause collapses in the zooplankton community, which has far-reaching effects through the ecosystem of which they are a part.

[5] In midwestern USA reservoirs, where gizzard shad are often the most abundant fish (by biomass), they usually switch to diets dominated by sediment detritus during the first year of life,[13] whereas in some natural lakes they may rely heavily on zooplankton throughout their lives.

[5] They have been observed at night in Lake Mead, Arizona congregating in schools in very shallow water two to three feet deep during the fall.

[citation needed] The start of the spawning period is typically between mid-May and early June, and is triggered by rising water temperatures.

[8] Gizzard shad have very high fecundity and a rapid growth rate, meaning they can become a large part of an ecosystem, in terms of abundance and biomass, very quickly.

[2] Gizzard shad were introduced into many lake and river systems as a source of food for game fish, such as walleye, bass, and trout, because of their small size and relatively high abundance.

[18] In addition, gizzard shad spawn in large numbers and can reach densities high enough to ensure that many of them survive past the first year, making them essentially invulnerable to fish predation.

[20] However, gizzard shad can help to control populations of zooplankton and insect larvae in productive ecosystems through their unique capabilities as predators of small organisms.

[18] Gizzard shad can increase productivity in an ecosystem through redistribution of nutrients, particularly in their adult stages when they consume detritus in lower depths of the lake and both make them available to other predator species[15] as well as excreting them in more bioavailable forms.

[21] Because of this, gizzard shad can have a strong effect on algal production even when phosphorus loading from watersheds is high, and can counteract management efforts to combat cultural eutrophication.

Due to the food web dependencies and fecundity gizzard shad are somewhat the water bound version of "canary in the coal mine.