is 12,500 eggs for a two-year-old and peaks at 380,000 eggs for a four-year-old. The eggs are laid in shallow water in clumps, with seemingly no pairing off occurring between individuals. They spawn during the evening and the early hours of the night, and the eggs adhere to underwater vegetation and do not receive any parental attention. Feeding begins three to four days after hatching, and most individuals are 3.3 mm long upon hatching. 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. They are capable of hybridizing with the closely related threadfin shad. Fisheries management 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. They were thought to be easy food for game fish and could help increase the numbers of fish available, as well as decrease the pressures on prey species (such as the bluegill). However, due to their rapid growth, they can quickly grow beyond the size available to many fish. They remain vulnerable to predation by piscivorous birds, such as great blue herons, as well as raccoons and other wetland predators. 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. They can also be harmful exploitative competitors to other species, leading to declines in other fish species' populations. Partly as a result of this, large gizzard shad are sometimes labeled as "nuisances" and "unwanted". 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. Lake management 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 as well as excreting them in more bioavailable forms. 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. Aquatic toxicology Gizzard shad are important to toxicology testing for chemical products. Due