Shad that spawn in the northern part of the range may survive to spawn again. Spawning begins in the spring as rising water temperatures signal a return to freshwater. Water temperature at the time of upstream migration is typically 56-66 oF. Males arrive at the spawning grounds first, soon followed by the females. A female shad may produce from 100,000 to 600,000 eggs, depending on size, each spawning season. Carried along by the current, the eggs hatch in about four to twelve days, depending on water temperature.
Shad spend their first summer in tributary and river nursery areas.
By autumn, when they are three to five inches long, most juveniles migrate to near-shore coastal wintering areas. Immature shad remain in the ocean before returning to spawn. Males are smaller than females and generally mature earlier. After spawning , adult shad return to the sea and migrate northward to summer feeding grounds in the Gulf of Maine, feeding primarily on zooplankton and small fishes. As water temperatures decline in the fall, particularly October and November, shad migrate southward and offshore.