The species is intolerant of cold water temperatures and requires well-oxygenated waters either in rivers or in the sea. Little depth preference is shown. Water velocity is crucial because shad must negotiate river currents and occasional fishways when migrating upstream, and pass safely over spillways when going dowmstream. Spawning runs into rivers at various latitudes on the Pacific and Atlantic coasts of North America peak at water temperatures of 15.5 to 20.0 deg C. American shad have been observed to spawn successfully over silt, mud, sand, gravel, and boulders. Shad spawning areas vary in depth and substrate.
Shad seem to prefer areas dominated by shallow water or broad flats with sand or gravel bottoms.
C caused extensive larval abnormalities. Successful hatches have been reported at salinities ranging from 7.5 ppt at 12.0 oC to 15 ppt at 17 oC. No eggs hatched at a salinity of 22.5 ppt. Sufficient water current velocitites are required to keep the shad eggs suspended in the water column. Minimum age at sexual maturity is 2 years for both males and females. Males become sexually mature when they are 3 to 5 years old and the females mature at 4 to 6 years old.