These fish produce low hatch-rates, low survival, but still strong enough to be significant. Gizzard shad are hearty in most climates, even ice cover, as long as oxygen is plentiful. If you don't have enough large bass to eat fast growing shad, these silver- sided creatures can grow too big, too fast to accommodate average size bass. If you feed your fish with a high-protein supplement, watch for gizzards to gather in schools and chow down on the small pellets. Unfortunately, they may out compete your bluegill.
Threadfins are different.
A seven-incher is huge, but watch them die when water temperatures fall below 42 degrees. But, these high-RPM fish are love machines. Spawning continually through warm months, threadfin shad have the equipment and metabolism rate to reproduce exponentially. They stick eggs on underwater grass, each shad spawning every 40-60 days, depending on temperature. Baby shad mature and spawn at 60 days of age.