Gizzard shad (Dorsoma cepedianum) also are a member of the herring family - Clupeidae.
They occur in many rivers and reservoirs across the southeast and are occasionally stocked in ponds managed for trophy largemouth bass. When it comes to gizzard shad vs threadfin shad, there are some size differences. Adult gizzard shad are substantially larger than threadfin shad, often reaching lengths in excess of 12 inches in fertile waters. Juvenile gizzard shad can resemble threadfin shad in coloration. However, gizzard shad have a subterminal mouth with the upper jaw extending well past the lower jaw. Also, the upper jaw has a well-defined notch in the center. Gizzard shad are pelagic filter feeders, feeding primarily on plankton, algae, and suspended organic material. However, they will often "graze" on the bottom, feeding on aquatic insects and organic sediment. Gizzard shad begin spawning about the same time as threadfin shad; however, reproduction during the latter part of the growing season is less evident. Also, gizzard shad are much more tolerant of low temperature than threadfin shad and not as susceptible to winter mortality.
Gizzard Shad in Sport Fish Ponds
In certain situations, and if managed correctly, gizzard shad can be an ideal supplemental forage for producing exceptionally large bass. Trophy bass require large food items, measuring 6 to 10 inches in length to continue to grow. Gizzard shad quickly grow to 6 and 7 inches long and will achieve a larger adult size than threadfin shad, thus providing the larger bass with a more efficient prey item. They may also serve as an alternative to threadfin shad as an additional forage base in ponds located in colder climates.
Drawbacks
When stocked into a bass/bluegill pond, their large potential size and rapid growth rate often allow gizzard shad to "stockpile" at a size too large to be consumed by the bass. Over time, they can occupy a large portion of the total fish biomass within the pond. Gizzard shad reproduction eventually will decrease in response to over-crowding, resulting in little forage for the average size bass in the population. To avoid this situation, it is usually necessary to remove a portion of the gizzard shad population every 3 to 5 years with rotenone. Maintaining a healthy, reproducing population is the key to managing gizzard shad in sport fish ponds.
The requirements of gizzard shad in ponds are similar to threadfin shad.
However, gizzard shad have a much broader range of water temperature and water quality in which they can live. Introducing gizzard shad with threadfin shad creates a more natural environment for each species by providing a healthy competition for the available food. We have found that the period gizzard shad continue reproducing is often extended in ponds that also have an established threadfin shad population. Therefore, the amount of time between corrective rotenone treatments can be extended. When stocked together, threadfin shad will be especially beneficial to the growth of smaller bass. We recommend stocking gizzard shad in trophy bass ponds when they have a large number of bass over 16 inches in length in the population. They are usually stocked in the spring but can be stocked later in the growing season when available. The stocking rate may be similar to threadfin shad; however, it is usually determined individually for each pond.