Species Profile – Gizzard Shad

Wed, April 26, 2017 | Lakes and Parks

Scientific Name:               Dorosoma cepedianum

Common Name(s):         Gizzard Shad, Shad

 

Identification:                                                                          

The gizzard shad, Dorosoma cepedianum, is commonly mistaken for the similar threadfin shad, Dorosoma petenense.  They can be easily distinguished by the overhanging upper jaw in the gizzard shad, and by the absence of yellow coloration in the gizzard shad’s fins.  Adult gizzard shad in Arkansas usually range from 12-16 inches and weigh less than one pound.  Maximum size is around 20 inches and 3.5 lbs., with the current state record at 2 lbs. 14 oz. from the White River.  The gizzard shad has a thin, compressed, oblong body with a silvery-green coloration on the back, fading to plain silver on the belly.  The fin on the back of the fish has a long, thin filament sticking out past the rest of the fin.  The tail fin is deeply forked.  It has a large dark spot on the shoulder and the fins are grayish in color.

 

 

 

Range:

The gizzard shad is native to most of the Mississippi River drainage and the eastern United States.  They occur in many different habitats including lakes, rivers, streams, and clear or turbid waters.  Gizzard shad can be found in strong currents, but they favor calm deeper water.

Ecology:

The Gizzard Shad is one of Arkansas’ most adaptable species, occurring in a diversity of habitats; however, they do not cope well with sudden temperature changes or low oxygen levels.  Young shad are excellent food for predatory fish, but adults are often too big to be utilized as food.

In Arkansas, spawning occurs in April through May.  Most spawning occurs at night near the surface, usually in shallower water.  Females and males swim together in a school and release eggs and sperm.  They have adhesive eggs that sink to the bottom and become attached to whatever substrate they touch.  Adults do not take care of the eggs or young.  Eggs tend to hatch faster in warmer water.

The gizzard shad is a forager, consuming plankton and particulate matter they filter from the water by their gills. They can also graze over the bottom consuming aquatic insects and detritus.

Gizzard shad have negative impacts on ecosystems where they compete for food with different species.  They also have been known to increase phytoplankton levels, consequently increasing turbidity and impacting visual predators.  Since gizzard shad are quick to overpopulate and can grow rapidly, some management techniques have been used to help control populations like the stocking of larger predatory species such as striped bass.  Late winter shad kills are common due to low temperatures and starvation.

 

Special Notes:

Here in Bella Vista, gizzard shad have not been stocked in any of the lakes.  Their presence is the result of well intentioned, but uninformed anglers.  Deleterious effects far outweigh any of the benefits they bring.  “Because of its direct use of phytoplankton and high reproductive capacity, the gizzard shad has been a prime candidate for introduction to waters which lack a major forage base for gamefishes.  However, due to their rapid growth, gizzard shad are available to most predators for only a short time, thus they are less esteemed as forage than are threadfin shad” (Jenkins and Burkhead1993).  We have an abundance of large individuals that actively filter off plankton making it unusable to young gamefish that require it.  In addition competition for resources has left these large adults in poor condition and as a result nonreproductive.  Result: many large adults and few consumable young.  Threadfin shad only survive about 50% of our winters, so long term establishment is impossible.  Better species are the bluegill which spawn up to 5 times per year and the brook silversides which are numerous in Bella Vista Lakes.  Our stepped up fertilization regime will help stimulate the shad to spawn, but it would be better if they weren’t present.  They are found in all lakes and their populations are maintained naturally.  As bait, they are mainly used dead, because they often die quickly after being handled. They like deep, open water so they can easily be caught with gill nets. Many fisherman use them as bait for trotlines.

Citation:

Jenkins, R. E., and N. M. Burkhead.  1993.  Freshwater fishes of Virginia.  American Fisheries Society, Bethesda, Maryland.