Gizzard shad grow quickly and attain a much larger
size than threadfins.
Some adults can reach 18 inches long and weigh over 2-pounds.
The gizzard shad has the typical herring family shape, but with a
distinctive dorsal fin. Its short, soft-rayed dorsal fin is located
at the center of its back. It has a long, trailing filament as the
rear ray, longer than any of the other rays. The gizzard shad's back
is silvery blue-green to gray. The sides are silvery or reflect
blue, green, brassy or reddish tints. There is no lateral line. The
tail is deeply forked, and the lower jaw is slightly shorter than
the upper jaw. The snout is blunt. The mouth is small, and there is
a deep notch in the center of the upper jaw. The gizzard shad's eye
is large. There is a big, purplish-blue spot near the edge of the
upper gill in young gizzard shad and small adults. This spot is
faint or disappears completely in larger, older fish. The fins are
dusky and there are the usual herring sawtooth-edged belly scales.
Gizzard shad grow rapidly and can reach a maximum size of about 18
Gizzard shad are omnivorous filter feeder taking both phytoplankton
and zoo plankton. The adults have more than 400, fine gill rakers that can catch minute plankton.
Gizzard Shad have an unusual digestion process for fish. The
vegetable material they eat is ground in a gizzard like stomach.
Some bottom material is often ingested while feeding.
Lake and reservoir populations use both
the littoral and limnetic zones . The gizzard shad is essentially an open water
species, living at or near the surface, however, they have been collected at depths of
up to 100 feet.
They will hybridize with the
The Rapid growth of the Gizzard Shad means that largemouth and
are able to eat them for only a short time each spring. Over populations
occur if not controlled.
The Gizzard Shad spends most of its time in large schools cruising for food.
The gizzard shad is a schooling fish found in lakes and
impoundments. It also lives in the backwaters of sluggish rivers and the
deep, slow pools of smaller streams.
Gizzard shad become more abundant as a lake gains fertility through natural aging or
Generally found in fresh water, gizzard shad can also live in the brackish
water of tidal zones and estuaries.
Unlike many other herrings, gizzard shad
are nonmigratory and stay near their home areas.
They are often found over a
mucky bottom, which they filter when feeding.
Range extends from southeastern South Dakota and central
Minnesota, throughout the Mississippi and Great Lakes drainages to about
as far north as the St. Lawrence River, near Quebec; from southern New
York along the Atlantic Coast to the Gulf of Mexico; and west through
the Gulf Coast States to the portions of New Mexico and Colorado.
gizzard shad spawns
in spring, May to June, when water temperatures reach the mid-60s to
Striped bass are the dominant predator for the large Gizzards and keep
them under control so that young Largemouth bass and Large shad don't have
to compete for the same limited planktonic food allowing the fingerling black bass to grow quicker.
Gizzard shad move upstream into shallower waters to spawn,
show no obvious spawning migration pattern.
Young gizzard shad School in quiet surface waters, bigger adults near
Six week spawning period. Most spawn at age 2.
Buoyant larvae become plankton. Life span 4-6 years, few live beyond age 3.
Spawning Habits of Gizzard Shad
Williamson, K. L., and P. C. Nelson. 1985
Gizzard Shad Habitat suitability index models and instream flow suitability