Gizzard Shad

Gizzard shad grow quickly and attain a much larger size than threadfins. Some adults can reach 20 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 20 inches.

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 threadfin shad.

Its 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 (approximately 40° N latitude) along the Atlantic Coast to th`e Gulf of Mexico; and west through the Gulf Coast States to the portions of New Mexico and Colorado east of the Continental Divide.

The Rapid growth of the Gizzard Shad means that largemouth and smallmouth bass 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.

• Habitat

• Life history

• Feeding Habits

• Coloration

• Mouth

• Body

• Biology and Spawning

• Difference between Gizzard Shad and Threadfin Shad.

• Habitat:

  • 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 eutrophication in a lake takes place – that is, as a lake gains fertility through natural aging or added pollutants.

  • 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.

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• Life history:

  • The gizzard shad spawns in spring, May to June, when water temperatures reach the mid-60s to mid-70s.
    
    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, but otherwise show no obvious spawning migration pattern.
    
    Young gizzard shad School in quiet surface waters, bigger adults near bottom.  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

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• Feeding Habits:

  • Gizzard shad are filter feeders straining small organisms particularly from organic deposits. Adults have fine gill rakers to strain these minute plant plankton; the food is ground and digested in their gizzard-like stomach, hence the name.

   

• Coloration:

  • Back silvery blue, somewhat iridescent; sides silvery above, whitish below; abdomen white.
    Fins darkened.
    Dark purplish spot about the size of the eye present immediately behind the upper end of the gill opening.
    Spot becomes obsolete and disappears with age.

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• Mouth:

  • Small sub-terminal, slightly overhung by the rounded snout.
    Centrally notched upper jaw protrudes slightly beyond lower jaw.
    Upper jaw reaching below the front margin of the eye. Gill rakers long, slender

   

• Body:

  • Deep strongly compressed laterally.
    Average length 8.5 -13.5 in.
    Scales large, thin, rounded and smooth-edged , Falling off or shed at a specific season or stage of growth.
    Lateral line lacking.
    Median lateral series of scales 61 (52-70).
    Ridge of sawlike  scales close to the abdomen.

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• Gizzard Shad differ from Threadfin Shad by:

  • lower jaw shorter than upper jaw;
    a much shorter dorsal fin filament;
    absence of black pigment on the chin and floor of mouth; more than 17 midventral scutes in the prepelvic series;
    more scales in the lateral series; more anal fin rays.
     

• Biology and Spawning:

  • Spring when water temperatures reach the 60s, the gizzard shad spawn begins at night in shallow water.

  • As early as age two they gather in large schools to broadcast their eggs and milt in shoreline shallows.

  • Females produce up to 400,000 eggs that adhere to plant and rock substrate, the eggs hatching in two to three days.

  • No nesting behavior or parental care is shown by adults.

  • Growth is rapid – up to seven inches in the first year have been recorded.

  • Will school up as juveniles in quiet surface waters, adults near bottom.

  • Spawn at night in spring, in shallows.

  • Eggs randomly scattered adhere to plants, rocks or firm substrate.

  • Preferred Temps 66 -72 degrees F.  Will start at 50 degrees

  • Six week spawning period.

  • Most spawn at age 2. producing  22,000 to 400,000 eggs .

  • Incubation 2-4 days.

  • Buoyant larvae become plankton.

  • Life span 3 -11 years, few live beyond age 3. In general, short life spans are correlated with rapid growth rates in the first year of life. In more northern parts of its range, gizzard shad typically live to ages 5 to 7 and may live to ages 10 or 11 (Miller 1960; Jester 1962).

  • Adult die-offs common.

  • Adults bottom filter feeding from areas along shorelines.

  • Open water fish have mostly phytoplankton and sand for digestion.

  • Juveniles planktivorous.

  • Preferred temp is 72 -76 degrees F.

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Shad BIOLOGICAL REPORT 82(10.112

2009 Study University of Florida

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