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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: Gizzard Shad

Synonyms and Other Names: American Gizzard shad, Hickory Shad, Eastern Gizzard shad, Mud Shad, Skipjack 

Taxonomy: available through www.itis.gov

Identification: Gizzard shad (Dorosoma cepedianum) is a fish within the herring family that is native to fresh and brackish waters. It is characterized by the blunt snout, small toothless mouth, a long trailing last dorsal ray, and closely packed gill rakers which can be present in numbers beyond 400. Eyes have “eyelids” composed of fat-storing adipose tissue. The gill membranes are free from the throat. The body is short and deep and ranges from moderately to strongly compressed. The abdomen compresses to a ridge lined with bony scales called scutes. Scales are thin, cycloid (circular, smooth-edged outer margin and uniform) and largely adherent to the body. Scales are not found on the head and may be present on the back between the dorsal fin and back of the skull (Miller 1960; Etnier and Starnes 1993).

Gizzard shad may be confused with Threadfin Shad (Dorosoma pentenense). See Table for differentiating characteristics.

Gizzard shad (D. cepedianum)	Threadfin Shad (D. petenense)
Snout blunt	Snout pointed
Subterminal mounted lower jaw	Projecting lower jaw
No black specks on chin and floor of mouth	Black specks on chin and floor of mouth
Fin color dusky	Fin color yellow
52-70 lateral scales	40-48 lateral scales

Page and Burr 2011

Size: 52 cm.

Native Range: Native in the Mississippi, Atlantic, and Gulf Slope drainages from Quebec to central North Dakota and New Mexico, and south to central Florida and Mexico (Page and Burr 1991). It is unclear whether Gizzard shad are native to the southern Great Lakes or gained access through canals and rivers.

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Native range data for this species provided in part by NatureServe

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Gizzard shad are primarily found in large rivers, reservoirs, lakes, swamps, and other freshwater environments with turbidity ranging from clear to silty. Its preference is quieter open waters although it can be commonly found in the strong current of the upper Mississippi River (Miller 1960). Adults can also be found in brackish and saline waters of estuaries and bays (Whitehead 1985). Optimal habitat for the species is warm, fertile, shallow bodies of water with soft mud bottoms, low predator abundance and high turbidity. Lacustrine habitats with optimal conditions are prone to overpopulation by Gizzard shad. Moderate to heavy predation, changing water levels, deep clear water, and steep shorelines tend to lead to lower Gizzard shad populations (Williamson and Nelson 1985). Temperature plays a large role in population size. Individuals are most frequently found in areas ranging from 22-29°C with satisfactory growth observed at temperatures up to 34°C (Williamson and Nelson 1985). Populations appear to fluctuate in response to low temperatures and die-offs are common in the winter at higher latitudes (Etnier and Starnes 1993; Becker 1983). However, Gizzard shad may survive severe winters in areas where water temperatures are uncharacteristically warm, such as near an industrial warm-water discharge. The spread of this species in Lake Michigan is thought to be connected to artificial warm spots in harbors and industrial bays (Becker 1983). Individuals avoid waters with low dissolved oxygen and are normally absent from water with less than 2 mg/L of dissolved oxygen (Williamson and Nelson 1985).
Gizzard shad are planktivores, straining minute organic particles with their gill rakers into their pharyngeal organ which is thought to concentrate and process food for swallowing. They also feed heavily on detritus found on bottom sediments, individuals consume an average of 13% of their wet weight biomass in dry sediment each day. Their diet remains largely similar at different sizes and has been found to contain algae, phytoplankton, zooplankton, and plant debris. Because Gizzard shad are primary consumers, extremely large populations can be supported. Fry feed primarily on copepods and cladocerans, whereas adults consume large amounts of phytoplankton and zooplankton. Gizzard shad is part of the diet of at least 17 game fishes some of which include Walleyes, White Bass, Largemouth Bass, White Crappie, Gars, Black Crappie, Sauger, Yellow Trout, Catfish, Freshwater Drum, and Lake Trout. The Striped Bass and Muskellunge have been introduced into reservoirs to prey on Gizzard shad.  Waterfowl also prey on the species. Winter die-offs cause individuals to float to the surface where they are consumed by crows, turkey vultures, bald eagles, and waterfowl. Gizzard shad grow rapidly in shallow, fertile impediments with abundant food and long growing seasons. This rapid growth frequently causes individuals to become too large for most predators, reaching 10-18 cm within the first year (Etnier and Starnes 1993; Williamson and Nelson 1985; Miller 1960; Mundahl 1990).
Spawning of Gizzard shad occurs from mid-May to mid-June near the surface of water in low-gradient areas. Adult females and males gather in large aggregations and eject sperm and eggs into the water. Eggs sink to the bottom and adhere to any object or surface they come in contact with. The average female produces approximately 300,000 eggs per year, eggs will hatch in 2-3 days. Young fish travel in compact schools after hatching and will typically disperse by fall, schooling is rare at age one. Reproductive maturity is normally reached at ages 2 or 3. Lifespan depends on the environment a population is found in and shorter life spans are associated with rapid growth in the first year of life. Longer life spans are typical in the northern parts of its range and individuals live to 5-7 years and have been reported living up to 10-11 years (Etnier and Starnes 1993; Williamson and Nelson 1985; Miller 1960).

Means of Introduction: These fish were stocked intentionally for forage. The Wyoming populations also spread from introductions into Nebraska (Baxter and Simon 1970). In Pennsylvania, Gizzard shad were stocked accidentally with American shad (Denoncourt et al. 1975). In Vermont, they have expanded their range through the Connecticut River assisted by fishways that were constructed for American Shad Alosa sapidissima and Atlantic Salmon (Salmo salar) restoration (Ken Cox, personal communication). They likely gained access to Lake Champlain through the Hudson Barge Canal that links the lake to the Hudson River (Ken Cox, personal communication). They gained access to Lake Michigan through either the Chicago River Canal or the Fox-Wisconsin Canal (Becker 1983), and to Lake Erie through the Ohio Canal (Jordan 1882).
Gizzard shad gained access into the Colorado River in 2000 after some escaped Morgan Lake in NW New Mexico, where they were accidentally stocked with largemouth bass (Knowles 2002).  By early 2008, they were found as far downstream as the Grand Canyon in Arizona.

Status: Established in many states.  Cryptogenic (unsure if native or nonnative) in the southern Great Lakes (Ontario, Lake St. Clair, southern Lake Erie, southern Lake Michigan) with range expansions northward.  Widespread, with populations now reported in all 5 Great Lakes and Lake St. Clair as well as numerous inland Lakes in the basin.

Impact of Introduction: Competition for food between gizzard shad and other fish species may occur (Burns 1966; Moyle 1976). Jenkins (1994) found that gizzard shad directly compete with centrarchids resulting in decreased growth and size of the centrarchids. Aday et al. (2003) foud that gizzard shad caused reduced growth rates and maximum size in bluegill. In addition, Aday et al. (2003) found that gizzard shad can significantly increase phytoplankton levels, subsequently increasing turbidity and potentially impacting visual predators. Gizzard shad show tremendous invasion potential. After only two plantings totally 1020 fish in Lake Havasu, the species spread through the Colorado River from Davis Dam southward to the Mexican border, the Salton Sea, and associated irrigation ditches within only 18 months (Burns 1966).

Remarks: The gizzard shad has expanded its range naturally since the 1600s to include Massachusetts (O'Leary and Smith 1987; Hartel 1992). Jordan (1882) stated that the gizzard shad was not found in Lake Erie prior to completion of the Ohio Canal. Cold weather limits this species' northern range (Becker 1983). Propst and Carlson (1986) believe the gizzard shad may be native to the South Platte drainage in Colorado.

References: (click for full references)

Aday, D.D., R.J.H. Hoxmeier, and D.H. Wahl. 2003. Direct and indirect effects of gizzard shad on bluegill growth and population size structure. Transactions of the American Fisheries Society 132:47-56.

Baxter, G. T., and J. R. Simon. 1970. Wyoming fishes. Wyoming Game and Fish Department Bulletin 4, Cheyenne, WY. 168 pp.

Becker, G.C. 1983. Fishes of Wisconsin. University of Wisconsin Press, Madison, WI. http://digital.library.wisc.edu/1711.dl/EcoNatRes.FishesWI.

Beckman, W. C. 1952. Guide to the fishes of Colorado. University of Colorado Museum, Boulder, CO.

Bennett, G.W. 1943. Management of small artificial lakes: a summary of fisheries investigations, 1938-1942. Bulletin of the Illinois Natural History Survey 22:357-376.

Bouc, K. 1987. The fish book. Nebraskaland Magazine 65(1):1-130.

Burns, J.W. 1966. Threadfin shad. Pages 481-488 in Calhoun, A, ed. Inland fisheries management. California Department of Fish and Game. Sacramento, CA.

Burr, B. M., and M. L. Warren, Jr. 1986. A distributional atlas of Kentucky fishes. Kentucky Nature Preserves Commission Scientific and Technical Series 4. 398 pp.

Catalano, M., J.R. Dotson, L. De Brabandere, M.S. Allen, and T.K. Frazer. 2007. Biomanipulation impacts on Gizzard Shad population dynamics, lake water quality, and a recreational fishery. St. Johns River Water Management District, Palatka, FL.

Cooper, E.L. 1983. Fishes of Pennsylvania and the Northeastern United States. Pennsylvania State University Press University Park, PA.

Cox, K. - Vermont Department of Fish and Wildlife, North Springfield, VT.

Cross, F.B. 1967. Handbook of Fishes of Kansas. State Biological Survey and University of Kansas Museum of Natural History, Miscellaneous Publication 45, Topeka, KS.

Denoncourt, R F., T.B. Robbins, and R. Hesser. 1975. Recent introductions and reintroductions to the Pennsylvania fish fauna of the Susquehanna River drainage above Conowingo Dam. Proceedings of the Pennsylvania Academy of Science 49:57-58.

Etnier, D.A., and W.C. Starnes. 1993. The fishes of Tennessee. The University of Tennessee Press, Knoxville, TN.

Hartel, K. E. 1992. Non-native fishes known from Massachusetts freshwaters. Occasional Reports of the Museum of Comparative Zoology, Harvard University, Fish Department, Cambridge, MA. 2. September. pp. 1-9.

Hubert, W. 1994. Exotic fish. Pages 158-174 in T. L. Parrish, and S. H. Anderson, editors. Exotic species manual. Wyoming Game and Fish Department, Laramie, WY.

Jenkins, R. E., and N. M. Burkhead. 1994. Freshwater fishes of Virginia. American Fisheries Society, Bethesda, MD.

Jordan, D.S. 1882. Report on the fishes of Ohio. Report of the Geological Survey of Ohio 4(1):735-1002.

Knowles, S. 2002. Fish and Wildlife blunders in Lake Powell. Salt Lake Tribune. 2002(27 August).

Lee, D.S., C.R. Gilbert, C.H. Hocutt, R.E. Jenkins, D.E. McAllister, and J.R. Stauffer, Jr. 1980. Atlas of North American Freshwater Fishes. North Carolina State Museum of Natural History, Raleigh, NC.

Miller, R.R. 1957. Origin and dispersal of the alewife, Alosa pseudoharengus, and the gizzard shad, Dorosoma cepedianum, in the Great Lakes. Transactions of the American Fisheries Society 86:97-111.

Miller, R.R. 1960. Systematics and biology of the Gizzard Shad (Dorosoma cepedianum) and related fishes. U.S. Fish and Wildlife Service, Washington, D.C.

Minckley, W.L., and L.A. Krumholz. 1960. Natural hybridization between the clupeid genera Dorosoma and Signalosa, with a report on the distribution of S. petenensis. Zoologica 44(4):171-180.

Moyle, P.B. 1976. Inland fishes of California. University of California Press Berkeley, CA.

Mundahl, N.D. 1990. Sediment processing by gizzard shad, Dorosoma cepedianum (Lesueur), in Acton Lake, Ohio, U.S.A. Journal of Fish Biology 38:565-572.

O'Leary, J., and D. G. Smith. 1987. Occurrence of the first migration of the gizzard shad, (Dorosoma cepedianum), in the Connecticut River, Massachussetts. U.S. National Marine Service Fishery Bulletin 85(2):380-383.

Page, L.M., and B.M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. The Peterson Field Guide Series, volume 42. Houghton Mifflin Company, Boston, MA.

Page, L.M., and B.M. Burr. 2011. Peterson field guide to freshwater fishes of North America north of Mexico. 2nd edition. Houghton Mifflin Harcourt, Boston, MA.

Propst, D.L., and C.A. Carlson. 1986. The distribution and status of warmwater fishes in the Platte River drainage, Colorado. Southwestern Naturalist 31(2):149-167.

Schmidt, B. - Chief Fisheries Mangement, Division of Wildlife Resources, Salt Lake City, UT. Response to NBS-G non-indigenous questionaire. 1992.

Smith, C. L. 1985. The inland fishes of New York state. New York State Department of Environmental Conservation, Albany, NY. 522 pp.

Smith, P. W. 1979. The fishes of Illinois. University of Illinois Press, Urbana, IL.

Welker, M.T., C.L. Pierce, and D.H. Wahl. 1994. Growth and survival of larval fishes: roles of competition and zooplankton abundance. Transactions of the American Fisheries Society 123:703-717. https://onlinelibrary.wiley.com/doi/abs/10.1577/1548-8659%281994%29123%3C0703%3AGASOLF%3E2.3.CO%3B2.

Whitehead, J.P. 1985. FAO Species Catalogue. Vol. 7. Clupeoid Fishes of the World (Suborder Clupeoidei). An annotated and illustrated catalogue of the herrings, sardines, pilchards, sprats, anchovies and wolf-herrings. Part 1 - Chirocentridae, Clupeidae and Pristigasteridae. Volume FAO Fisheries Synopsis No. 125, Vol. 7. Food and Agriculture Organization of the United Nations.

Wibur, J. - Bureau of Reclamation, Albuquerque, NM.

Williamson, K.L. and P.C. Nelson. 1985. Habitat Suitability Index Models and Instream Flow Suitability Curves: Gizzard Shad. U.S. Fish and Wildlife Service, Fort Collins, CO.

Woodling, J. 1985. Colorado's little fish: a guide to the minnows and other lesser known fishes in the state of Colorado. Colorado Division of Wildlife, Denver, CO. 77 pp.

Wynne, F. 2013. Removal of undesirable fishes from warmwater ponds. Kentucky State University Cooperative Extension Program, Mayfield, KY.

Other Resources:
Distribution in Illinois - ILNHS

FishBase Fact Sheet

Great Lakes Waterlife

Author: Fuller, P., Neilson, M.E., Hopper, K. and Sturtevant, R.

Peer Review Date: 4/12/2013

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.