The gizzard shad, Dorosoma cepedianum, is a common freshwater fish found across a wide range of habitats in North America. As a member of the herring family, this species is frequently encountered in lakes, reservoirs, rivers, and streams, and can even inhabit brackish waters. Its widespread distribution makes it a familiar sight in aquatic ecosystems throughout the eastern and central United States, and into parts of Canada and Mexico.
General Body Shape and Size
The gizzard shad possesses a deep and compressed body shape, giving it a somewhat flattened appearance from side to side. This body form, typical of the herring family, contributes to its streamlined profile. Along its belly, the gizzard shad features a keel-shaped ridge of sharp-edged, bony scales called scutes, easily felt by rubbing a finger forward along the abdomen.
Adult gizzard shad measure between 8 to 14 inches (20 to 35 cm) in length. While most individuals fall within this range, some have been reported to exceed 20 inches (50 cm). The average length can be larger in northern waters, with 3-year-old fish averaging around 11.2 inches (28.4 cm) and 10-year-old fish around 15.7 inches (39.9 cm).
Distinctive Fins and Mouth
A defining feature of the gizzard shad is its dorsal fin, located on its back, which has a significantly elongated last ray. This ray forms a long, slender, whip-like filament extending far beyond the rest of the fin, serving as a key identifier for the species. This filament is absent in very young fish but begins to grow once the fish reaches about two inches, continuing to develop as it matures.
The gizzard shad’s mouth is small and subterminal, positioned slightly below the tip of its blunt snout. This mouth shape, often an inverted V-shape, is characteristic of species that feed by filtering small particles from the water or grazing on bottom detritus. Unlike many fish, adult gizzard shad do not possess teeth. Other fins include a deeply forked tail fin, which aids in propulsion, and anal fins that have 29 to 35 rays. The pectoral and pelvic fins are also present, with the pelvic fins located in the thoracic or chest region.
Coloration and Other Identifying Marks
The gizzard shad’s body is predominantly silvery, often with a bluish-gray or greenish-gray hue along its back. This darker coloration on the upper body gradually transitions to a plain silvery-white on its sides and belly. Freshly caught individuals might display a greenish or silver tinge overall.
A notable identifying mark is a small, dark, often lustrous purple or black spot located just behind the upper part of the gill cover, also known as the shoulder spot. This spot is more prominent in younger fish and may become faint or even absent in larger adults. The scales are small, thin, and cycloid (smooth-edged), adhering closely to the body, though absent on the head. The fins are dusky in color and lack the prominent yellow tints seen in some similar species.