The American shad is a species of anadromous fish distributed from southern Labrador to northern Florida. American shad are in family Clupeidae of order Clupeiformes. They are not closely related to the other North American shads. Rather, it seems to form a lineage that diverged from a common ancestor of the European taxa before these diversified.
This is a silvery fish with a single dorsal fin in the middle of the back. There is a large black spot directly behind the top of the gill cover, followed by 4 to 27 spots, which are generally smaller than the first. Sometimes there may be a second row of spots below the first, and more rarely, a third row below the second.
They closely resemble the hickory shad, Alosa mediocris. The most important physical distinction is in the lower jaw. In the American shad this jaw fits easily into a deep notch under the upper jaw, whereas, in the hickory shad the lower jaw protrudes noticeably beyond the upper jaw. Also, the American shad grows cnsiderably larger. Both occur up and down the coasts, but the American shad is predominant in more northerly climates and the hickory shad is predominant in southern climates.
Adult shad weigh between 3 pounds (1.4 kg) and 8 pounds (3.6 kg) and they have a delicate flavor when cooked. It is considered flavorful enough to not require sauces, herbs or spices. It can be boiled, filleted and fried in butter, or baked. Traditionally, a little vinegar is sprinkled over it on the plate. In the eastern United States, roe shad (females) are prized because the eggs are considered a delicacy.
The shad spends most of its life at sea, but swims up fresh rivers to spawn. Northern populations are iteroparous, thus they may survive breeding, return to the sea and then return to freshwaters to spawn several more times. However, southern populations exhibit semelparity, similar to Pacific salmon. In the marine environment, shad are schooling fish. Thousands are often seen at the surface in spring, summer, and autumn. They are hard to find in the winter, as they tend to go deeper before spawning season; they have been pulled up in nets as deep as 65 fathoms (119 m).
Like other herrings, the American Shad is primarily a plankton feeder, but will eat small shrimp and fish eggs. Occasionally they eat small fish, but these are only a minor item in their general diet.
The sexually mature fish enter coastal rivers in spring or early summer, usually when the river water has warmed to 50 to 55 °F (10 to 13 °C). Cooler water appears to interrupt the spawn. Consequently the shad run correspondingly later in the year passing from south to north along the coast, commencing in Georgia in January; in March in the waters tributary to Pamlico and Albemarle Sounds; in April in the Potomac; and in May and June in northern streams generally from Delaware to Canada.
In large rivers, such as the Connecticut, American shad run far upstream. The apparent longest distance is in the St. Johns River of Florida, an extremely slow (1" drop per mile, 1.5 cm per km) river that widens into large lakes; shad have been found 375 miles (600 km) upriver.
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