American shad

The shad spends most of its life in the Atlantic Ocean, but swims up freshwater rivers to spawn.[4] Northern populations are iteroparous, thus they may survive breeding, return to the sea, and then return to fresh waters 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 in the range 13–18 °C (55–64 °F);[9] they have been pulled up in nets as deep as 120 metres (65 fathoms).

Like other herrings, the American shad is primarily a plankton feeder, but eats small shrimp and fish eggs. Occasionally they eat small fish, but these are only a minor item in their general diet.[2]

The sexually mature American shad enter coastal rivers in spring or early summer, usually when the river water has warmed to 10 to 13 °C (50 to 55 °F). 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.[2]

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 (drops 1 in per mile, 1.5 cm per km) river that widens into large lakes; shad have been found 600 km (375 mi) upriver.[2]

The spawning fish select sandy or pebbly shallows and deposit their eggs primarily between sundown and midnight. Females release eggs in batches of about 30,000 eggs, though an estimated as many as 156,000 eggs are deposited by very large fish. Total annual egg production is 200,000–600,000 eggs per female with larger fish producing more. In rivers north of Cape Fear, the spent fish, now very emaciated, return to the sea immediately after spawning. In southern rivers, most shad die after spawning.

The eggs are transparent, pale pink, or amber, and being semibuoyant and not sticky like those of other herrings, they roll about on the bottom with the current. The eggs hatch in 12 to 15 days at 11 °C (52 °F), in six to eight days at 17 °C (63 °F), which covers the range characteristic of Maine and Bay of Fundy rivers during the season of incubation.

The fry are about 9 to 10 mm (11⁄32 to 13⁄32 in) long. Juvenile shad remain in the rivers until fall, when they move down to salt water; they are now 40 to 115 mm (1+1⁄2 to 4+1⁄2 in) long, resembling their parents in appearance.

As adults, shad filter feed at sea and during their return journey to spawn. They are pursued and hunted primarily by striped bass, and at times, harbor seals. They may not actively feed on their return, and are caught with special 'dart' lures instead of typical bait.

Harbor seal in freshwater Connecticut River, following the shad run

Like most herring species, American shad are very high in omega 3 fatty acids, and in particular contain nearly twice as much per unit weight as wild salmon. They are also very low in toxins such as PCBs, dioxins, and mercury by EPA estimates. The American or Atlantic shad (A. sapidissima) is a valued food fish.

An American shad is measured during a survey at the Holyoke Dam fish ladder, circa 1970

Declines in the Atlantic coast shad population were documented as early as the turn of the 20th century. Traditionally, shad were caught along with salmon in set nets, which were suspended from poles driven into the river bed reasonably close to shore in tidal water.[7] Many of the rivers where shad were once common now suffer from pollution; however, the short time spent by shad in fresh water may minimize contamination. For example, fisheries scientists have found that shad in the Hudson River are not in the river long enough to be affected by PCBs and other contaminants (however, fishing for or possessing American shad [including catch and release] in the Hudson River or Marine District is now prohibited).[10][11] Pollution, however, may impact shad reproduction and studies have been undertaken to determine whether fingerlings suffer DNA damage.

Most of the rivers across the historic range of shad are now heavily dammed, eliminating many of the spawning grounds. For example, the number of shad harvested in the Merrimack River declined from almost 900,000 in 1789 to none in 1888, likely due to the inability to reach their spawning ground following a period of heavy dam construction. Since then, fish passage efforts have begun to remedy this situation, including the Chesapeake Bay program.[4] While recreational angling has almost no measurable impact on shad populations, they are susceptible to commercial overfishing. Because of their highly migratory life history and their recreational and commercial importance, American shad are co-managed by the U.S. Fish and Wildlife Service, the National Marine Fisheries Service, and state fisheries agencies. The Atlantic States Marine Fish Commission serves as a key forum for coordinating the collective effort to conserve American shad.

Early 19th century shad fishing on the Peedee (Greater Pee Dee) River, South Carolina

Shad are also valued as a sport fish that exhibit complex and little-understood feeding behaviors while spawning. Unlike salmon, shad retain the ability to digest and assimilate food during the anadromous migration. Like other fish, their feeding instinct can be triggered by a variety of factors such as turbidity and water temperature.

Shad serve notable symbolic roles in regional politics and culture. On the year of every gubernatorial election, would-be candidates, lobbyists, campaign workers, and reporters gather in the town of Wakefield, Virginia, for Shad Planking. Similarly, in Connecticut, the towns of Essex and Windsor hold annual shad festivals. Each spring, the town of Lambertville, New Jersey, on the Delaware River across from New Hope, Pennsylvania, also hosts an annual Shad Festival. There is a shad museum on the Connecticut River in Haddam, Connecticut.

William Penn negotiated with the Lenape for the shad fishing ground Schuylkill in the 1680s. Shad, he said, were "excellent Pickled or Smoked."[13]

• Farmer, Fannie Merritt (1901). The Boston Cooking-School Cook Book (3rd ed.). Boston: Little, Brown, and Company. p. 156. Retrieved 4 December 2022 – via Google Books. "Fried Shad Roe" recipe.
• Village Voice article, "Shad Madness".
• New England Shad Association
• Media related to Alosa sapidissima at Wikimedia Commons