American shad have the ability to detect ultrasonic signals up to 180 kHz. They are often able to escape predators that use ultrasonic signals for communication. Male American shad communicate to females to release their eggs by chasing and nudging the female's belly.
Communication Channels: visual ; electric
Perception Channels: visual ; tactile ; ultrasound ; chemical
American shad have been harvested for meat and eggs for hundreds of years. However, overfishing and habitat destruction have dramatically reduced populations of this species. Both state and federal governments have limited anthropogenic changes to rivers with shed populations and have imposed stricter fishing limits. Hatcheries of American shad have been created by state governments and private organization in a number of states. Dams and rivers that once stopped shad from traveling up rivers to spawn are now equipped with passages to enable migration.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Adult American shad spawn in rivers during late winter. On average, larvae hatch in 10 days. In rivers of higher temperature, larvae may hatch in as little as a week. Newly-hatched larvae average 10 mm long. In late fall or early winter, juveniles make their way from rivers into the ocean. In 2 to 5 years, adult American shad return to their natal rivers to spawn.
There are no known adverse affects of American shad on humans.
American shad are a sport fish and are also bred in hatcheries. Both their roe and meat are consumed. This species may also encourage ecotourism, drawing sport fishermen.
Positive Impacts: food ; ecotourism
American shad are preyed upon by bigger fish, some birds, humans, bears, and dolphins. However, these predators are not dependent on this species. American shad also eat many riverine crustaceans and fish during migration and may regulate populations of some species. American shad are hosts to a variety of parasites, including nematodes (Hysterothylacium aduncum) and cestodes (Scolex pleuronectis). Individuals that migrate to spawn in northwestern United States are occasionally infected by nematodes (Anisakis simplex), for which American shad act as an intermediate host. In the southern Atlantic, American shad are often infected by one species of trematode (Genitocotyle atlantica).
Commensal/Parasitic Species:
Juvenile American shad are omnivores with a diet consisting of mostly zooplankton and insect larvae. Juveniles eat more once they have left spawning areas. As they get older, American shad broaden their diet to include small fish, crustaceans, plankton, worms, and occasionally fish eggs. During migration in the late months of winter, American shad eat very little food, if any. However, as water temperatures increase in spring, their diet returns to normal.
Animal Foods: fish; eggs; zooplankton
Plant Foods: phytoplankton
Primary Diet: carnivore (Piscivore , Eats non-insect arthropods)
American shad are restricted to temperate climates and spend the majority of their lives in coastal areas of the Atlantic or Pacific Ocean. During spawning season, American shad travel to the rivers of the United States, Canada, and Mexico to lay their eggs. American shad are native to the Atlantic Ocean, ranging from Newfoundland, Nova Scotia and the St. Lawrence River in the north, to areas of coastal central Florida in the south. In the late 1800's, humans introduced American shad to the Pacific Ocean. Today, American shad can be found as far north as Cook Inlet, Alaska and the Kamchatka Peninsula and south to Baja California, Mexico.
Biogeographic Regions: nearctic (Native ); atlantic ocean (Native ); pacific ocean (Introduced )
Adult American shad are predicted to swim over 19,000 km in their lifetime, during which they are found in many habitats. During summer and fall, American shad can be found in coastal waters, generally at depths from 0 to 250 m. During the winter months, they generally inhabit deeper ocean waters away from the coast at depths up to 375 m. American shad are a migratory species, and toward the end of winter they travel into rivers to spawn.
Range depth: 0 to 375 m.
Average depth: 125 m.
Habitat Regions: saltwater or marine ; freshwater
Aquatic Biomes: rivers and streams; coastal
American shad have a life expectancy of 6 to 10 years in the wild (average 9 years). Migration from rivers to the sea places a heavy toll on their bodies, and increased migration increases mortality. Migrating females have an average mortality rate of 60 % during seasons in which they migrate. In captivity, American shad are expected to live 4 to 7 years (average 6 years).
Range lifespan
Status: wild: 7 to 12 years.
Average lifespan
Status: wild: 10 years.
Range lifespan
Status: captivity: 4 to 10 years.
Typical lifespan
Status: wild: 6 to 10 years.
Average lifespan
Status: wild: 9 years.
Typical lifespan
Status: captivity: 4 to 7 years.
Average lifespan
Status: captivity: 5 years.
The stomach and chest of American shad have sharp scales similar to that of a saw. They have a compressed body, which is dorsally blue and metallic in color and ventrally white. American shad have one or more black spots in a row on their shoulder. Though rare, some American shad have two rows of black spots. When American shad enter rivers to spawn, their colors darken. American shad on average measure 55.85 cm in length and can range from 45 to 76.2 cm. On average, they weigh 2.5 kg and can range from 0.9 to 5.4 kg. Females are typically three times larger in mass than males.
Range mass: 0.9 to 5.4 kg.
Average mass: 2.5 kg.
Range length: 45 to 76.2 cm.
Average length: 55.85 cm.
Sexual Dimorphism: female larger
Other Physical Features: bilateral symmetry
Adult American shad darken in color on entering rivers to spawn, which helps them blend into their environment. American shad also have the ability to detect ultrasound. When shad detect ultrasound use of predators, such as their major predators, dolphins (Delphinus capensis and Delphinus delphis), American shad hide or flee. Other predators include: striped bass Morone saxatilis, blue fish Pomatomus saltatrix, smallmouth bass Micropterus dolomieu, walleye Sander vitreus and channel catfish Ictalurus punctatus. Additionally, bears and some birds eat American shad. This species is also a sport fish and is consumed by humans.
Known Predators:
Anti-predator Adaptations: cryptic
In the late months of winter, American shad enter freshwater rivers of the United States, Canada, and Mexico to spawn. One or more males chase a female up a river and may also nudge her belly until the female releases her eggs in open water. The pursuing males then fertilize the eggs. The eggs separate from each other and may drift many kilometers before they hatch. This mobility of eggs may increase survival rates, as eggs are not all at risk in one location if discovered by a predator.
Mating System: polyandrous
Female American shad spawn for the first time between 3 and 7 years of age (average 4 years). In total, females release 200,000 to 250,000 eggs each year. Individual American shad lay 2 to 150 eggs each season, which are released in cycles as females travel up the river. A cycle lasts from a couple of days to a week and is followed by 1 to 3 days of rest, after which she begins a new cycle. Juveniles hatch after 6 to 10 days and are independent on hatching.
Breeding interval: American shad spawn once a year.
Breeding season: American shad spawn from late winter to early spring.
Range number of offspring: 2 to 150.
Average number of offspring: 77.
Range gestation period: 6 to 10 days.
Average time to independence: 0 minutes.
Range age at sexual or reproductive maturity (female): 3 to 7 years.
Average age at sexual or reproductive maturity (female): 4 years.
Range age at sexual or reproductive maturity (male): 3 to 7 years.
Average age at sexual or reproductive maturity (male): 4 years.
Key Reproductive Features: seasonal breeding ; sexual ; fertilization (External ); oviparous
Adult American shad do not provide any care for the eggs or larvae after fertilization.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female)
The American shad (Alosa sapidissima) is a species of anadromous clupeid fish naturally distributed on the North American coast of the North Atlantic, from Newfoundland to Florida,[2] and as an introduced species on the North Pacific coast. The American shad is 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.[3]
The American shad has been described as "the fish that fed the (American) nation's founders".[4][5] Adult shad weigh between 1.5 and 3.5 kg (3 and 8 lb), and they have a delicate flavor when cooked.[6] 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 shads (females) are prized because the eggs are considered a delicacy.[7]
The name "shad" derives from the Old English sceadd, meaning "herring"; it is a cognate to Irish, Welsh, and Scottish Gaelic words for herring.[8]
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.
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.
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.
American shad were introduced into the San Francisco Bay/Sacramento River system in California in the 1800s, and they have spread throughout many river systems on the West Coast of North America. A large shad population occurs in the Columbia River. In recent years, shad counts at Bonneville and The Dalles Dams have ranged from over two million to over five million fish per year. Spawning shad return to the Columbia in May and June and migrate above Lower Granite Dam on the Snake River and above Priest Rapids Dam on the Upper Columbia. Unlike many introduced species, American shad have not been confirmed to have serious negative effects on the environment or other native fish species in the Columbia.[2]
American shad are also occasionally found on the Northwest Pacific coast in Kamchatka, Russia.[12]
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]
The American shad (Alosa sapidissima) is a species of anadromous clupeid fish naturally distributed on the North American coast of the North Atlantic, from Newfoundland to Florida, and as an introduced species on the North Pacific coast. The American shad is 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.
The American shad has been described as "the fish that fed the (American) nation's founders". Adult shad weigh between 1.5 and 3.5 kg (3 and 8 lb), 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 shads (females) are prized because the eggs are considered a delicacy.
The name "shad" derives from the Old English sceadd, meaning "herring"; it is a cognate to Irish, Welsh, and Scottish Gaelic words for herring.
