American shad have sharp scales on their stomach and chest like a saw. Their body is thin from side to side and long from top to bottom. Their backs are shiny blue, and their bellies are white. They have one or more black spots in a row on their shoulder. Once in a while, they have two rows of black spots. American shad get darker in color when they go into rivers to lay their eggs. On average, American shad are 55.85 cm long, but they can be anywhere from 45 to 76.2 cm long. On average, they weigh 2.5 kg, but they can weigh anywhere from 0.9 to 5.4 kg. Females are usually 3 times bigger than males. (Ford, 2006)
American shad live in temperate areas, so they are found north of the tropics but south of the Arctic. They spend most of their lives near the coasts of the Atlantic or Pacific Ocean. When they are ready to breed, which is called spawning, they travel into the rivers of the United States, Canada, or Mexico to lay their eggs. American shad are native to the Atlantic Ocean. They are found from Newfoundland, Nova Scotia and the St. Lawrence River in Canada, down to central Florida. In the late 1800's, they were introduced into the Pacific Ocean, where they now live as well. Today, American shad can be found as far north as Cook Inlet and the Kamchatka Peninsula in Alaska, and down to Baja California in Mexico. (Eddy, 1957)
Adult American shad swim more than 19,000 km in their lifetime, so they travel through many habitats. In summer and fall, American shad are found in waters along the coast, from 0 to 250 m deep. In winter months, they usually stay in deeper water away from the coast up to 375 m. American shad migrate, traveling into rivers to lay their eggs. (Eddy, 1957)
Adult American shad lay their eggs, called spawning, in rivers in the late winter. The eggs usually hatch in 10 days. In warm rivers, they can sometimes hatch in 7 days. When they hatch, larvae are 10 mm long on average. In late fall or early winter, the juveniles travel from the rivers out into the ocean. In 2 to 5 years, they go back to the same river to spawn. (Glebe, 1981)
In late winter, American shad travel into rivers of the United States, Canada, and Mexico to lay their eggs, or spawn. One or more males chase a female up a river. They sometimes nudge her in the belly until she releases her eggs in open water. Then, the males fertilize the eggs in the water. The eggs come apart from each other and sometimes float many kilometers before they hatch. Because the eggs can move, they don't all get eaten if they're found by a predator. (Page, 1991; Wiley, 1986)
Female American shad lay eggs for the first time when they are about 4 years old, but it can be any time from 3 to 7 years old. All together, females release 200,000 to 250,000 eggs every year. Each fish lays 2 to 150 eggs each season. They release the eggs in cycles as they travel up the river. A cycle can last a couple days or up to a week. After the cycle, females rest for 1 to 3 days and start laying eggs again. Juvenile American shad hatch after 6 to 10 days and are able to be independent from their parents right away. (Crossman, 1998; Pfeiffer, 2002)
American shad live about 9 years in the wild, but can live anywhere from 6 to 10 years. Traveling from rivers to the ocean is hard on their bodies, and many of them die. About 60% of females die in the season that they migrate. American shad live about 6 years in captivity, but can live 4 to 7 years. (Eddy, 1957; Ford, 2006; Weiss-Glanz,, 1972)
American shad are social animals that swim in groups, or schools. As juvenile American shad travel to the ocean, they avoid bigger fish which eat them. As they get bigger and reach the ocean, they live closer together with other fish. (Crecco, 1985; Ford, 2006)
American shad are not territorial. They don't stay within the same area, because they travel between rivers and the ocean.
American shad can hear sounds with frequencies up to 180 kHz, and they often escape predators that communicate with these same high-frequency noises. American shad communicate with females by chasing them and nudging them in the belly. (Crossman, 1998; Plachta, 2003)
Juvenile American shad eat both plants and animals, mostly zooplankton and larvae of insects. Juveniles eat more after they leave their birthplace. As they get older, American shad start to eat small fish, crustaceans, plankton, worms, and occasionally fish eggs. They eat very little or no food when they are migrating and during the late winter. They start to eat normally again in spring when the water warms up. (Weiss-Glanz,, 1972)
Adult American shad get darker in color when they go into rivers to spawn. This helps them blend into their environment. American shad can hear ultrasound, which are really high frequency noises made by their predators like longbeaked common dolphins and common dolphins. They hide or swim away when they hear these noises. also have the ability to detect ultrasound. They are also eaten by striped bass, blue fish, smallmouth bass, walleye and channel catfish. In addition, they are also eaten by bears and some birds. Finally, humans hunt and eat them. (Crecco, 1985; McPhee, 2003)
American shad are prey for bigger fish, some birds, humans, bears, and dolphins. However, none of these predators depend on American shad to survive. American shad also eat lots of crustaceans and fish that live in rivers while they are migrating. They may help control numbers of some of these animals. American shad get different parasites, like roundworms and flatworms. American shad that spawn in the northwestern United States can also temporarily carry another kind of roundworms. In the southern Atlantic, American shad are often infected by another kind of flatworm. (Shields, 2002; Zool, 1993)
Humans have fished American shad for their meat and eggs for hundreds of years, but the number of them has decreased a lot from overfishing and damage to their habitat. As a result, U.S. and state governments reduced the number that can be fished and passed laws to protect the rivers where they live. In some places, humans have started to raise them. In others, engineers modified dams to allow them to migrate up the rivers. (Dicenzo, 1995; Marcy, 2004)
Sean Kessler (author), Radford University, Karen Powers (editor), Radford University, Gail McCormick (editor), Animal Diversity Web Staff, Catherine Kent (editor), Special Projects.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
uses electric signals to communicate
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
mainly lives in water that is not salty.
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
makes seasonal movements between breeding and wintering grounds
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
small plants that float or drift in great numbers in fresh or salt water, especially at or near the surface. These serve as food for many larger organisms. (Compare to zooplankton.)
an animal that mainly eats fish
Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
uses sound above the range of human hearing for either navigation or communication or both
uses sight to communicate
small animals that float or drift in great numbers in fresh or salt water, especially at or near the surface. These serve as food for many larger organisms. (Compare to phytoplankton.)
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