American Shad, Alosa sapidissima
American Shad, Alosa sapidissima, Juvenile. Fish caught from the Willamette River, Portland, Oregon, September 2018. Length: 7.9 cm (3.1 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.
American Shad, Alosa sapidissima. Fish caught in the Arlington, Virginia, May 2014. Length: 36 cm (14 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
American Shad, Alosa sapidissima. Fish caught in the Cooper River, South Carolina, March 2011. Length: 51 cm (20 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.
The American Shad, Alosa sapidissima, is a member of the Herring or Clupeidae Family, and is known in Mexico as sábalo americano. Globally, there are twenty-three species in the genus Alosa with this species being the only species found in Mexican waters and within the Pacific Ocean.
The American Shad has a moderately deep, fusiform, and compressed body with a depth that is 27% to 31% of standard length. They are silvery with a blue-green metallic sheen dorsally and transition to white ventrally with one or more dark spots adjacent to the top of their gill covers. Their head has small eyes and an oblique mouth that opens at the front. Their anal fin is short with 18 to 24 rays and is located well behind the dorsal fin; their caudal fin is forked; and, their dorsal fin has 15 or 19 rays and is located before the center of the body. They have over 60 long slender gill rakers. Their belly has a distinct keel.
The American Shad is a small coastal pelagic species found on the surface during summer months and at depths up to 250 m (820 feet) at other times of the year. They reach a maximum of 76 cm (2 feet 6 inches) in length and 5.5 kg (12 lbs) in weight. They are dimorphic with females being as much as three times larger than males. As of March 31, 2023, the International Game Fish Association world record for length stood at 54 cm (1 foot 9 inches) with the fish caught from coastal waters off Narrowsburg, New York in May 2013. The corresponding world record for weight stood at 5.1 kg (11 lbs 4 oz) with the fish caught in Massachusetts in May 1986. They are widely distributed, common, and locally abundant forming large schools. They are highly migratory and are believed to travel over 19,000 km (12,000 miles) during their lifetime. They mostly consume plankton (copepods and mysids) and occasionally feed on small fish; they are believed to help control the populations of the species they consume. They have the ability to detect sound, which helps them avoid predation, however, they are important forage fish for large predatory fish, dolphins, bears, birds, and humans. They make annual migrations of up to 630 km (400 miles) to freshwater rivers for reproduction. Populations vary from iteroparous, making several spawning trips to freshwater, to semelparous, making one trip for spawning and then dying. Reproduction is oviparous with each female releasing eggs in batches of 30,000 that are fertilized externally, with a total annual egg production of 200,000 to 600,000 per female. Adults return fairly quickly to the ocean after spawning and virtually disappear moving to deeper waters in the winter. Eggs are pelagic and can move independently for several miles downstream where they hatch within ten days. Young collect in large schools and return to the ocean in autumn arriving as 3.8 cm (1.5 inches) to 11.4 cm (4.5 inches) miniature adults. They have lifespans of up to thirteen years.
The American Shad was introduced to the Sacramento River in the 1870s and can now be found in Mexican waters of the Pacific Ocean as far south as Todos Santos, Baja California Sur.
The American Shad is most likely confused with the Alewife, Alosa pseudoharengus (steeply rising lower jaw; large eyes; less than 60 gill rakers).
From a conservation perspective the American Shad is currently considered to be of Least Concern with stable, widely distributed populations. Their global populations are currently in excess of 1,000,000 individuals, however, they have been recently subject to significant declines due to overfishing and habitat destruction (dams). They are considered to have both commercial and recreational value. They are caught by hook and line on spinning gear and fly fishing tackle, by cast nets during migration runs, and as a by-catch of menhaden and shrimp trawlers. They have been a major food fish of Native Americans for centuries, however, they are prone to infection by a wide variety of nematodes. Shad roe is considered a delicacy. They are being bred in fish hatcheries in a variety of locations.