About Alosa chrysochloris (Rafinesque, 1820)
The skipjack herring, also known as Alosa chrysochloris, is a migratory North American fish that lives in fresh and brackish water and belongs to the herring family Alosidae. Its common name skipjack shad comes from its common behavior of leaping out of the water while feeding. Other common names for this species include blue herring, golden shad, river shad, Tennessee tarpon, and McKinley shad. Skipjack shad are restricted to Gulf of Mexico drainage basins, and they live in clear to moderately turbid water in areas with flow. As a migratory species, dams often block their reproduction. Records show the species was much more abundant in the Upper Mississippi River basin before the river was impounded. Today, skipjack herring are most abundant in the upper Mississippi River below the mouth of the Ohio River. They are classified as an "early-run" species, because they migrate to spawn in early spring. Currently, skipjack herring are limited to the Gulf of Mexico and its drainage basins within the United States. These drainage basins include the Mobile River basin, the ACF basin (Apalachicola/Chattahoochee/Flint River), the Mississippi basin, and the Rio Grande basin. Records confirm the species was more abundant in the upper Mississippi River before impoundment, with the largest current population found in the upper Mississippi River below the mouth of the Ohio River. In recent years, human modifications to the middle Missouri River have created more favorable conditions for skipjack shad, and their distribution has expanded upstream to the Nebraska-South Dakota border. Historically, skipjack herring lived in the northern upper Mississippi River and the St. Croix River, but only four records of the species in Wisconsin waters exist since the 1950s. Dams have reduced this migratory species' range, as it cannot migrate northward past dams, making skipjack herring rare in the upper reaches of Gulf of Mexico drainages. Skipjack herring are a migratory schooling euryhaline species that can enter both brackish and freshwater bodies. They can be anadromous, but are not required to be, as they can complete their entire life cycle in freshwater. They migrate extensively within rivers, and prefer fast flowing water where they are well known for leaping. They inhabit clear to moderately turbid waters in large rivers and reservoirs, typically within current over sand or gravel substrate. One study documented skipjack herring feeding on other shad and herring species, including threadfin shad, gizzard shad, and young-of-the-year herring. In extreme cases, they have been observed relying on cannibalism to survive. They also feed on small fishes, mostly shad, while juvenile skipjack herring feed on insects. The maximum size of shad or herring eaten by skipjack shad is approximately 30–35% of the skipjack's own body length. Little data exists on the predators of skipjack shad, but larger fish species, seabirds, and humans are known to prey on them. In fact, documented data shows that fish in the family Clupeidae, including skipjack herring, make up as much as 45% of the diet of these predatory seabirds.
