Skipjack herring
The skipjack herring (Alosa chrysochloris) is a North American, migratory, fresh- and brackish water fish species in the herring family Clupeidae. The name skipjack shad comes from the fact that it is commonly seen leaping out of the water while feeding. Other common names include blue herring, golden shad, river shad, Tennessee tarpon, and McKinley shad. The skipjack shad is restricted to the Gulf of Mexico drainage basins. Skipjack are found in clear to moderately turbid water in areas with flow. Because they are a migratory species, dams often impede their reproduction. Records suggest that this species was much more abundant in the Upper Mississippi River basin before it was impounded. Currently, skipjack is most abundant in the Upper Mississippi River below the mouth of the Ohio River. They are known as an "early-run" species as they migrate to spawn in the early spring.
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NocturnalNocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal",...
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InsectivoresAn insectivore is a carnivorous plant or animal that eats insects. An alternative term is entomophage, which also refers to the human practice of e...
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PiscivoresA piscivore is a carnivorous animal that eats primarily fish. Piscivorous is equivalent to the Greek-derived word ichthyophagous. Fish were the die...
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PlanktivoreA planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton. Phytoplankton are usually photosynthet...
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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PolyandryPolygyny is a mating system in which one female lives and mates with multiple males but each male only mates with a single female.
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MonogamyMonogamy is a form of relationship in which both the male and the female has only one partner. This pair may cohabitate in an area or territory for...
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PolygynyPolygyny is a mating system in which one male lives and mates with multiple females but each female only mates with a single male.
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MigratingAnimal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migrati...
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starts withCurrently skipjack herring are restricted to the Gulf of Mexico and its drainage, in the United States. The Gulf of Mexico drainage includes the Mobile River basin, the ACF basin (Apalachicola/Chattahoochee/Flint River), the Mississippi basin, and the Rio Grande basin. Records indicate that this species was more abundant in the upper Mississippi River before it was impounded, and currently skipjack herring are most abundant in the upper Mississippi River below the mouth of the Ohio River. In recent years, human modifications to the middle Missouri River have made conditions more favorable for skipjack shad and their distribution has expanded upstream to the Nebraska-South Dakota border. Skipjack herring were historically found in the northern upper Mississippi River and the St. Croix River; however, there have only been four records of skipjack shad in Wisconsin waters since the 1950s. Because this fish is a migratory species, dams have diminished its distribution. It cannot continue to migrate northward over dams; therefore it is rare to see a skipjack in the upper reaches of the Gulf of Mexico drainages.
Skipjack herring are a migratory schooling species. They are a euryhaline species that can enter brackish and freshwater bodies. They can be anadromous but are not obligated to be because they can complete their life cycle in freshwater. Skipjack shad are strongly migratory within rivers and prefer fast flowing water where they are renowned for leaping. They are found in clear to moderately turbid waters in large rivers and reservoirs usually within the current over sand or gravel. In one study, skipjack herring have been found to feed on other shad/herring species such as the threadfin shad, the gizzard shad and young of the year herring species. In some extreme cases, it was shown that they could rely on cannibalism to survive. They are also known to feed on small fishes, mostly shad, while the juveniles feed on insects. The maximum size of the shad/herring utilized by skipjack shad was found to be about 30-35% of the skipjack's body length. There is not much data on the predators of the skipjack shad. Larger fish species, seabirds, and humans prey upon them. In fact, it is shown that fish species in the family Clupeidae including the skipjack herring comprise up to 45% of the diet of these avian species.
The spawning season for skipjack herring is from early March to late April in the southern extent of its range. In the upper Mississippi river drainage spawning time is from early May to early July. Females produce about 100,000 to 300,000 eggs per year, presumably after 2 to 3 years of growth with an average size being 11.8 inches (30 cm) Spawning is thought to occur in the depths of main channel over coarse sand-gravel bars. Spawning temperature range is between 16 and 21 °C (61 and 70 °F). Eggs are broadcast over the substrate. Skipjack shad young may reach total lengths of 75–150 millimetres (3.0–5.9 in) during their first year. The maximum length in adults is 20 inches, but they are most commonly found to be between 12 and 18 inches (300–460 mm). The oldest specimen of skipjack herring reported was four years old. High population rates and the fact that there it has little to no interest to fisheries tells us that humans do not have much influence on life history. Impoundments have changed their distribution slightly, but they have no trouble spawning as a result.
