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Alosa chrysochlorisBlue herring(Also: Golden shad; Green herring; River herring; Skipjack)

By Dylan Chandler

Geographic Range

Skipjack herring, or skipjack shad (Alosa chrysochloris), range from the Red River drainage (Hudson Bay basin) and Mississippi River basin from central Minnesota, south to the Gulf of Mexico. Skipjack herring also range widely throughout the eastern United States and can be found from Florida to Texas. Occasionally, these fish are found in brackish, to marine water environments, especially along the gulf coast. ("Alosa chrysochloris", 2009; Morrison, 2009; NatureServe, 2005)

Habitat

Skipjack herring are large river fish that prefer to reside in clear, deep, and swift waters over gravel or sand. These fish most often travel in large schools, partly for protection from larger predatory species. Skipjack herring are not generally found on the bottom of the river, and they avoid muddy or cloudy waters whenever possible. They frequently "skip" along the surface of the water when migrating in early spring. Skipjack herring are known to congregate in swift currents below dams. Unlike many members of family Clupeidae, skipjack herring are not required to be an anadromous species. These fish spend most of their life cycle in rivers and occasionally in coastal marine estuaries. Skipjack herring migrate upstream in the spring to spawn, sometimes traveling very long distances. The addition of dams in many areas has impeded their ability to migrate further upstream. This has resulted in their disappearance in many areas where they were once present such as in Minnesota. (MN DNR, 2013; Morrison, 2009)

Physical Description

Skipjack herring have a slender, compressed body and can reach a maximum length of 21 inches. These fish have a large mouth and pointed snout with a protruding lower jaw, which is distinctive from other similar species. Skipjack herring have teeth in both jaws as well as two to four rows on their tongue. They are gray dorsally and silver or white laterally and ventrally. At times, skipjack herring can appear to have a blue reflection coming from their sides. These fish also have yellow eyes with protective eye lid covers. Skipjack herring have modified scales on their slender body. These scales are referred to as "scutes" and form a saw-tooth margin around the belly, which distinguishes skipjack herring from other similar species. ("Skipjack Herring", 2012; MN DNR, 2013)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    420 to 1588 g
    14.80 to 55.96 oz
  • Average mass
    453 g
    15.96 oz
  • Range length
    250 to 550 mm
    9.84 to 21.65 in
  • Average length
    250-450 mm
    in

Development

Skipjack herring complete their entire life cycle in fresh water. Information regarding their spawning patterns is very limited; however, skipjack herring are thought to spawn in the deepest channels over coarse gravel or underwater sandbars. Juveniles feed on zooplankton, insect larvae, and small fishes, fish consumption increases proportionately with size. Juvenile skipjack herring reach lengths of 75 to 150 mm during their first year of life. Sexual maturity occurs at about 300 mm. Immediately after hatching, skipjack herring are on their own and many are eaten by predatory fish. Juveniles that survive the first few months of life have greatly increased chances of survival. Skipjack herring typically stop growing after reaching 21 inches in length, which means they do not have indeterminate growth. ("Herring Family: Clupeidae", 2008; Hassan, 2013)

Reproduction

Very little information is available regarding the spawning patterns of skipjack herring. These fish are unique in family Clupeidae, as not all skipjack herring make an anadromous journey. In general, members of family Clupeidae spawn in the spring, once water temperatures have warmed to between 11 and 27° Celsius. Before spawning, skipjack herring typically travel a long distance. Due to the water temperature requirements, spawning typically occurs earlier at lower latitudes and later at higher latitudes. Female clupeids typically reach the spawning grounds before males, where the oldest females spawn first. Since clupeids travel in schools, they do not have a problem finding or attracting mates. These fish typically form mating pairs, or groups of three. Females drop their eggs in moderately deep, to very deep areas over gravel, while males simultaneously fertilize them with sperm. ("Herring Family: Clupeidae", 2008)

Female skipjack herring reach sexual maturity in approximately three years, while males are thought to mature in two years. Females are thought to lay between 100,000 and 300,000 eggs every spring after their migration. Mature skipjack herring immediately leave the spawning site once the spawn is complete. Larvae hatch in 58 hours at 17.2° Celsius. The average larval length after hatching is roughly 3.4 to 3.6 mm. After the spawn concludes, larval skipjack herring are immediately on their own. (Ross, 2001)

  • Breeding interval
    Skipjack herring breed once a year after the spring migration.
  • Breeding season
    Skipjack herring typically spawn from early May through July.
  • Range number of offspring
    100,000 to 300,000
  • Average number of offspring
    150,000
  • Range time to hatching
    3 to 6 days
  • Average time to hatching
    6 days
  • Range time to independence
    Immediatley (low) minutes
  • Range age at sexual or reproductive maturity (female)
    3 to 4 years
  • Average age at sexual or reproductive maturity (female)
    3 years
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

Skipjack herring give no parental care after the young hatch; they immediately leave the spawning grounds and begin the journey back to their original habitat location. Larval skipjack herring spend the summer in the shallows and in the fall, they move to large groups in the main channel for protection. ("Skipjack Herring", 2012)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

Not much is known about the lifespan of skipjack herring. However, many species in family Clupeidae commonly live to 10 years of age. Most skipjack herring do not live past the first few months of life, around 90% die within the first year of life. Once skipjack herring make it past the first year of life, their chances of survival begin to increase with their increasing size. The biggest threat to the longevity of skipjack herring is predation. Many species prey upon skipjack herring as their primary diet. ("Herring Family: Clupeidae", 2008; Coad, 1997)

  • Typical lifespan
    Status: wild
    1 to 10 years
  • Average lifespan
    Status: wild
    6 years

Behavior

Schools of skipjack herring drive minnows to the surface for easy capture and often leap out of the water when feeding. These fish often congregate in large numbers below dams in the spring, presumably attempting to migrate upstream to spawn. Skipjack herring vertically migrate daily, this means they move up and down the water column at certain times of the day in search of food. ("Assessment of Migratory Stocks", 2011; MN DNR, 2013)

Home Range

The home range of skipjack herring includes the Mississippi River. Skipjack herring often migrate up tributaries to spawn, but they typically retreat to the Mississippi River after the spawn due to the relatively steady water levels, large main channel, and swift moving water. There is currently no information available regarding the territory size maintained by these fish. (MN DNR, 2013)

Communication and Perception

Little to no information is known about the communication of skipjack herring besides their feeding and mating behavior. Their yellow eyes are thought to help them find other skipjack herring for mating. Likewise, their yellow eyes also help them locate their prey in low light conditions. ("Herring Family: Clupeidae", 2008)

  • Communication Channels
  • visual

Food Habits

The diet of skipjack herring includes: plankton and small fishes, primarily minnows, goldeneyes, and gizzard shads. Skipjack herring also feed on insects such as mayflies and caddisflies. Feeding typically occurs in schools, this species commonly crowds minnows to the surface before preying upon them. (MN DNR, 2013; Ross, 2001)

  • Animal Foods
  • fish
  • insects

Predation

Skipjack herring are considered forage fishes and have many predators. Their biggest advantage over larger fish is that they travel in schools, making it harder for the predator to locate them. However, this also means when they are found, the predator species may go into a feeding frenzy, eating many at once. ("Alosa chrysochloris", 2009)

Ecosystem Roles

Skipjack herring are an important host for the parasitic larvae of native ebony shell mussels. The loss of skipjack herring in the upper Mississippi River resulted in the loss of ebony shell mussels. Skipjack herring are also one of the main food sources for all predatory fish in the Mississippi River system. (Ross, 2001)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Skipjack herring can be eaten by people, but they are generally considered a 'rough fish' because they are difficult to debone. These fish are caught by commercial fisherman to sell and use for bait to catch preferred game fish. Although skipjack herring do not have a very large economic purpose, they provide a quality food source for many desired game fish. Game fishing is a very large industry and attracts people from all over the country. (Morrison, 2009)

Economic Importance for Humans: Negative

Skipjack herring are not known to create any negative effects for humans.

Conservation Status

According to the IUCN Red List, CITIES appendices, and the United States Endangered Species Act, there is no immediate concern for skipjack herring. Their population size remains very stable except in areas where dams have cutoff migration, near Minnesota and Wisconsin. (NatureServe, 2005)

Other Comments

Skipjack herring are the sole host for the larval stages of two endangered mussel species in Minnesota, ebony shells and elephant-ears. These fish permit these two mussel species to complete their life cycle. The reestablishment of skipjack herring would allow ebony shell and elephant ear mussels to return to Minnesota. Lock and dam structures limit the spring migration of skipjack herring. To reestablish these fish in Minnesota, fish passage features such as ladders or lifts will be needed at several lock and dam sites between Iowa and central Minnesota. (MN DNR, 2013)

Contributors

Dylan Chandler (author), Minnesota State University, Mankato, Robert Sorensen (editor), Minnesota State University, Mankato, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

Glossary

Atlantic Ocean

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.

World Map

Nearctic

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.

World Map

bilateral symmetry

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. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

ecotourism

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.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

insectivore

An animal that eats mainly insects or spiders.

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

piscivore

an animal that mainly eats fish

planktivore

an animal that mainly eats plankton

polyandrous

Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).

polygynous

having more than one female as a mate at one time

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

visual

uses sight to communicate

References

U.S. Geological Survey. Alosa chrysochloris. 489. Gainesville, Florida: U.S. Department of the Interior. 2009.

2011. "Assessment of Migratory Stocks" (On-line). Accessed March 26, 2013 at http://www.fao.org/docrep/W5449E/w5449e0d.htm.

2008. "Herring Family: Clupeidae" (On-line). Accessed March 25, 2013 at http://images.library.wisc.edu/EcoNatRes/EFacs/FishesWI/reference/econatres.fisheswi.i0022.pdf.

2012. "Skipjack Herring" (On-line). Accessed March 25, 2013 at http://www.seagrant.wisc.edu/home/Default.aspx?tabid=605&FishID=135.

Coad, B. 1997. "Shad Journal" (On-line). Accessed March 26, 2012 at http://www.cbr.washington.edu/shadfoundation/shad/JOURNAL2/vol2n4.pdf.

Hassan, C. 2013. "Skipjack herring" (On-line). Accessed March 25, 2013 at http://txstate.fishesoftexas.org/alosa%20chrysochloris.htm.

MN DNR, 2013. "Species profile: Minnesota DNR" (On-line). Accessed March 25, 2013 at http://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=AFCFA01030.

Morrison, S. 2009. Skipjack Herring. Wildlife Diversity Notebook, Spring 2009: 9.

NatureServe, 2005. "Comprehensive Report Species" (On-line). Accessed March 25, 2013 at http://www.tnfish.org/SpeciesFishInformation_TWRA/Research/SkipjackHerring_AlosaChrysochlorisInformation_NS.pdf.

Ross, S. 2001. The Inland Fishes of Mississippi. Mississippi: Sport Fish Restoration.

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