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Coregonus zenithicusLake Superior longjaw(Also: Light-back tullibee; Longjaw cisco; Pale-back tullibee)

By Meg Claypool

Geographic Range

The range of shortjaw ciscoes (Coregonus zenithicus) has been drastically reduced over the years. These fish are currently found east of the Northwest Territories in Canada, and as far south as Wisconsin and Michigan. Lake Superior is the only Great Lake known to still have populations of shortjaw ciscoes, however, at one time, they were reported in all Great Lakes except Lake Ontario. Shortjaw ciscoes are currently reported in 22 lakes in Canada, from Ontario to the Northwest Territories. ("Minnesota Department of Natural Resources website", 2013; "NatureServe Explorer: An online encyclopedia of life [web application]", 2012; "Shortjaw cisco", 2008; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

Habitat

Shortjaw ciscoes are found in deep waters of large lakes, ranging from depths of 20 to 150 m. During spawning season, they are found at shallower depths, ranging from 37 to 72 m. (Gimenez Dixon, 1996; "Minnesota Department of Natural Resources website", 2013; "NatureServe Explorer: An online encyclopedia of life [web application]", 2012)

  • Aquatic Biomes
  • lakes and ponds
  • Range depth
    20 to 150 m
    65.62 to 492.13 ft

Physical Description

In the deep waters where shortjaw ciscoes thrive, they can grow in length up to 35 cm and weigh up to 1.0 kg. They have an olive green tint on their dorsal side and white coloration ventrally. As adults, their fin colors darken with a black tint on both pelvic and anal fins. Shortjaw ciscoes have an elliptically-shaped body, with a distinguishing straight snout. Females tend to be larger than males. Shortjaw ciscoes have 45 gillrakers. Their snouts are larger than expected compared to their proportional, average-sized eyes. (Murray, 2006; "NatureServe Explorer: An online encyclopedia of life [web application]", 2012; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

  • Sexual Dimorphism
  • female larger
  • Range mass
    270 to 1000 g
    9.52 to 35.24 oz
  • Average mass
    >300 g
    oz
  • Range length
    28 to 40 cm
    11.02 to 15.75 in
  • Average length
    33 cm
    12.99 in

Development

Shortjaw ciscoes spawn in both the spring and fall. Juveniles grow fast during the first year of life, after which, the growth rate slows down. Over their lifetime, females tend to grow heavier than males. Depending on the lake, these fish reach maturity at different ages; however, most fish become mature by the age of four or five years. In Lake Superior specifically, maturity occurs at year five. ("Minnesota Department of Natural Resources website", 2013; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

Reproduction

Male shortjaw ciscoes move to shallower waters to spawn. Shortly afterward, females migrate to the shallower waters and lay eggs for the males to fertilize. After spawning, males and females migrate back to deeper waters and abandon the eggs. ("Minnesota Department of Natural Resources website", 2013; "NatureServe Explorer: An online encyclopedia of life [web application]", 2012; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

Once they are five or six years old, shortjaw ciscoes begin spawning. This occurs during the spring or fall, although the time can vary. At this time, they move to shallower waters, about half the depth they resided in originally. Male shortjaw ciscoes are the first to move to shallower water for spawning, females migrate to the shallower water shortly thereafter. The eggs are released at the bottom of the lake and have no further parenting. During each spawning event, an average-sized shortjaw cisco can lay over 3,000 eggs. ("Minnesota Department of Natural Resources website", 2013; "NatureServe Explorer: An online encyclopedia of life [web application]", 2012; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

  • Breeding interval
    Spawning is variable for shortjaw ciscoes.
  • Breeding season
    Spawning is variable and can occur in both spring and fall.
  • Range number of offspring
    >3000 eggs laid each spawn (low)
  • Average time to independence
    0 minutes
  • Average age at sexual or reproductive maturity (female)
    5 years
  • Average age at sexual or reproductive maturity (male)
    5 years

Shortjaw ciscoes offer no parental investment. These fish lay their eggs at the bottom of the lake and abandon them immediately after. ("Species of Concern Shortjaw Cisco Status Assessment", 2012)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

Shortjaw ciscoes have an average lifespan that ranges from 10 to 13 years, where females usually live longer than males. The time span of a generation has been measured to 8 or 9 years. ("Minnesota Department of Natural Resources website", 2013; "NatureServe Explorer: An online encyclopedia of life [web application]", 2012; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

  • Typical lifespan
    Status: wild
    10 to 13 years

Behavior

Very little is known of the behavior of shortjaw ciscoes. They migrate during spawning seasons to shallower depths and also migrate during other seasons. They move from 110 to 140 m depths in the spring, to 50 to 70 m depths in the summer, and to 73 to 90 m depths during the winter. A closely related species, lake whitefish are social and always found in schools, this may be similar for shortjaw ciscoes. (Dewey, 2008; "Minnesota Department of Natural Resources website", 2013; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

Home Range

There is currently very little information available regarding the home range size of shortjaw ciscoes.

Communication and Perception

There is currently little information available regarding the communication and perception of shortjaw ciscoes. However, other members of their genus (Coregonus) such as lake whitefish are known to have the ability to perceive their environment based on olfaction. Likewise, broad whitefish have the ability to pick up sounds primarily at the low-frequency range, generally below 400 Hz. In general, members of this genus forage using their vision. Although studies have not been conducted specifically on shortjaw ciscoes, they likely have similar sensing capabilities. (Hara, 1977; Kahilainen and Ostbye, 2006; Mann, et al., 2007)

Food Habits

Shortjaw ciscoes are omnivores but most often feed on meat from opossum shrimp, the zooplankton species Pontoporeia hoyi, and insect larvae. They have also been known to feed on aquatic vegetation. ("NatureServe Explorer: An online encyclopedia of life [web application]", 2012; "Shortjaw cisco", 2008; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

Predation

Aside from being preyed on by humans, shortjaw ciscoes are highly preyed upon by invasive species like the introduced sea lamprey and native lake trout and burbots. Shortjaw ciscoes also compete for food with other introduced species like rainbow smelt and alewives. Invasive species have contributed to their population declines. (Bronte, et al., 2010; Gimenez Dixon, 1996; "Minnesota Department of Natural Resources website", 2013; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

Ecosystem Roles

Since shortjaw ciscoes feeds on opossum shrimp and zooplankton, the population decline of these fishes may cause the populations of their prey to increase. Likewise, predators of shortjaw ciscoes like sea lamprey and lake trout will also decrease or find other food sources. ("NatureServe Explorer: An online encyclopedia of life [web application]", 2012; "Shortjaw cisco", 2008; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

Economic Importance for Humans: Positive

Shortjaw ciscoes are interesting study organisms, as they hold unique ties to post-glacial hydrology. These fish are commercially caught and sold in a chub market, where they are most often prepared by smoking. ("Shortjaw cisco", 2008; "Species of Concern Shortjaw Cisco Status Assessment", 2012; Yule, et al., 2013)

  • Positive Impacts
  • food
  • research and education

Economic Importance for Humans: Negative

There are no known negative effects of shortjaw ciscoes on humans.

Conservation Status

In the 1920's, shortjaw ciscoes were the most populated deep water fish in Lake Superior, however, they currently make up about 1% of the fish population in the area. Their population decline has been impacted by over-fishing. When shortjaw ciscoes were first commercially fished, they were size selected, which caused their average size to decline. Due to commercial fishing, the species was extirpated from Lake Michigan and Lake Huron. Predation of introduced species such as sea lamprey, and competition from introduced species such as alewives and rainbow smelt, have caused their population to decline as well. Their population decline may also be due to an increase in their main predator, lake trout. Before the 1950's lake trout were heavily fished, without regulation, however, new regulations have caused an increase in lake trout populations. Due to their deep living conditions, their habitat is not expected to be at risk. However, with pollution, sediment may cover their spawning beds and restrict eggs survival. During fish surveys in Minnesota, any occurrences of shortjaw ciscoes is documented, which will help the DNR assess their population trends. No attempt has been made to manage or increase their population size through hatcheries. In Canada, they are listed as threatened. Due to their population decrease, shortjaw ciscoes are not currently commercial fished. With the increase of predation and competition of introduced species, their population size is continuing to decline. (Bronte, et al., 2010; Gimenez Dixon, 1996; "Minnesota Department of Natural Resources website", 2013; "NatureServe Explorer: An online encyclopedia of life [web application]", 2012; "Shortjaw cisco", 2008; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

Other Comments

Shortjaw ciscoes have many other common names including longjaws and paleback tullibees. (Froese, 2011)

Contributors

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

Glossary

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

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.

migratory

makes seasonal movements between breeding and wintering grounds

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.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

Minnesota Department of Natural Resources. 2013. "Minnesota Department of Natural Resources website" (On-line). Coregonus zenithicus (Jordon & Evermann, 1909). Accessed March 24, 2013 at http://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=AFCHA01140.

NatureServe. 2012. "NatureServe Explorer: An online encyclopedia of life [web application]" (On-line). Accessed March 24, 2013 at http://www.natureserve.org/explorer.

Royal Ontario Museum. 2008. "Shortjaw cisco" (On-line). Ontario's Biodiversity. Accessed March 24, 2013 at http://www.rom.on.ca/ontario/risk.php?doc_type=fact&lang=en&id=68.

U.S. Fish and Wildlife Service. 2012. "Species of Concern Shortjaw Cisco Status Assessment" (On-line). USWFS Ecological Resources. Accessed March 24, 2013 at http://www.fws.gov/midwest/eco_serv/soc/fish/sjci_sa.html.

Bronte, C., M. Hoff, O. Gorman, W. Thogmartine, P. Schneeberger, T. Todd. 2010. Decline of the Shortjaw Cisco in Lake Superior: The Role of Overfishing and Risk Extinction. American Fisheries Society, 139:3: 735-748.

Dewey, T. 2008. "Animal Diversity Web" (On-line). Coregonus clupeaformis. Accessed March 28, 2013 at http://animaldiversity.ummz.umich.edu/accounts/Coregonus_clupeaformis/#behavior.

Froese, R. 2011. "Fishbase" (On-line). Coregonus zenithicus (Jordon & Evermann, 1909). Accessed March 24, 2013 at http://www.fishbase.org/summary/Coregonus-zenithicus.html.

Gimenez Dixon, M. 1996. "Coregonus zenithicus" (On-line). IUCN Redlist of Threatened Species. Accessed March 24, 2013 at http://www.iucnredlist.org/details/5378/0.

Hara, J. 1977. Olfactory Discrimination Between Glycine and Deuterated Glycine by Fish. Experientia, 33-5: 618-619.

Kahilainen, K., K. Ostbye. 2006. Morphological Differentiation and Resource Polymorphism in Three Sympatric Whitefish Coregonus lavarctus (L.) forms in a subarctic lake. Journal of Fish Biology, 68: 63-79.

Mann, D., P. Cott, B. Hanna, A. Popper. 2007. Hearing in Eight Species of Northern Canadian Freshwater Fishes. Journal of Fish Biology, 70-1: 109-120.

Murray, L. 2006. A morphological examination of sympatric cisco forms in four lakes with specific reference to the occurrence of shortjaw cisco in Manitoba. University of Manitoba, Master Thesis: 1.

Yule, D., J. Adams, T. Hrabik, M. Vinson, Z. Woiak, T. Ahrenstorff. 2013. Use of Classification Trees to Apportion Single Echo Detections to Species: Application to the Pelagic Fish Community of Lake Superior. Fisheries Research, 140: 123-132.

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