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Lake Superior longjaw

Coregonus zenithicus

What do they look like?

In the deep waters where shortjaw ciscoes thrive, they can grow to 35 cm long and weigh up to 1.0 kg. Their back is tinted olive green and their belly is white. As adults, their fins become darker, with a black tint on their pelvic and anal fins. These fish have an elliptically-shaped body. Females tend to be larger than males. These fish have large, straight snouts and 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

Where do they live?

The range of shortjaw ciscoes (Coregonus zenithicus) has become much smaller 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 found in all Great Lakes except Lake Ontario. Shortjaw ciscoes are currently found 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)

What kind of habitat do they need?

Shortjaw ciscoes are found in deep waters of large lakes, with water depth of 20 to 150 m. During the spawning season, they are found in shallower waters, in water 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)

  • These animals are found in the following types of habitat
  • freshwater
  • Aquatic Biomes
  • lakes and ponds
  • Range depth
    20 to 150 m
    65.62 to 492.13 ft

How do they grow?

Shortjaw ciscoes spawn in both the spring and fall. Young fish grow fastest during their first year of life, after which, they grow much more slowly. 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, they become mature when they are five years old. ("Minnesota Department of Natural Resources website", 2013; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

How do they reproduce?

Male shortjaw ciscoes move to shallower waters to spawn. Shortly afterward, females move to the shallower waters and lay eggs for the males to fertilize. After spawning, males and females go back to deeper waters and leave the eggs behind. ("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. Although the time can vary, these fish spawn in the spring or fall. At this time, they move to shallower waters, about half the depth they reside in normally. Male shortjaw ciscoes are the first to move to shallower water for spawning, females migrate to the shallower water shortly afterwards. 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)

  • How often does reproduction occur?
    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 do not take care of their young. These fish leave after they lay their eggs at the bottom of the lake. ("Species of Concern Shortjaw Cisco Status Assessment", 2012)

  • Parental Investment
  • no parental involvement

How long do they live?

Shortjaw ciscoes live an average of 10 to 13 years, and females usually live longer than males. ("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

How do they behave?

Very little is known of the behavior of shortjaw ciscoes. These fish migrate during spawning and 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.

How do they communicate with each other?

Very little is known about how shortjaw ciscoes sense their environment. However, other closely related fishes such as lake whitefish have a rather good sense of smell. Likewise, broad whitefish have the ability to hear mostly low-frequency sounds. Most of their close relatives also find food using their sight. Although the specific senses of shortjaw ciscoes have not been studied, they are likely similar to their close relatives. (Hara, 1977; Kahilainen and Ostbye, 2006; Mann, et al., 2007)

What do they eat?

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

What eats them and how do they avoid being eaten?

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. (Bronte, et al., 2010; Gimenez Dixon, 1996; "Minnesota Department of Natural Resources website", 2013; "Species of Concern Shortjaw Cisco Status Assessment", 2012)

What roles do they have in the ecosystem?

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)

Do they cause problems?

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

How do they interact with us?

Shortjaw ciscoes are 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)

  • Ways that people benefit from these animals:
  • food
  • research and education

Are they endangered?

In the 1920's, shortjaw ciscoes were the most common 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 fished, they were selected for their size, which caused their average size to decline. Due to commercial fishing, the species is no longer found in Lake Michigan or 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 probably not at risk. However, with pollution, sediment may cover their spawning beds and restrict eggs survival. During fish surveys in Minnesota, whenever a shortjaw cisco is seen, it is any documented. This will help the DNR assess their population trends. In Canada, they are considered threatened. Due to their population decrease, shortjaw ciscoes are no longer 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)

Some more information...

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.

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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Claypool, M. 2014. "Coregonus zenithicus" (On-line), Animal Diversity Web. Accessed January 26, 2020 at http://www.biokids.umich.edu/accounts/Coregonus_zenithicus/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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