The kiyi (''Coregonus kiyi'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

freshwater whitefish The freshwater whitefish are fishes of the subfamily Coregoninae, which contains whitefishes (both freshwater and anadromous) and ciscoes, and is one of three subfamilies in the salmon family Salmonidae. Apart from the subfamily Coregoninae, th ...

, a deepwater

cisco Cisco Systems, Inc., commonly known as Cisco, is an American-based multinational digital communications technology conglomerate corporation headquartered in San Jose, California. Cisco develops, manufactures, and sells networking hardware, ...

, endemic to the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lak ...

of North America. It previously inhabited

Lake Superior Lake Superior in central North America is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. and the third-largest by volume, holding 10% of the world's surface fresh wa ...

, Lake Michigan, Lake Huron and

Lake Ontario Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York. The Canada–United States border ...

, but is now believed to persist only in Lake Superior where it is common. The various deepwater ciscos are also called chubs (not to be confused with the various species of Cyprinidae also called chubs). The kiyi is part of the large group of related northern ciscos known as the ''Coregonus artedi'' complex.

Description

The kiyi is one of the smaller ciscos. Adult kiyi average approximately in

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

and in weight. Individuals can reach more than . They are silvery pink or purple iridescence, darker on the back and white on the belly. They may have a dark tip on the lower jaw. They have a large head and a conspicuous, large eye.

Subspecies

Two subspecies of kiyi have been recognised based on morphological characteristics and distribution. The nominate subspecies ''Coregonus kiyi kiyi'', or the Upper Great Lakes kiyi, was found in Lakes Superior, Huron and Michigan. The Lake Ontario kiyi, ''C. kiyi orientalis'', was only found in Lake Ontario. However, recent examination of the ciscos as a group using genetic techniques has suggested that some recognized species are not genetically distinct from others, and it has been suggested that the deepwater ciscos in general may be forms of the northern cisco ''C. artedi'' adapted to life in different ecological niches. The distinction between the subspecies of kiyi has been rendered academic, however, by the extinction of the Lake Ontario form, which has not been seen since the 1960s and has been extinct since 2005. The subspecies was driven to extinction by commercial exploitation, predation and competition by introduced species.

Ecology and behavior

The kiyi is reportedly most abundant at depths greater than over its range, with Lake Superior kiyi said to be abundant at depths of . Females are known to grow larger and live longer (10 years) than males (8 years). Age at maturity is believed to be 2 to 3 years. The minimum size at maturity is reported as in Lake Superior. Spawning takes place in autumn or early winter, and has been reported in depths of . Ciscoes are known to exhibit large fluctuations in reproductive success and will produce several years of strong year classes followed by several years of poor reproductive success. Although not the preferred chub species owing to their relatively small size, kiyi were a substantial component of the Great Lakes chub fisheries at one time, particularly in Lake Ontario. They, along with other deepwater chubs, have been negatively affected by a combination of factors, including the invasion of the Great Lakes by several non-native species that prey on various life stages of the chubs or compete with them. Parasitic

sea lamprey The sea lamprey (''Petromyzon marinus'') is a parasitic lamprey native to the Northern Hemisphere. It is sometimes referred to as the "vampire fish". Description The sea lamprey has an eel-like body without paired fins. Its mouth is jawless, ...

(''Petromyzon marinus'', alewife (''Alosa pseudoharengus'') and

rainbow smelt The rainbow smelt (''Osmerus mordax'') is a North American species of fish of the family Osmeridae. Walleye, trout, and other larger fish prey on these smelt. The rainbow smelt prefer juvenile ciscoes, zooplankton such as calanoid copepods ('' L ...

(''Osmerus mordax''), in particular, have been implicated in their demise, and are believed to have stressed populations to the extent that previously sustainable levels of exploitation became unsustainable.

References

*COSEWIC (2005
COSEWIC assessment and update status report on the Lake Ontario kiyi ''Coregonus kiyi orientalis'' and Upper Great Lakes kiyi ''Coregonus kiyi kiyi'' in Canada.
Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 17 pp. * * {{Taxonbar, from=Q3756635 Coregonus Fish described in 1921 Taxa named by Walter Koelz