Kiyi
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| Coregonus kiyi (Koelz, 1921) |
The kiyi (Coregonus kiyi) is a deepwater cisco or chub (not to be confused with the various species of Cyprinidae called chubs), endemic to the Laurentian Great Lakes. It inhabited Lakes Superior, Michigan, Huron and Ontario but is now believed to persist only in Lake Superior where it is common. It is reportedly most abundant at depths greater than 80 m over its range, with Lake Superior kiyi said to be abundant at depths of 180 m.
This is one of the smaller ciscoes. Adult kiyi average approximately 250 mm total length and 170 grams in weight. Individuals can reach more than 280mm. 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 conspicuous, large eye.
Two subspecies have been recognised based on morphological characteristics. The nominate subspecies Coregonus kiyi kiyi was found in Lakes Superior, Huron and Michigan. Lake Ontario was home to C. kiyi orientalis. However, recent examination of the ciscoes as a group using genetic techniques has suggested that some recognized species are not genetically distinct form others, and it has been suggested that the deewater 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.
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 132 mm in Lake Superior. Spawning takes place in autumn or early winter, and has been reported in depths of 106-165 m. Ciscos 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 (Petromyzon marinus, alewife (Alosa pseudoharengus) and rainbow smelt (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.
[edit] References
- "Coregonus kiyi". FishBase. Ed. Ranier Froese and Daniel Pauly. October 2004 version. N.p.: FishBase, 2004.
- Coregonus kiyi (TSN 161945). Integrated Taxonomic Information System. Accessed on 23 October 2006.
