Northern cisco
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| Coregonus artedi Lesueur, 1818 |
The northern cisco (Coregonus artedi), also known as lake herring and tullibee, is a species of fish in the salmon family (Salmonidae).
This species occasionally grows as large as 400 mm and 5 pounds (2.3 kg) but is more commonly 280 to 380 mm long and 170 to 907 grams (six ounces to two pounds) in weight. It is slender-bodied and silvery with pinkish iridescence on its sides.
It is a pelagic fish occurring in the midwater zone of cold water lakes in North America. In the northern and western parts of its range it is also found in large rivers.
Diet is predominantly zooplankton and insect larvae, although fish eggs and larvae, icluding those of their own species are also documented. Small fish, icluding some minnow species, are also known to be consumed at times.
Northern cisco are preyed upon by a wide variety of predatory species, and have a particularly important place in the diet of lake trout (Salvelinus namaycush). It is also a common food of rainbow trout (Oncorhynchus gairdneri), northern pike (Esox lucius), burbot (Lota lota), yellow perch , (Perca flavescens) and walleye (Sander vitreum) where the species overlap ranges.
The abundance of northern cisco in the Laurentian Great Lakes is much reduced from the levels of the 19th Century. Once abundant in all five lakes, it is now common in only Lake Superior. The Lake Huron population has been increasing recently, perhaps as a consequence of low alewife (Alosa pseudoharengus) abundance. Limited numbers have also reappeared in Lake Michigan's lower Green Bay. Numbers in Lakes Erie and Ontario remain far below historical levels. The reduced abundance is believed to result from the cumulative effects of several factors, including the expansion of non-native species such as alewife, rainbow smelt(Osmerus mordax) and sea lamprey (Petromyzon marinus). These species prey on and compete with various life stages of northern cisco. It is unclear what effect the annual stocking of several million non-native Pacific salmon in the Great Lakes has had on northern cisco.
As well, substantial environmental degradation in some parts of the range has undoubtedly contributed to the stresses on northern cisco populations. The populations are therefore believed to be more vulnerable to the effects of exploitation than previously, even at levels of harvest lower than what was once sustainable.
Northern cisco are fished commercially and for sport. In the early years of the fishery, herring provided some of the largest catches from the Great Lakes and, when salted down or smoked for preservation, provisioned much of the surrounding territory. Northern cisco roe is also valued on the international market.
[edit] The "Coregonus artedi" species complex
The northern cisco is one of several closely related North American species. The group is the subject of considerable debate about the taxonomic relationships of different forms, and it has been credibly argued that the species described in this entry is merely one form of a larger species that includes all or some of species such as blackfin cisco and shortjaw cisco. These species are often referred to as the "Coregonus artedi" complex (including the quotation marks).
[edit] References
- "Coregonus artedi". FishBase. Ed. Ranier Froese and Daniel Pauly. October 2004 version. N.p.: FishBase, 2004.
- Coregonus artedi (TSN 623384). Integrated Taxonomic Information System. Accessed on 12 December 2004.
