Updating 1220 cisco

27-Jul-2015 21:50 by 8 Comments

Updating 1220 cisco - cross dating

The chub fishery had nothing to do with the various cyprinid fish species known as chubs but was exclusively based on the various species of ciscoes.The fishery continued as cisco stocks fell and non-native species such as sea lamprey, rainbow smelt and alewife spread through the system and increased in abundance.

The fishery shifted focus from species to species as cisco numbers declined and has been largely defunct for some years.

The ranges of the three cisco species above extend across Beringia to the Asian coasts.

Of those the Arctic cisco and least cisco (=sardine cisco) are widespread through northern Siberia.

In the inland waters of northern Europe, the European cisco or vendace (Coregonus albula) replaces the Siberian sardine cisco.

The ciscoes (or ciscos) are salmonid fish of the genus Coregonus that differ from other members of the genus in having upper and lower jaws of approximately equal length and high gill raker counts.

These species have been the focus of much study recently, as researchers have sought to determine the relationships among species that appear to have evolved very recently.

The term cisco is also specifically used of the North American species Coregonus artedi, also known as lake herring.

In previous taxonomic classifications, the ciscoes have been identified as a subgenus Leucichthys of the genus Coregonus.

Based on molecular data this is not a natural classification however, as the ciscoes are polyphyletic, comprising two different lineages within the freshwater whitefishes.

Usually, several taxa of ciscoes are found in a single lake. According to genetic analyses, these cisco types do not represent unique, separate evolutionary lineages, but similar cisco morphs have evolved and attained their specific characteristics largely independently in each lake.

They exhibit different habitat distributions, feeding and breeding habits and morphological adaptations e.g. Therefore it has been suggested that they should not be recognized formally as distinct taxa, but all considered members of a single species, Coregonus artedi (sensu lato).

Ciscoes have been exploited in commercial fisheries, particularly in the Laurentian Great Lakes where the deepwater forms were the basis of the so-called chub fishery.

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