LIFE HISTORY OF LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 



By Stanford H. Smith, Fishery Research Biologist 



The lake herring, or shallowwater cisco, Leu- 

 cichthys artedi (LeSueur) , occurs in all of the Great 

 Lakes and in many inland lakes of the St. Law- 

 rence, Hudson River, and upper Mississippi River 

 drainages (Hubbs and Lagler, 1949), and has 

 rather general distribution throughout Canada 

 and Alaska in lakes and some rivers, and in 

 Hudson and James Bays (Dymond 1933, 1943, and 

 1947). Close relatives of the lake herring have a 

 circumpolar distribution in the glaciated areas of 

 the Northern Hemisphere. 



The lake herring is a member of the family 

 Coregonidae, a complex and not well understood 

 group of fish. Much confusion resulted from 

 early attempts to describe tliis group in the Great 

 Lakes (see Koelz 1929; pp. 311-314). The dis- 

 agreement stemmed botli from the fact that early 

 workers studied only small numbers of specimens 

 from one or a few localities and from the high 

 degree of individual and geographic variability in 

 size, shape, and taxonomic counts that charac- 

 terizes this group. Koelz made a comprehensive 

 ta.xonomic study of coregonids inhabiting the 

 Great Lakes and Lake Nipigon based on about 

 15,000 specimens from many parts of each lake. 

 He recognized the high degree of variabihty in the 

 group and was able to organize the confused 

 taxonomy. What had been described as several 

 species by comparisons of a few specimens often 

 were found to be representatives of a single species 

 that varied greatly in form over its range. Koelz 

 recognized the different species inhabiting the 

 several lakes and thus established a system of 

 nomenclature which has since been adequate for 

 the species of the Great Lakes. He recognized all 

 coregonids of the Great Lakes as belonging to the 

 family Coregonidae and the genera Coregonus 

 (Artedi) Linnaeus, Leucichthys Dybowski, and 

 Prosopium Mihier that had been described from 

 studies of coregonids over their entire range. 



A few authors have deviated recently from the 

 system of classification used by Koelz and have 

 placed Leucichthys and Prosopium in the genus 

 Coregonus. I prefer to retain Leucichthys as a 

 genus because it represents a well-defined group in 

 North America. The Leucichthys group in Europe 

 is ascribed to the subgenus Aryyrosomus; however, 

 European workers have written me that these fish 

 are distinct from other coregonids of that continent. 



The consolidation of all groups under the single 

 genus Coregonus disregards the recognizable 

 divergence of the phyletic lines represented by the 

 three genera. It is true that the high degree of 

 morphological plasticity characteristic of the 

 coregonids sometimes causes morphometric and 

 even gross appearances to approximate or, in 

 isolated instances, to overlap each other. This 

 superficial parallelism may occasionally hide the 

 distinctness of the groups, but it cannot overrule 

 the primary genetic divergence that is so clearly 

 shown by the distributional pattern of each group. 



For each genus there is a central range where its 

 members are highly variable {Coregonus in Europe, 

 Prosopium in northwestern North America, Leuci- 

 chthys in northeastern North America), and where 

 they are usually divided into several spe«?s7" 

 Range extensions of each group are characterized 

 by lesser morphological variability and at the 

 extremes only one or two relatively stable species 

 remain. Ambient morphological divergences in 

 isolated populations of one group may in some 

 instances parallel developments common among 

 members of another group and thereby tend to 

 obscure the distinctness of the groups. Such 

 occurrences cannot, however, be interpreted as 

 incomplete separation of the groups. 1 believe 

 the separate genera describe these phyletic lines in 

 the clearest and most useful manner and shoidd 

 be retained in keeping with this basic purpose of 

 modern taxonomy. 



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