Paul Vecsei Owen T. Gorman Daniel L. Yule Thomas C. Pratt Nicholas E. Mandrak David B. Bunnell Andrew M. Muir Randy L. Eshenroder 2016 <p>This study of the ciscoes (<i>Coregonus</i>, subgenus <i>Leucichthys</i>) of the Great Lakes and Lake Nipigon represents a furtherance through 2015 of field research initiated by Walter Koelz in 1917 and continued by Stanford Smith in the mid-1900s—a period spanning nearly a century. Like Koelz’s study, this work contains information on taxonomy, geographical distribution, ecology, and status of species (here considered forms). Of the seven currently recognized forms (<i>C. artedi</i>, <i>C. hoyi</i>, <i>C. johannae</i>, <i>C. kiyi</i>, <i>C. nigripinnis</i>, <i>C. reighardi</i>, and <i>C. zenithicus</i>) described by Koelz as major in his 1929 monograph, two (<i>C. johannae</i> and <i>C. reighardi</i>) are extinct. In addition, <i>C. alpenae</i>, described by Koelz but subsequently synonymized with <i>C. zenithicus</i>, although extinct, is recognized as valid making a total of eight major forms. Six of these forms, all but <i>C. artedi</i> and <i>C. hoyi</i>, have been lost from Lake Michigan, and seven have been lost from Lake Huron, leaving in Lake Huron only <i>C. artedi</i> and an introgressed deepwater form that we term a hybrid swarm. <i>C. artedi</i> appears, like its sister form <i>C. alpenae</i>, to have been lost from Lake Erie. Only <i>C. artedi</i> remains extant in Lake Ontario, its three sister forms (<i>C. hoyi</i>, <i>C. kiyi</i>, and <i>C. reighardi</i>) having disappeared long ago.</p><p>Lakes Superior and Nipigon have retained their original species flocks consisting of four forms each: <i>C. artedi</i>, <i>C. hoyi</i>, and <i>C. zenithicus</i> in both lakes; <i>C. kiyi</i> in Lake Superior; and <i>C. nigripinnis</i> in Lake Nipigon. Morphological deviations from the morphotypes described by Koelz have been modest in contemporary samples. Overall, <i>C. kiyi</i> and <i>C. artedi</i> were the most morphologically stable forms while <i>C. hoyi</i>, <i>C. nigripinnis</i>, and <i>C. zenithicus</i> were the least stable. Although contemporary populations of <i>C. artedi</i> from Lakes Michigan and Huron are highly diverged from the morphotypes described by Koelz, the contemporary samples were of undescribed deep-bodied forms unlikely to have been sampled by Koelz because of their association with bays. Of the two intact species flocks, Lake Nipigon’s was much less stable morphologically than Lake Superior’s even though Lake Nipigon is far less disturbed. Two priorities for research are determining the role of developmental plasticity in morphological divergence, especially within <i>C. zenithicus</i> of Lake Superior, and the basis for morphological divergence in <i>C. artedi</i>.</p> application/pdf en Great Lakes Fishery Commission Ciscoes (<i>Coregonus</i>, subgenus <i>Leucichthys</i>) of the Laurentian Great Lakes and Lake Nipigon reports