COREGONID FISHES OF THE GREAT LAKES 



By WALTER KOELZ, Ph. D. 

 Formerly Associate Aquatic Biologist, U. S. Bureau of Fisheries 



CONTENTS 



Page 



General remarks 298 



The coregonid fishes 298 



Statement of the problem 299 



Source of material and data 299 



The Great Lakes _. 299 



Lake Nipigon 301 



Lake Superior 301 



Lake Michigan 302 



Lake Huron 302 



Lake Erie 303 



Lake Ontario 304 



Fishing methods 304 



Collection of data 304 



Localities and dates 304 



Field methods 305 



Explanation of terms and nomencla- 

 ture 305 



Glossary 305 



Measurements 305 



Counts 307 



Miscellaneous terms 308 



Systematic treatment 308 



Systematic history of the American 



coregonids 310 



Variability and determination of species 



in the Great Lakes coregonids 314 



General statement 314 



Variability of individual characters.. 315 



Body contour 315 



Length 316 



Depth and width 316 



Scales in the lateral line 317 



Scale rows 317 



Pearl organs 318 



Fins 318 



Caudal peduncle 320 



Flesh 320 



Color 321 



Vertebrae 321 



Page 



General remarks — Continued. 



Variability and determination of species 

 in the Great Lakes coregonids — 

 Continued. 

 Variability of individual characters — 

 Continued. 



Pyloric caeca 322 



Head form 322 



Brain box 324 



Premaxillaries 324 



Snout 324 



Maxillary 324 



Mandible 325 



Eye 325 



Teeth 326 



Branchiostegal membrane and 



rays 326 



Gill rakers 326 



Nares 326 



Discussion of variability 328 



Interspecific variations 328 



Intraspecific variations 328 



Speciation in the Great Lakes core- 

 gonids 331 



Origin of the coregonids in the basin. 331 

 Physiological barriers between the 



species 333 



Segregation through different hab- 

 itat selection 333 



Segregation through different 



breeding habits 334 



Acknowledgments 334 



Species of Coregonidae in the Great Lakes. 335 



Analyses of the species 335 



Lake Nipigon 335 



Lake Superior 336 



Lake Michigan 337 



Lake Huron 338 



Lake Erie 339 



Lake Ontario 339> 



297 



