GREAT LAKES COREGONIDS 



305 



many thousand pounds of fish were seen and examined, and a total of about 15,000 

 specimens was collected. These are mostly catalogued and preserved in the Museum 

 of Zoology of the University of Michigan at Ann Arbor. 



Field Methods 



In the field it was my practice to be present when the nets were being lifted. 

 In the case of the whitefish usually it was possible then to examine nearly every 

 fish taken in the lift; but in the case of Leucichthys the individuals of a catch were 

 far more numerous, so that it was possible to examine only samples of the catch. 

 In any case these samples seldom comprised less than one-tenth of the catch and 

 often (in the case of lifts under 1,000 pounds in weight) constituted half or more. 

 The results of these examinations are given as applicable to the whole catch. 



In addition to actual specimens, stomachs were collected also, chiefly on Lake 

 Huron. These have been examined by Dr. Carl L. Hubbs, of the Museum of 

 Zoology, University of Michigan, and his report is given under the heading "Food" 

 for Lake Huron species. 



At first fish were measured in the field, but as these measurements, of necessity, 

 were made under such adverse conditions that it was not possible to check them, 

 the practice was discontinued. Records of fish companies and log books of fisher- 

 men showing the weight and the locations of catches were copied wherever they 

 could be obtained conveniently, and from every port the accounts of the habits of 

 the various species of coregonids were recorded as given by the fishermen. Informa- 

 tion of this kind has been secured through correspondence, also. 



As a result of all the field work adequate material was made available on which to 

 base conclusions regarding the systematic status of the various forms that occur in the 

 Great Lakes. These conclusions from the study of specimens are supported by the 

 accumulated field data dealing with the geographical and bathymetric distribution 

 of these forms in the lakes, with their breeding grounds, breeding seasons, and their 

 food. 



EXPLANATION OF TERMS AND NOMENCLATURE 



GLOSSARY 

 Measurements 



All specimens collected were examined or reexamined in the laboratory. All 

 measurements were made with fine dividers, calipers, a steel tape, and a wooden 

 rule gauged in millimeters. The percentages and proportions used in the text 

 or in the tables were arrived at by arithmetical calculation. The form of expressing 

 the range of values is an arbitrary one. The usual values of a series given between 

 the figures in parentheses (which are the extremes) represent, roughly, two-thirds of 

 the individuals in that series. No series was subjected to statistical treatment 

 because the number of individuals in none is adequate for refined analysis. All 

 parts were measured and counted on the left side wherever possible. The method 

 of making the measurements, the actual points from which measurements were 

 made, and the symbols by which the measurements are designated in the tables 

 and in Figure 8 are given below: 



Length (L). — Measured from the junction of the premaxillaries to the end of the 

 last vertebra. If the specimen was distorted, it was returned as nearly as possible to 



