12 



U. S. BUREAU OF FISHEEIES. 



Therefore, for several years the Bureau has had a skilled assistant 

 devote exclusive attention to the whitefishes and related species. 

 This investigation, pursued by Walter Koelz, scientific assistant, is 

 not all that is required, but it will surely provide a fund of informa- 

 tion for more intelligent guidance in future. 



The investigation of the systematic relationships and habits of the 

 coregonines was conducted in the year 1920 on Lake Michigan. 

 Forms allied to those which the investigations of the previous year 

 disclosed in Lake Huron, and in addition two undescribed species, of 

 which at least one is now known to occur also in Huron, were ob- 

 tained. Diagnoses of the species have been prepared from over 2,000 

 preserA^ed specimens. Data have been collected bearing on the dis- 

 tribution in the lake and on the spawning habits of the various forms. 

 To avoid dissemination of premature conclusions a report will not 

 be published until work is done upon other lakes. 



These studies have been supplemented by microscopic examination 

 of the scales and systematic investigation of the food, conducted, 

 respectively, by John Van Oosten and Carl L. Hubbs, temporary in- 

 vestigators, under the direction of Prof. Jacob Reighard. 



Mr. Van Oosten first determined that the scale characters of the 

 lake herring {Coregonus artedi) are so well defined as to permit the 

 determination from them of the age of individuals and the rate of 

 growth of the species. The variations in the scales of individuals 

 were found to be within specific limits. But scales from different 

 parts of the body of an individual are so unlike that for comparison 

 of individuals or species it is necessary to use scales from the same 

 body region. 



The scales of 10 specimens of each of the 10 Lake Huron forms 

 recognized by Koelz were next compared, and it was found that 8 

 of them (including the two races) are discriminable. Further study 

 will probably enable discrimination of the two other forms. It 

 appeared that in one of these forms {Coregonm artedi) there are 

 probably two geographic races which differ in rate of growth, but 

 the matter needs further study. 



Through the courtesy of Dr. C. H. Townsend, director of the New 

 York Aquarium, it was possible to secure specimens of whitefish 

 {Coregonus clupeaformis) hatched and reared at the aquarium and 

 therefore of known age (7 years). The 10 specimens studied show 

 that there is one annulus for each year of age. This, so far as known, 

 is the first demonstration of this fact and enables the determination 

 of the age of coregonine fish from scale characters to be undertaken 

 with confidence. Two individuals of the T-year-old whitefish were 

 segregated at the N^ew York Aquarium and kept living, while scales 

 were removed at intervals of a month. A study of these scales shows 

 that the annuli are formed in winter, fixes the time of formation, and 

 indicates temperature change as one of the factors. It is believed 

 that a continuation of these studies will add materially to our knowl- 

 edge of age and rate of growth of coregonine fishes, aid in their 

 systematic grouping, and lead to the discovery of local races in some 

 of the forms. 



The food of the whitefish, lake herring, and allied species of Lake 

 Huron coregonines in the Koelz collection was investigated by a 

 volumetric method by Carl L. Hubbs, of the Museum of Zoology, 



