LIFE HISTORY OF LAKE HERRING OF LAKE HURON 411 



GENERAL SUMMARY 



1. This paper is based on a study of the measurements, weights, and structural 

 features of the scales of 3,724 lake herring {Leucichthys ariedi Le vSucur), fishes that 

 belong to the family Coregonidse; 321 of these specimens were taken by Dr. Walter 

 Koelz in 1917 and 1919 at various ports on Lake Huron, and 3,403 were taken by 

 me in 1921, 1922, 1923, and 1924 in the region of Bay City, Mich. (Saginaw Bay), 

 and Oscoda, Mich., also ports on Lake Huron. 



2. The structural features of scales employed for life-history work are well 

 defined and easily recognized in typical coregonid scales. Li this respect these 

 scales are usable for life-history work. 



3. Scales retain their identity throughout the life of the fish. The well-estab- 

 lished facts in proof of identity are these: (a) That the nuclear area or central part of 

 the scales of old fish is structurally identical with the scales of young fish; (&) that 

 regenerated scales, which replace those accidentally lost, have a central portion of 

 quite a different type from that of normal scales; and (c) that scales increase in 

 size as long as the fish grows. 



4. In lake herring the number of scales in the lateral line is the same for both 

 sexes of an age group. 



5. In lake herring the number of scales in the lateral line is, on the average, 

 greatest in the large individuals of an age group, due to the fact that these fish were 

 also the large individuals of their year class at the time of scale formation and more 

 scales were laid down in the longitudinal rows. 



6. In lake herring the number of scales in the lateral line remains constant with 

 the year classes and with the age groups (III and older) studied. 



7. An attempt has been made to review all the criticisms that have been directed 

 against the age hypothesis and the nature and extent of all the evidences, direct and 

 indirect, that support or contradict the hypothesis. The review indicates that the 

 large majority of the experiments on the scales of fishes are fragmentary but favor, as 

 far as they go, the theory that the annuli on the scales of a fish are a reliable guide to 

 its age. This assumption has not been tested experimentally for the lake herring. I 

 have tested it, however, by experimentation for the whitefish (Coregonus clujjeaformis), 

 a coregonid closely related to the lake herring. The whitefish employed were reared 

 in the New York Aquarium and were known to be in their eighth or ninth j-ear of life. 

 (Van Oosten, 1923.) 



8. A review of the most important papers devoted to a study of the body-scale 

 growth relationship shows that the question of the validity of growth calculations 

 based on the scales of fishes is still a disputed one. The direct experimental evi- 

 dences are very fragmentary, but show, as far as they go, that calculated and empirical 

 measurements of growth agree almost exactly. An attempt has been made to ascer- 

 tain the exact growth relationship between the scales and the body of the lake herring, 

 to determine the accuracy of the calculated measurements of growth, and to analyze 

 the factors involved in the apparent discrepancies in the calculated measurements 

 of growth. 



9. In lake herring scales of the same individual may grow at different rela- 

 tive rates. 



