266 BULLETIN OF THE BUREAU OF FISHERIES 



PART n 



Page 



Life history of Leucichlhys artedi Le Sueur, the bkieback or lake herring 345 



Historical: A summary of our knowledge of the life history of lake herring 345 



Description of adults 345 



Natural history of adults 346 



Life liistory of adults (age and growth) 347 



Juvenile lake herring 348 



Abundance of lake herring. 349 



Interpretation of the structural features of the scales of the lake herring 349 



Material 349 



Abundance of age groups and year classes in the samples 350 



Age groups 350 



Year classes 354 



Average and extreme length and weight of herring 356 



Fish of different schools 356 



Age groups 358 



Males and females 359 



Rate of growth 361 



Method of determination 361 



Uncorrected and corrected computed lengths 362 



Growth of age groups and year classes 362 



Total lengths 362 



Increments 368 



Suggested explanation of rapid growth of young herring in 1919 in Saginaw 



Bay 370 



Law of growth compensation 370 



Norms of growth I 373 



Lengths 373 



Weights 375 



Relationship between length and weight 377 



Relative abundance of males and females 1 379 



Relative abundance of sexually immature and mature herring in the samples and 



in the general population 382 



Comparison of samples of herring taken in 1924 at the same locality in Saginaw 



Bay but on different dates 385 



Comparison of samples of herring taken in 1924 at different localities in Saginaw 



Bay 386 



Variations in rates of growth of herring from different localities in Lake Huron 388 



Factors involved in the alteration of the growth rate of Saginaw Bay herring during 



the period 1915-1923 393 



Resume of the growi h history of Saginaw Bay herring 393 



Comparison of growth rates existing before and after the period 1915 to 1918 395 



Temperature and sunshine as factors 398 



Fishing intensity as a factor 400 



Temporary chemical pollution of Saginaw Bay as a factor 403 



Indirect economic losses in herring fisheries due to chemical pollution of 1915 to 1918_- 407 



General summary 411 



Conclusions 416 



Bibliography 417 



