CONTENTS 



Page 



Introduction 365 



Materials and methods 366 



sllection of samples 366 



f ecords for individual fish 366 



etermination of age 366 



Preparation and examination of scales 366 



Age analysis 367 



Commercial fishery for yellow perch 368 



General trends of the fishery, 1891-1955 368 



Catch by gear 370 



Seasonal distribution of the catch 370 



Age composition and year-class strength 371 



Annual and seasonal differences of age distribution 371 



Relative strength of year classes 374 



Size at capture 377 



Length distribution of samples 377 



Length distribution of age groups 378 



(Jhange in length between 1929-30 and 1943-55 379 



Lengm- weight relation 380 



(Seneral length-weight relation 381 



Weight in relation to condition of gonads 382 



Seasonal change in weight 382 



Comparison with length- weight relation in 1929-30 and with other Great 



Lakes populations 383 



Calculated growth 384 



Body-scale relation 384 



Key scales below the lateral line 384 



Key scales above the lateral line 386 



Comparison of length calculated from different scales of the same fish 386 



Implications as to procedure in calculation of growth 387 



Growth in length 387 



Growth in length of age groups 387 



General growth rate 390 



Annual fluctuation of growth in lengths 391 



Fluctuations in first-year growth 392 



Fluctuation in growth in later years of life 393 



Growth in weight , 394 



Growth in weight of the age groups: general growth 394 



Annual fluctuation of growth in weight 396 



Difference in growth rate in 1929-30 and 1943-55 and comparison with growth 



from other Great Lakes waters 398 



Probable factors of the decrease in growth rate 400 



Possible factors of fluctuations in year-class strength and growth rate 404 



Environmental factors and fluctuation in year-class strength 405 



Environmental factors and fluctuation in growth rate 406 



First-year growth 406 



Growth in later years of life 407 



Sex and maturity 408 



Size at maturity 408 



Sex ratio 409 



Sex ratio of individual samples 409 



Change of sex ratio with increase in age 410 



Sum mary 411 



Literature cited 413 



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