YELLOW PERCH IN SAGINAW BAY 



391 



Table 31. — Calculated total lengths (inches) and length 

 increments of male and female yellow perch of Saginaw 

 Bay in different years of life 



[Data from tables 26 and 27] 



1 See caption of table 29. 



the samples). This difference in growth rate 

 between male and female fish affected the age at 

 which the legal size (8*4 inches) was reached. 

 The male perch took 6 years to reach this legal 

 size and the female more than 4i/ 2 years. 



The greatest increase in length for both sexes 

 took place during the first year of life (2.6 inches 

 for the males and 2.7 inches for the females). 

 The amount of growth dropped sharply during 

 the second year (1.6 inches for both sexes). The 

 decrease continued for the males through the 

 seventh year but the females made nearly the 

 same amount of growth every year (1.3 inches 

 to 1.6 inches) through the sixth year of life. 

 After the sixth year annual growth increments 

 dropped continuously. 



A divergence of growth curves of the sexes 

 surely is characteristic of the yellow perch and 

 may be of the perch family. It has been ob- 

 served in the three Great Lakes stocks of perch 

 that have been studied and was reported for the 

 Saginaw Bay walleye by Hile (1954). 



Annual fluctuation of growth in length 



Data on the annual fluctuation of growth in 

 length of Saginaw Bay yellow perch (tables 32 

 and 33) are so arranged as to facilitate the com- 

 parison of the growth increments. The growth 

 in a particular year of life in the different calen- 

 dar years can be read from the horizontal rows. 

 The columns show the increments for the different 

 years of life in a particular calendar year. The 

 growth histories of individual age groups can be 

 traced from the diagonal rows. Records are 

 given separately by sex and age because of sex 

 differences in growth and systematic discrepancies 

 among calculated lengths of fish of different ages. 

 Age groups represented by fewer than 10 fish 

 have been omitted from the tables. 



It is readily apparent from tables 32 and 33 

 that growth increased or decreased sharply in 

 some years, whereas for other years no trend can 

 be detected. A comparison of the growth of 

 males in 1945 and 1946, for example, reveals a 

 consistent increase of the increments from 1945 

 to 1946 for all the years of life for the different 

 age groups (table 32). On the other hand, the 



Table 32. — Annual increments of growth in length of male Saginaw Bay yellow perch, spawning-run collections of 1943-55 



[Each diagonal gives the growth history of an age group, belonging to the year class Indicated by the year of lst-year growth and captured in the sprine of the 

 calendar year following the one for which the last increment Is given. Number of fish in sample of each age group in parentheses immediately below lst- 

 year Increment] 



