YELLOW PERCH IN SAGINAW BAY 



379 



Table 16. — Length-frequency distribution of spawning-run collections of Saginaw Bay yellow -perch, 1943-55, according to 



age groups and sex 



in age group III to 6 inches in age group VI. 

 The widest ranges were mostly confined to age 

 groups IV, V, and VI. The younger and older 

 age groups (groups II, III, and VII) had the 

 narrower range (in part, probably, because of the 

 limited numbers of fish and for the young fish 

 the inability of the nets to hold the smaller mem- 

 bers of the age groups). 



This range of length of age groups together 

 with the distinctly slow growth led to an exten- 

 sive overlap. Consequently the length of Sagi- 

 naw Bay yellow perch at these ages is a poor 

 index of age. A fish of a particular length 

 might belong to 2 to 5 age groups (mostly 4 age 

 groups). 



The percentage of legal-sized yellow perch was 

 nil or small at the lesser ages but increased with 

 growth. In well-represented groups (age groups 

 IV, V, and VI), the percentage (sexes combined) 

 ranged from 7.9 to 56.8 percent. These three age 

 groups are the main contributors to the commer- 

 cial yellow perch fishery in Saginaw Bay. The 

 percentage of legal-sized males was always less 

 than that of the females. For males the value 

 ranged from 1.8 percent for fish of age group IV 

 to 54.5 percent in age group VII. The percent- 

 age of legal-sized females, on the other hand, rose 

 from 14.0 percent in age group IV to 100 percent 

 in age group VII. 



Change in Length Between 1929-30 and 1943-55 



The length-frequency distributions of spring 

 collections of yellow perch from impounding nets 

 in 1929-30 and 1943-55 (table 17; fig. 9) indi- 

 cate an enormous shift in the length composition. 

 In 1929-30 the modal length was at 8.5-8.9 

 inches, whereas in 1943—55 this mode was 6.5—6.9 

 inches, a loss of 2 inches in the modal length of 

 the fish (2.3 inches in the mean length). In the 



Table 17. — Length-frequency distribution of the early- 

 season collections of Saginaw Bay yellow perch, 1929-30 

 and 1943-55 



' Data 



adapted from table 7, Hile and Jobes (1941). 



