YELLOW PERCH OF LAKE ERIE 



245 



(1927 and 1932), however, this percentage ex- 

 ceeded 50. The proportion of undersized perch in 

 age group IV may be considered unimportant, and 

 all group-V perch were of legal size. 



The effects of the varying percentages of legal 

 and undersized yellow perch in the different age 

 groups, and of the varying abundance of the age 

 groups themselves, on the age composition of the 

 marketable catch may be seen in table 23. Age 

 group II dominated the commercial catch in all 

 years' samples except four, 1929, 1930, 1932, and 

 1945, when group-Ill fish were most numerous. 

 The data in table 23 give strong indication that 

 the time of capture within the season may have 

 an important effect on the age composition of the 

 marketable catch. The April 1932 (spawning- 

 run) sample contained no legal-sized yellow perch 

 younger than age group III. The midsummer 

 collection of 1930 (most of the fish were taken in 

 July) was dominated by age group II when both 

 legal and undersized yellow perch were included 



Table 2Z.— Distribution by age groups of legal-sized yellow 

 perch in the different years' collections from impounding 

 nets 



IPerceutages in parentheses] 



I Minimum legal size 9 inches In 1927 and 1928 and 8H Inches in all oilier 

 years. 

 ' As determined for 8M-inch limit for all years. 



(table 22). However, such a small proportion 

 (5.2 percent) of the age group had attained legal 

 size (table 22) that age group III became strongly 

 dominant (75.9 percent) when only legal-sized 

 fish were considered (table 23). Of the 10 years 

 in which all or most of the yellow perch were 

 taken in autumn (1927, 1928, 1929, 1937, 1943- 

 48), after the continued growth of group-TI perch 

 had brought a greater proportion of them to legal 

 length, this group dominated the commercial 

 catch in all but 1929 and 1945. Since the condi- 

 tions are known to have been abnormal in 1929, 

 and perhaps also in 1945, it appears vaHd to con- 

 clude that age group II normally dominates the 

 late-season commercial catch. Members of the 

 same year class dominate the fishery as age group 

 III the following spring and during the summer 

 up to the point that the growth of the incoming 

 group II makes it possible for fish of that age to 

 assume a dominant position in the commercial 

 catch. 



The conclusion about the change in the age 

 composition of the marketable catch within a 

 single season finds further support in data of the 

 1928 and 1929 collections. Scales were collected 

 in both summer and autumn of each of these 

 years. Comparisons of the percentage age com- 

 position of legal-sized perch in different months 

 of capture in the two years may be found in table 

 24. Analyses were made for the 1928 data with 

 respect to the then-effective 9-inch size limit and 

 the current 8K-inch limit. The data of table 24 

 cannot be considered descriptive of the typical 

 seasonal changes in the age composition of legal- 

 sized yellow perch since age group II was abnor- 

 mally abundant in 1928 and group III was excep- 

 tionally strong in 1929. The percentages serve, 

 nevertheless, to show clearly the tendency for 

 group II to replace group III in the marketable 

 catch as the season progresses. In 1928, age 

 group III was dominant among legal-sized j'cUow 

 perch in July (41.7 percent) but age group II 

 was dominant in the later months of the season. 

 Had an 8K-inch limit been in force, age group II 

 would have dominated the catch in July as well 

 as in late season, but its relative importance would 

 have increased, nevertheless, from 69.1 percent 

 in July to 91.1 percent in August to November. 

 The great abundance of group-Ill yellow perch 

 in 1929 made it possible for that age group to 

 maintain its dominance in the marketable catch 



