246 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 24. — Percentage age composition of legal-sized yel- 

 low perch in Lake Erie in different months of capture in 

 1928 and 1929 



to the end of the season. The representation of 

 age group II increased, however, from 0.8 percent 

 in July to 14.4 percent in August and September 

 and to 31.6 percent in November and December. 

 At the same time the corresponding percentage 

 representations of age group III changed from 

 85.5 to 85.6 to 59.4. 



The legal-sized fish of the combined samples for 

 all years' collections belonged very largely (92.1 

 percent) to age groups II and III which were 

 represented almost equally — 46.1 and 46 percent 

 (table 23). However, the relatively high repre- 

 sentation of age group III can be traced to the 

 large 1929 collection in which it was dominant. 

 A more reliable estimate of the age composition 

 of the marketable catch may be had from the un- 

 weighted averages of the percentages for the 

 different years. At the bottom of table 23 these 

 averages are given as computed from the size 

 Hmits actually in effect in the different years (that 

 is, from a size limit of 9 inches in 1927 and 1928 

 and of SK inches in the later years) and as com- 

 puted from a size Hmit of 8K inches for all years. 

 The percentages computed from both the effective 

 and the 8K-inch size Umits showed dominance of 

 age group II. 



Yellow perch older than age group V were not 

 found in the samples, but are known to have been 

 present in Lake Erie. Specimens selected because 

 of their large size revealed no males older than 

 age group IV, but did include one female of age 

 group VII and two fish of undetermined sex 

 assigned to age group VIII. 



The data on the age composition of gill-net 

 catches (shoal and bull nets) contained in tables 

 25, 26, and 27 correspond to those already given 



for trap nets. The data for 1927 and 1928 in- 

 cluded both legal- and iUegal-sized fish while 

 those for later years' represented only the com- 

 mercial sizes. Comparisons between the catches 

 of trap nets and giU nets bring out sharply the 

 strongly selective action of the latter gear. Age 

 group III dominated three of the four gill-net 

 collections obtained in 1927 and 1928 (table 25). 

 The fourth (the bull-net collection of 1928) was 

 dominated by age group II, but age group III was 

 only slightly less abundant. This distribution of 

 the age groups bears Uttle resemblance to the age 

 composition of the less-selective impounding nets 

 (table 21) where the 1927 samples were dominated 

 by age group I (48.9 percent), and 90.6 percent of 

 the yellow perch in the 1928 collections were 

 members of age group II. The 1927 gill-net 

 samples do not give the sUghtest indication of the 

 great abundance of age group I. Possibly the 

 dominance of age group II in the 1928 buU-net 

 collection was due to the great abundance of 

 group-II fish in that year. However, the shoal- 

 net collection failed to reveal such dominance and 

 abundance. On the whole, the age composition 

 of gill-net catches appears to be in large measure 

 independent of the relative strength of the age 

 groups in the population. Characteristically, age 

 group III was dominant, with age group II regu- 

 larly well represented and occasionally dominant. 

 The tendency for giU nets to take older fish than 

 do trap nets may be seen also in the greater abun- 

 dance of group-IV yellow perch in the gill-net 

 samples. 



A second difference between gUl-net and im- 

 pounding-net collections lies in the greater pro- 

 portion of legal-sized yellow perch in the age groups 

 from the former gear (table 26). For example, 

 the percentages of legal yellow perch of group II, 

 in the impounding-net collections for 1927 and 

 1928, were only 15.1 and 12.4, computed from a 

 9-inch size hmit (table 22). Group II in the gill- 

 net collections for these years, on the other hand, 

 contained from 30.2 to 79.2 percent of such perch 

 and showed an average for the 2-year period (bull 

 and shoal nets combined) of 47.9 percent. If the 

 percentages of legal-sized yellow perch in age 

 group II are computed from a size limit of 8K 

 inches, the values are 39.7 for impounding-net 

 samples and 76.3 for gill-net collections. A 

 similar though less pronounced difference existed 

 between the percentages of group III legal-sized 



