YELLOW PERCH OF LAKE ERIE 



241 



Table 18. — Length frequencies of Lake Erie yellow perch taken in different types of gear 



[Collections of all years combined] 



' Each H-inch interval contains lengths up to but not including the greater value. 

 > Specimens occurred in the samples but made up less than 0.005 percent of the total. 



a tabulation desirable sLnce legal-size limits for 

 yellow perch are expressed in terms of the total 

 length in inches. It may be seen at a glance, for 

 example, that with a size limit of 8K inches, 55.6 

 percent of the yellow perch taken in trap nets were 

 under legal length, whereas 79.38 percent were 

 undersized with a 9-inch limit; or it may be seen 

 that almost 98 percent of the yellow perch in trap- 

 net catches were less than 10 inches long. The 

 tabulation also permits ready comparisons of the 

 catches by different types of gear. 



The length distributions by age for impounding- 

 net samples are shown in table 19. The collections 

 of 1930, 1932, and 1937 are omitted from the table 

 because the number of specimens whose ages were 

 determined was too small in each of those years 

 to give reliable results. The length range of fish 

 of the same age did not vary greatly in the better- 

 represented age groups during the 3 years 1927 to 

 1929. The range in length of the age groups was 

 sufficiently great to cause considerable overlapping 

 between these groups. Because of this overlap, 

 length cannot be held a reliable indication of age. 

 Age groups IV and V were represented by too few 

 individuals to give an accurate idea of the range 

 in either group. The distinctly unimodal dis- 

 tribution within each well-represented age group 

 and the great amount of overlapping in length 

 probably accounted for the unimodal length dis- 



tribution in the yearly collections from impounding 

 nets. 



Additional data obtained from impounding nets 

 each year in the period 1944^8 (table 20) make 

 possible a comparison of the length distribution 

 of the legal-sized yeUow perch in the commercial 

 catch of those years with the legal-sized fish in- 

 cluded in the biological samples collected from 

 the same type of nets in the 3 years 1927 to 1929. 

 Only age groups II and III will be compared since 

 younger and older fish contributed but little to 

 the commercial catch. 



The length distribution of the legal-sized (8^ 

 inches total length and larger) yellow perch 

 assigned to age group II exhibited a striking dif- 

 ference between the two periods, 1927-29 and 

 1944-48. The minimum legal size of 8% inches 

 was near, or above, the modal length of aU group-II 

 fish in each of the 3 years 1927 to 1929. The 

 length distribution of group-II fish in each year 

 of the period 1944-48 gave strong reason to be- 

 lieve that the 8K-inch size limit was below (less 

 than) the modal length each year with the pos- 

 sible exception of 1945 when the small sample 

 agreed more nearly with the data of the earUer 

 period. Also in each year except 1945 of the 

 recent period, age group II contained longer fish 

 than in any year of the earlier period. Fmlher, 

 the number of the longer group-II fish tended to 



