YELLOW PERCH OF LAKE ERIE 



237 



Table 17. — Length frequencies of Lake Erie yellow perch by year of capture and type of gear 

 [An asterisk designates tbe modal interval in each frequency distribution] 



' Gill nets 22 meshes deep. 



quency group in each gear. The modal frequency 

 intervals of perch caught in impounding nets 

 varied from 161-170 mm. (7.6 inches total length) 

 in 1928 and 1930 to 191-200 mm. (9.0 inches 

 total length) in 1929, or over a range of 30 mm. 

 (1.4 inches). Annual fluctuations in the per- 

 centage occurrence of individuals in the several 

 length intervals of the trap-net and pound-net 

 catches of 1927-29, inclusive, are showTi graphi- 

 cally in figure 8, which includes only the length 

 range over which the representation was continu- 

 ous. The years 1927 to 1929 were selected for 

 graphic presentation because the year class of 1926 

 dominated the collections for each of those three 

 years. The mode of the 1927 specimens caught in 

 impounding nets was at a length 10 mm. greater 

 than the mode of the 1928 collections. Since col- 

 lections of both years were dominated by fish of the 

 1926 year class, one would expect the length of the 

 modal frequency in 1928 to be greater than that in 

 1927. However, this discrepancy can be ex- 

 plained readily. It may be seen in table 21 that 

 two age groups were well represented in the 1927 

 icollections ; age group I made up 48.9 percent and 

 age group II made up 39.9 percent of the total. 

 The 1928 collections were made up almost entirely 

 (90.6 percent) of group-II fish. Approximately 



> Oill nets 100 meshes deep. 



95 percent of the 1927 specimens were taken in 

 October and November whereas some 72 percent 

 of the 1928 individuals were taken by the end of 

 June. Thus, the 1926 year class (group I of 1927), 

 had only a small part of a growing season in which 

 to increase their lengths before the 1928 collections 

 (in which the year class appeared as age group II) 

 were made. Furthermore, the occurrence of large 

 munbers of group-II fish m 1927 caused the length 

 at maximum abundance in the combined collec- 

 tions of that year to be greater than that of the 

 dominant age group (see table 19). Thus, the 

 reduced abundance of fish older than the 1926 

 year class in 1928 and the short period of time 

 Lutervening between the dates of collection of the 

 1927 and 1928 samples no doubt account for the 

 shorter modal length in 1928. 



The large modal length in 1929 may be attrib- 

 uted in great measure to the dominant 1926 year 

 class which had completed approximately 2 full 

 years' growth subsequent to the collection of the 

 1927 material. Even so, the length of the modal 

 frequency in 1929 was somewhat less than the 

 modal length of the 1926 year class (age group III) 

 in that year because of the strong representation 

 of the 1927 year class (age group II). In general, 

 the position of the modal frequency each year can 



