TELLOW PERCH OF LAKE ERIE 



259 



respect to condition would not be expected lo 

 operate on these accidental captures. The selec- 

 tion by gill nets of yellow perch according to the 

 condition of the fish is similar to the action of drift 

 (gill) nets on marine herring (Farran 1936) and 

 supports the i)revious conclusion of a like action 

 among the smaller perch by impounding nets. 



From the preceding discussion it appears not 

 only that gill nets tenfl to take relatively heavier 

 yellow perch in Lake Erie than trap nets but that 

 in gill-net samples K decreased with increases in 

 length. The resulting distortion of the data 

 justifies the exclusion of gill-net material from the 

 study of condition. 



SIZE AT MATURITY 



A knowledge of size at sexual maturity has its 

 practical application in the determination of the 

 minimum legal size that may be needed to protect 

 an adequate spawning stock. Data on the rela- 

 tion between total length and the percentage of 

 maturity of the yellow perch taken in 1927-37 are 

 given for the sexes separately and combined in 

 table 36. The males matured at a much smaller 

 size than the females: 47.4 percent of the males 

 were mature or maturing at 6 to 6.5 inches and 

 48.4 percent of the females were mature or matur- 

 ing at 8 to 8.5 inches. Any minimum legal size for 

 the Lake Erie yellow perch, therefore, must be 

 based on the maturity of females. 



The shortest K-inch total-length interval that 

 contained a large percentage of mature females 

 was 8 to 8.5 inches. At that length 48.4 percent 

 were mature. At lengths of 8.5 to 9 inches 86.1 

 percent were mature, and at 9 to 9.5 inches 97 per- 

 cent were mature. All females 9.5 inches and 

 longer were mature. These data show that 86.1 

 percent of the females were mature in the shortest 

 }2-inch total-length interval (8.5 to 9) available to 

 the commercial fishery operating under the 8}2-inch 

 minimum legal size now effective in the Michigan 

 and Ohio waters of Lake Erie (no size limit on 

 yellow perch in Pennsylvania and New York 



waters). The samples collected in 1947-48 showed 

 an even greater proportion of mature female yellow 

 perch since 51 of 53 individuals (96.2 percent) in 

 the 8.5- to- 9-inch interval were mature. 



On the basis of the data in table 36 it is ap- 

 parejit that the great majority of female j'ellow 

 perch in Lake Ya'ip mature at total lengths 

 between 8 and 9 inches. Reference to table 19 

 reveals that most of the fish with these lengths 

 belonged to age group II (174 mm. standard 

 length is equivalent to 8 inches total length, and 

 196 mm. equals 9 inches). It thereby becomes 

 apparent that the majority of the female yellow 

 perch reach maturity in Lake Erie during their 

 third year of life and spawn for the first time early 

 in theii- fourth year (as age-group-III fish). The 

 average calcidated length of the females at the 

 end of the third year of life was 8.6 inches 

 (table 7). 



Although the data in tables 36 and 19 are from 

 fish taken late in the fall one would expect little, 

 if any, growth in winter or until spawTiing time 

 in the spring. The percentages of maturity at 

 the different sizes determined from fall samples, 

 therefore, may be applied reasonably well to the 

 spawning-season population. The small sample 



Table 36. — Relation between length of Lake Erie yellow perch and proportion of mature individuals, 1927-37 



> Fish included within each total-length and fork-length interval had lengths equal to the lowest and up to. but not including, Che greatest length of the 



interval. 



