YELLOW PERCH OF LAKE ERIE 



229 



fish averaged the larger. There is a striking 

 similarity in the growth curves of the other three 

 populations (fig. 6). The yellow perch from Lake 

 of the Woods averaged about 1 inch longer than 

 those from Green Bay and northwestern Lake 

 Michigan at the end of the first year, and after 

 this year the individuals from northwestern Lake 

 Michigan averaged somewhat shorter than those 

 from the other two areas. 



Although each of these growth rates compares 

 favorably with those from other waters, slow 



growth does occur in the Great Lakes. Van 

 Oosten (1944) reported a sample of yellow perch 

 taken from Presque Isle Bay (Lake Erie) that 

 averaged only 6.7 inches total length as age-group- 

 IV fish. Apparently these slow-growing fish do 

 not frequent Lake Erie proper as none was found 

 among the thousands examined in the course of 

 the present study. The largest yellow perch taken 

 from Lake Ontario by Greeley (1940) had a total 

 length of just more than 6.5 inches in its fifth 

 summer of life. 



GROWTH COMPENSATION 



Two types of relation between early size and 

 subsequent growth have been observed: (1) That 

 in which the individuals with greater growth in the 

 first year retain or add to that advantage in later 

 growth; and (2) that in which the individuals with 

 greater growth in the first year grow relatively 

 more slowly each subsequent year so that a reduc- 

 tion in range of size occurs. This latter relation 

 is known as growth compensation. No attempt 

 will be made to review the literature on the subject, 

 but it may be stated that the phenomenon of 

 growth compensation has been observed in so 

 many species of fish, both marine and fresh-water, 

 that its occurrence may be considered general. 



Age groups II and III of the 1929 collection, 

 both of which contained large numbers of speci- 

 mens, have been selected for a study of the rela- 

 tion between the first-year length and the later 

 growth in length of the Lake Erie yellow perch. 

 The data have been restricted further to those 

 fish collected late in the autumn, when it could be 

 assumed that the year's growth was complete. 

 Table 10 shows the growth histories of the dif- 

 ferent yearling-size classes (sexes separately) of 

 each of these age groups. 



The first-year difference of 0.99 inch between 

 the average lengths of the largest and smallest 

 group-II males was increased to 1.38 inches in the 

 second year. The maximum difference was re- 

 duced by compensatory growth in the third year 

 to 1.05 inches, but nevertheless remained above 

 the original difference. In the group-II females 

 the original 0.94-inch advantage of the largest 

 yearlings over the smallest was increased sfightly 

 to 0.97 inch in the second year. The maximum 

 difference was reduced by compensatory growth 

 in the third year to only 0.68 inch. 



Table 10. — Relation between calculated length of Lake Erie 

 yellow perch at end of first year and growth in subsequent 

 years, based on 1929 collections of age groups II and III 



The relation between first-year length and later 

 growth in length of both sexes of age group III 

 resembled that of the group-II males. The 

 largest yearlings of both the males and females 

 added materially to their first-year advantage 

 over the smallest j-earlings during the second year 

 of fife. The maximum difiference was reduced by 

 compensatory growth during the third year, but 

 remained greater than the original difference. In 



