YELLOW PERCH OF LAKE ERIE 



227 



Table 8. — Average calculated weight, by age, of Lake Erie 

 yellow perch 



(Collections of all years combined] 



Year of life 



Males: 



1 year.. 



2 years.. 



3 year... 



4 year.. 



5 year.., 



6 year.. 

 Females: 



1 year... 



2 year.. 



3 year... 



4 year.. 



5 year.. 



6 year.. 

 All fish: 



1 year.. 



2 year.. 



3 year.. 



4 year.. 



5 year.. 



6 year.. 



Weight 



Qrams 



8 



66 



113 



160 



204 



59 

 125 

 190 

 246 

 303 



58 

 119 

 172 

 224 



279 



Ounces 



0.28 

 1.98 

 3.99 

 5.64 

 7.20 



.32 



2.08 

 4.41 

 6.70 

 8.68 

 10.69 



.32 

 2.05 

 4.20 

 6.07 

 7.90 

 9.84 



Increment 

 in weight 



Ouncei 

 0.28 



1.70 

 2.01 

 1.65 

 1.66 



.32 

 1.76 

 2.33 

 2.29 

 1.98 

 2.01 



.32 

 1.73 

 2.16 

 1.87 

 1.83 

 1.94 



Increase 



607.1 

 101.5 

 41.4 

 27.7 



650.0 

 112.0 

 61.9 

 29.6 

 23.2 



640.6 

 104.9 

 44.5 

 30.1 

 24.6 



Erie perch (see p. 252) has been employed to com- 

 pute weights corresponding to the grand-average 

 lengths of table 7. These calculated weights are 

 table 8 which shows also the annual 



given in 



increments and percents of increase in weight. 

 The data on general growth in weight are pre- 

 sented graphically in figure 5. 



The calculated weights of the females exceeded 

 those of the males in every year of life. The 

 advantage of the females increased regularly from 

 0.04 ounce at the end of the first year of fife to 

 1.48 ounces at the end of the fifth. The greatest 

 advantage in the growth of the females occurred 

 in the fourth year of life when the increment was 

 2.29 ounces as compared to 1.65 for the males. 



For each sex and for the sexes combined the 

 annual percent increase in weight was greatest 

 in the second year and decreased continuously in 

 the later years. The greatest actual increase in 

 weight occurred in the third year of life. At the 

 end of the third year, when the Lake Erie yellow 

 perch attained the legal length, 8^ inches, the 

 weight (4.2 ounces) was less than half that at the 

 end of the sixth year (9.8 ounces). The heaviest 

 male weighed 12)4 ounces and the heaviest female 

 (a gravid specimen) weighed 19% ounces. 



GROWTH OF YELLOW PERCH IN LAKE ERIE COMPARED WITH THAT IN OTHER 



WATERS 



Comparison of the growth of yellow perch hi 

 Lake Erie with that in other waters will be based 

 on data from the major centers of commercial 

 production of the species. With reference to other 

 waters, it is sufficient to say that the numerous 

 published average lengths of the age groups show 

 tremendous variation in the size of fish of the same 

 age. There appears to be no correlation between 

 geographical location of the lakes and the rate of 

 growth of perch. 



Table 9 gives the average calculated total length 

 of yellow perch at the end of each year of life as 

 determined in the present study; ' by Hile and 

 Jobes for Saginaw Bay (1941) and for the Wis- 

 consin waters of Green Bay and northwestern 

 Lake Michigan (1942); and by Carlander (1942) 

 for the Mimiesota waters of Lake of the Woods. 

 The data are presented graphically in figure 6. 

 The total lengths shoA^ii were determined where 



' Data on the Lake Erie yellow perch published by Harkness (1922) are 

 not Included in the table because of differences In criteria for recognizing 

 aimuli, and his estimated lengths were not computed with reference to the 

 end of years of life. Study of these scales, which he kindly sent to me, failed 

 to reveal any pronounced differences In the rates of growth of yellow perch 

 collected by him in 1920 and of those collected In 1927 and used in the present 

 study. 



necessary from standard lengths in millimeters by 

 use of the appropriate conversion factors. Calcu- 

 lated lengths at the end of each year of life are 

 used rather than length of the age groups at 

 capture to eliminate discrepancies caused by differ- 

 ences in the time of capture. 



With the single exception of the first year when 

 the growth from Lake of the Woods was the 

 greatest (3.9 inches), the yellow perch were 

 larger in Lake Erie and Saginaw Bay than in the 

 other three areas. The Lake Erie yellow perch 

 were larger than those from Saginaw Bay in the 

 first 3 years of life. In the fourth year they aver- 

 aged the same, but thereafter the Saginaw Bay 



Table 9. — Comparison of average calculated total lengths of 

 yellow perch from several localities 



[Data for sexes combined) 



955513— 52- 



