unselected fish may be combined. Accordingly, 

 table 18, which contains average lengths and 

 weights at time of capture and coefficients of 

 condition, jC, for the males and females and for 

 the sexes combined, and table 19, which con- 

 tains calculated growth histories of the age 

 groups and grand average calculated growth, 

 have been based on all fish for which age deter- 

 minations were made. All individuals of age- 

 group I and nearly all of age -groups U, III, and 

 IV were selected whereas from 59 percent 

 (age group V) to 93 percent (age -group VII) of 

 the fish of the remaining age groups were un- 

 selected. 



The differences between lengths and 

 wei^ts of male and female yellow perch of 

 age -groups I, II, and III were small and prob- 

 ably of little significance . On the other hand, 

 lengths and weights of males and females of 

 age -groups V-VIII are indicative of a possible 

 sex difference in growth rate inasmuch as the 

 females of each age group averaged longer and 

 heavier than the males of corresponding age . 



Calculated lengths at the end of the first 

 year of life (table 19) of the various age groups 

 were in good agreement among the older age 

 groups . Calculated lengths for the first year of 

 the I -group fish were greater than those of 

 other age groups (except the single male of age- 

 group VIII) . The 12 yearling fish probably 

 represented the larger and faster growing fish 

 of their age group. Liicewise, first -year cal- 

 culated lengths of the Il-group fish tended to be 

 higher than those of the majority of the older 

 age groups, probably for the same reason. 

 Second-year calculated lengths of the Il-group 

 fish were also higher than average, which lends 

 support to the inference that these were repre- 

 sentative of only the larger, more rapidly 

 growing individuals of the age group. Inclusion 

 of age -groups I and II in the computation of the 

 general growth curve does not have a signifi- 

 cant distorting effect on the data . Among the 

 older age groups agreement of the calculated 

 lengths was satisfactory when the number of 

 specimens was adequate . 



The grand average calculated lengths at 

 the bottom of table 19 are averages of the cor- 

 responding calculated lengths of the age groups 



for the first 4 years of life . Beyond the fourth 

 year grand average calculated lengths were de- 

 termined by the successive addition of the grand 

 average increments of growth in length. This 

 procedure made possible a natural "smoothing" 

 of the growth curve in the later years. The 

 graphical representation of the general growth 

 (fig. 5) has been arranged to permit ready con- 

 versions between standard lengths in millimeters 

 and total lengths in inches. The increments of 

 growth in length are shown by broken lines . The 

 increments show that most rapid growth of both 

 sexes took place in the second year. A progres- 

 sive decline in annual growth occurred after the 

 second year, although growth of the third year 

 still exceeded that of the first. 



Calculated lengths of females of differ- 

 ent age groups were slightly larger than those 

 of males in all corresponding years of life. 

 This indication of a distinct sex difference in 

 growth rate is apparent in grand average calcu- 

 lated lengths. A similar sex difference in 

 growth rate has been found in other perch popula- 

 tions, notably in Lake Erie (Jobes, 1952). 



Length -wei^t relation and coefficient of 

 condition 



Length -weight data of Lower Red Lake 

 yellow perch are presented in table 20 and fig- 

 ure 6 for each sex and for the sexes combined. 

 In the table each length represents the average 

 of all fish in a 5 -millimeter interval of standard 

 length. The curve of figure 6 has been con- 

 structed so that it may be read in terms of 

 standard lengths in millimeters and weight in 

 grams, or fork or total length in inches and 

 weight in ounces. The length -weight data mani- 

 fested no consistently large sex differences over 

 the entire length range, althougli males of inter- 

 mediate length (172 to 198 millimeters) were 

 noticeably heavier than females of the same 

 length. 



The coefficient of condition, _K^ has been 

 calculated for the averages of length and weight 

 of fish within each 5 -millimeter interval of stand- 

 ard length (table 20) . The values of_K_of males 

 may be described as relatively low over the 

 length range of 108 to 168 millimeters, relatively 

 higfi for lengths of 172 to 2 32 millimeters, and 



42 



