STRUHSAKER and UCfflYAMA: AGE AND GROWTH OF STOLEPHORUS PURPUREUS 



150 

 140 

 130 

 120 

 110 



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MAY 9, 1972 



33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 

 STANDARD LENGTH (mm ) 



Figure 2. — Stolephorus purpureus: First holding experiment. 



170 

 160 

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 140 



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100 

 90 

 80 



JANUARY 26, 1973 



JANUARY 19, 1973 



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34 36 38 40 42 44 46 48 50 52 54 56 58 



STANDARD LENGTH (mm) 



Figure 3. — Stolephorus purpureas: Second holding experiment. 



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 160 

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MAY 25,1973 



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JUNE 8,1973 



46 47 48 49 50 51 52 53 54 55 56 57 58 

 STANDARD LENGTH (mm) 



Figure 4. — Stolephorus purpureus: Third holding experiment. 



growth rate has increased in the captive popula- 

 tion after 34 days in captivity, but has not reached 

 the value of the wild population from which it was 

 taken. 



In the first holding experiment, the second and 

 third samples were collected 16 and 34 days, re- 

 spectively, after the initial sample. For unadjust- 

 edy values, these samples differed from the initial 



sample by 16.2 and 33.2 increments, whereas for 

 the adjusted y values, they differed from the 

 initial sample by 13.9 and 29.7 increments 

 (Table 1). 



The results of the two samples (collected after 

 more than 30 days in captivity) collected 19 and 26 

 January 1973, and compared in the second hold- 

 ing experiment, are summarized in Table 1 and 

 Figure 3. There were no significant diff'erences 

 between the means of the independent variables 

 or the regression coefficients at theP ssO.OS level. 

 The elevations of the two regression curves are 

 significantly different at theP ^0.001 level. The 

 differences in number of increments between 

 unadjusted y values (6.0) and adjusted y values 

 (7.6) again closely approximate the expected dif- 

 ference of 7 days between samples. 



The results of the samples of 25 May and 8 June 

 1973 compared from the third holding experiment 

 are given in Table 1 and Figure 4. In this experi- 

 ment there was a significant difference between 

 the means of the independent variable (P <0.001), 

 but no differences between the regression coef- 

 ficients and elevations of the two regression 

 curves at theP «0.05 level. The significant differ- 

 ence in mean length between the two samples is 

 probably attributable to the increased amount of 

 food provided to the captive population and the 

 resulting high growth rate exhibited throughout 

 the duration of the experiment. Because the 

 treatment significantly affected the independent 

 variable, further examination of the regression 

 statistics is unwarranted. However, if the two 

 samples are subjected to a two-group comparison, 

 there is a significant difference between the mean 

 number of increments for each sample (P <0.05). 

 The difference between the means for each sample 

 (25 May,y = 124.9; 8 June, J = 140.0) closely ap- 

 proximates the expected difference of 14 days be- 

 tween samples. 



We conclude from the relatively good agree- 

 ment between the increase in mean number of 

 growth increments and the number of days be- 

 tween collection of samples, that these data from 

 the holding experiments provide direct evidence 

 of the presence of daily growth increments in the 

 sagittae of nehu. 



Growth of Sagittae 



The total lengths of sagittae from the 5 April 

 and 9 May 1972 nehu samples (the initial sample 

 from the wild population and the 34-day sample) 



13 



