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FISHERY BULLETIN: VOL. 74, NO. 2 

 126 



•I 



90 100 110 120 130 140 150 160 170 



BODY LENGTH (cm) 



80 



190 



200 210 



Figure 23. — Scatterplot of weight of both ovaries on body length in Stenella attenuata. Open dots represent females with a 

 corpus luteum. For animals 160 cm or longer, where sample for 5-cm interval is 10 or more, means (circled symbols) and ranges 

 are graphed and points are not plotted. Where the sample is &30, ± two standard errors are indicated by bars. 



conception are the best of the four and probably 

 bracket the true values. Under method number 3, 

 age hypotheses numbers II and III are more prob- 

 ably correct than number I. Accordingly, we esti- 

 mate that sexual maturity is, on the average, at- 

 tained at 181 ± 1 cm and 9.0 (8.6 to 9.3) layers (5.1 

 to 8.3 yr, depending on the alternative layering 

 hypothesis used). 



An increase in size of Graafian follicles is 

 another criterion of approaching sexual maturity. 

 Diameter of the largest follicle also shows a sharp 

 increase after 160 cm total length (Figure 25), con- 



250 



current wdth the increase in ovary weight (Figure 

 23). The largest follicle in immature females usu- 

 ally is less than 1 mm in diameter. The largest 

 follicles in most ovaries containing scars are be- 

 tween 1 and 8 mm in diameter, but a few follicles 

 (possibly cystic) as large as 10 to 16 mm in diame- 

 ter were encountered. 



Ovarian Changes in Adults 



The analyses of ovarian changes are based on 

 material collected through 1972. The corpus 



