FISHERY BULLETIN: VOL. 83, NO. 4 



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z 



UJ 



o 



HI 



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 u. 



26 r 

 20 - 



I FETUSES 

 CALVES 



10 



70 72 74 76 78 80 82 84 86 88 90 92 94 



LENGTH (cm) 



100 r 



80 



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LU 



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60 



40 



20 



Average length 

 at birth 



I I I I I I I 



I T I t I T I I I I I I'l I I I I I 

 70 72 74 76 78 80 82 84 86 88 90 92 94 



LENGTH (cm) 



Figure 2.— Length-frequency data for specimens from sets with Itill <40 grouped in 1 cm inter- 

 vals for 163 fetuses and 221 calves from the northern offshore population of spotted dolphins, 

 and the logistic model fitted to the percentage of animals that were postnatal. 



using specimens from sets with higher levels of kill. 

 It may then be possible to determine at what level 

 of kill-per-set the estimate ceases to increase. Until 

 additional data are available, we consider 85.4 cm to 

 be the best estimate of length at birth in northern 

 offshore spotted dolphins. 



Our estimate of length at birth in the southern off- 

 shore spotted dolphin of 83.2 cm is more ques- 



tionable because we were unable to stratify by kill- 

 per-set. As adults, southern specimens are about 2.5 

 cm shorter than their northern counterparts (Per- 

 rin et al. 1979). This small, but statistically signifi- 

 cant, difference may or may not imply that length 

 at birth is smaller in the southern population. The 

 small sample of 23 specimens used in our calcula- 

 tion of length at birth raises doubts concerning the 



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