124 



Fishery Bulletin 88(1), 1990 



r =0.88 p <0.001 



000 005 010 015 



Post-anal Hump Depth (/TL) 



Figure 7 



Canting Index vs. postanal hump liejith for male Dali's porpoise 

 specimens. Dashed box comprises juvenile and immature males. 



of overlap for all age/sex classes, except mature males 

 (Fig. 5c). There was no significant difference in this 

 feature between sexes in immatures (t = 1.683, df = 26, 

 p>0.05), but the difference between mature males and 

 females was highly significant (f = 14.935, df = 56, 

 p<0.001). The caudal peduncle only becomes greatly 



deepened in adult males, and again this appears to be 

 an absolute difference. Peduncle depth represents 

 >15% of the total length in mature males, and <15% 

 in all other age/sex classes. 



Size of thoracic epaxial muscle mass There was a 

 noticeable "hump" on the back of most adult males ex- 

 amined in this study (Fig. 8f). Dissections of this hump 

 revealed that it resulted from an increase in the size 

 of the thoracic epaxial muscle mass. It did not seem 

 to be asociated with an increase in the thickness of the 

 blubber layer. 



Measurement of the thoracic girth in Dali's porpoise 

 was not a good indication of the size of this muscle 

 mass. There was no difference in the size of the thoracic 

 girth (relative to total length) either between immature 

 males and females {t =0.245, df = 26, p>0.05) or be- 

 tween mature males and females (^=0.130, df = 56, 

 /;>(}. 05) (Fig. 5d). After an increase in thoracic girth 

 from the neonate to the juvenile stage, it leveled off 

 in both sexes. 



Flul<e shape Although no quantitative data were col- 

 lected on this aspect ol' Dali's porpoise morphology. 



Figure 8 



Ball's porpoise age/sex classes: (a) calf (TAJ 171), (li) juvenile female (TA.l 09.3). {<■) immature female (TAJ liVZ). (d) immature male (TAJ 

 1(58). (e) mature female (TAJ 145), (f) mature male (TAJ 150). 



