416 



Fishery Bulletin 89(3), 1991 



EASTERN 



WHITEBELLY 



EASTERN 



WHITEBELLY 



 SO" 1*0" 1»* 120" HO" 



SO" SO' TO" no- 





Figure 4 (continued) 



of the characters were recorded for all of the specimens 

 (Table 1). Body-length data were available for 3304 

 adult dolphins (1461 males and 1843 females). (Females 

 with at least one ovarian corpus and males with testis/ 

 epididymis weight of lOOg or more were considered 

 adult, following Perrin et al. 1977.) 



Analytical methods 



Area! stratification For purposes of the analyses, we 

 divided the study area into 60 5-degree blocks with 

 boundaries at the Equator, 5 degrees, 10 degrees, etc., 

 and 80 degrees, 85 degrees, etc. We experimented with 

 4-degree blocks and with different placement of the 

 boundaries but obtained less consistent results (more 

 embedded and peripheral anomalous blocks) than with 

 the scheme adopted. 



Effects of sexual dimorphism and development 



Color pattern and fin shape are known to vary with 



sex or age or both (Perrin 1972). We endeavored to 

 take into account these factors in the geographical 

 analyses by considering males and females separately 

 where necessary and by applying a minimum length 

 or sexual-maturity criterion for specimens to be in- 

 cluded in analyses of each of the characters separately. 



