M8 



Fishery Bulletin 89(3). 1991 



100 



90 



< 70 



*k 60 



012>(156)('7e)(,92)('31>(107) 



UJ 



CD 



50 



O 30 

 CC 



10 

 



70 120 130 140 150 160 170 



BODY LENGTH (cm) 



□ 



falcate 





erect 



canted 



Figure 8 



Change in percentage of males (top) and females (bottom) from 

 "whitebelly"-type schools with canted (Code 1), erect (Code 

 2), and falcate (Code 3) dorsal fins in relation to body length. 

 Sample sizes in parentheses. 



In the "whitebelly" schools (Fig. 8), roughly 90% of 

 calves, juveniles, and adult females had falcate dorsal 

 fins and about 10% erect fins. One adult female had 

 a canted fin. In adult males, the frequency of erect fins 

 increased to about 40% in individuals of 175 cm or more 

 (2.3% had canted fins). Again, this is about the length 

 at attainment of sexual maturity (he. cit.). We limited 

 the analyses of dorsal fin shape in the pooled samples 

 to sexually mature dolphins and considered males and 

 females separately. 



We followed the same procedure for analyses of body 

 length, limiting the sample to sexually mature animals 

 and analyzing males and females separately. 



Effects of seasonal variation The apparent overlap 

 of collection localities for the two kinds of schools is 

 not an artifact of seasonal migrations. The region of 

 substantive overlap of "eastern" and "whitebelly" 



schools is between 8° and 12°N and 95° and 125°W 

 (Fig. 3). We examined the data by quarter of the year 

 and found overlap in this region in all four quarters. 



Pooling to obtain adequate sample sizes Sample 

 sizes in many cases were very small for some of the 

 peripheral 5-degree blocks. In these cases we pooled 

 the samples over two or more blocks, to achieve a 

 minimum sample size of 25. In the pooling we at- 

 tempted to approximate the apparent radial pattern 

 of variation, i.e., pooling was mainly longitudinal in the 

 south and mainly latitudinal in the west. To the extent 

 possible, we maintained the same pooling scheme from 

 analysis to analysis, although in some cases differen- 

 tial pooling was required for males and females. The 

 sample sizes and pooling schemes for the various 

 analyses are given in the Appendix. 



