458 



Fishery Bulletin 92(2). 1994 



of the dispersal of schools outside the nominal range 

 used in calculating the abundance estimate. The 

 center of distribution of spotted and eastern spin- 

 ner dolphins is the warm tropical surface water in 

 the core of the ETP. Therefore, the apparent re- 

 sponses of the two populations to environmental 

 variability are similar. 



The different effects of environmental variability 

 on the habitats of the three stocks of common dol- 



phins appear to complicate the response of the popu- 

 lation as a whole. Data collected during surveys of 

 the central and northern stocks of common dolphins 

 in fall 1992 and 1993, respectively, will allow us to 

 quantify stock-specific habitats and, perhaps, re- 

 sponses to environmental variability. We detected no 

 effect of environmental variability on the abundance 

 estimates of whitebelly spinner dolphins, but the 

 CCA results inadequately define the geographical 



