PREY OCCURRENCE IN PANTROPICAL SPOTTED DOLPHINS, STENELLA-ATTENUATA, FROM THE EASTERN TROPICAL PACIFIC

Identified prey of pan-tropical spotted dolphins, Stenella attenuata, include 56 species of fish and 36 species of cephalopods. Species iden tifications were made from fish otoliths and cephalopod beaks recovere d from 428 stomachs collected throughout the eastern tropical Pacific between 1989 and 1991. The most frequently found fish were lanternfish (family Myctophidae) at 40%, and the most frequently found cephalopod s were flying squids (family Ommastrephidae) at 65%. The dominance of these primarily mesopelagic prey species and a significantly higher st omach fullness index for stomachs collected during the morning hours ( chi(2)=112.99, df=6, P<0.0001) suggest that pantropical spotted dolphi ns feed at night when many mesopelagic species migrate toward the surf ace. Significant differences in prey composition by season and geograp hic region indicate that pantropical spotted dolphins are flexible in their diet and may be opportunistic feeders. Comparison of the diets o f pregnant and lactating female dolphins revealed that lactating femal es increase both the proportion of squid in their diet and quantity of food consumed.