PERRIN ET AL.: STOMACH CONTENTS OF PORPOISE AND YELLOWFIN TUNA 



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mains; stomachs with traces are those contain- 

 ing only squid beaks and fish otoliths and/or 

 skeletal fragments. The volumetric analyses 

 are based on the full stomachs only. The number 

 and occurrence analyses are based on the full 

 stomachs and those with traces. In addition to 

 the material collected from simultaneous 

 catches of two or more of the three predator 

 species, fish otoliths were examined from an- 

 other 5 spotted porpoise and 14 spinner por- 

 poise captured with yellowfin tuna in various 

 locations in the eastern tropical Pacific (Ap- 

 pendix Tables 1 and 2). 



RESULTS 



Haul 1 



Only the two species of porpoise were sampled 

 in Haul 1 (Table 2). The results for the species 

 are sharply divergent. For the spotted porpoise, 

 cephalopods predominated in volume, numbers, 

 and occurrence. Onychoteuthid, ommastrephid, 

 and enoploteuthid squids were the major food 

 items. Fish made up an insignificant proportion 

 of the volume and consisted primarily of the 

 epipelagic 0.njp(>rha)>iphus niicropteriis. In the 

 four spinner porpoise examined, squid and fish 

 were present in all the stomachs, each account- 

 ing for about half the total volume. The species 

 composition of the squid component of spinner 

 stomachs was different from that in the spotted 

 porpoise mainly in that one of the unidentified 

 ommastrephids (type B, probably Sijniplecto- 

 teuthis sp.) was completely absent, whereas it 

 was present in 27 of the 29 spotted porpoise. 

 Fish, primarily myctophids, predominated in 

 numbers, the ratio of fish to squid being almost 

 precisely the reverse of that for the spotted por- 

 poise. Five myctophid species were present in 

 all four stomachs. By far the commonest fish 

 was Diogenichthys sp. (probably laternatus). 

 A bregmacerotid, Bregmaceros sp., was also 

 found in all four stomachs and was the next 

 most common fish, followed closely by the me- 

 lamphaid Scopelogadus bispinosus and the 

 myctophid La mpanyctus parvicauda. 



Haul 2 



All three species were examined in Haul 2 

 (Table 3). The results for the spotted porpoise 



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