FISHERY BULLETIN: VOL. 70, NO. 4 



important contributors by volume were Gonosto- 

 matidae, 44.7%; Engraulidae, 8.99f ; Mullidae, 

 7.9%; Gempylidae, 2.7%; Serranidae, 2.5%; 

 Lutjanidae, 2.0%; Scombridae, 1.6% ; Carangi- 

 dae, 1.6%; and Priacanthidae, 1.5%. Important 

 contributors by volume to the diet of yellowfin 

 tuna were Gonostomatidae, 22.1%; Mullidae, 

 14.8%; Tetragonuridae, 6.3%; Carangidae, 

 3.8%; Paralepididae, 1.5%; Priacanthidae, 

 1.2%; and Scombridae, 1.0%. The remaining 

 fish families contributed less than 1% per fam- 

 ily for both species of tunas. The high volumet- 

 ric contribution by the family Tetragonuridae 

 was due to the large size of only four Tetrago- 

 nurus cuvieri, which were found in a single 

 stomach of a yellowfin tuna. 



During UN6802 most important fish families 

 by volume and by frequency of occurrence were 

 Carangidae, Gempylidae, Paralepididae, Scom- 

 bridae, and Trichiuridae. Serranidae and Scor- 

 paenidae were prominent in the diet of skip- 

 jack tuna, but entirely absent in the diet of 

 yellowfin tuna. Important contributors by vol- 

 ume in the diet of skipjack tuna were Paralep- 

 ididae, 28.4%; Percoidei, 8.6%; Carangidae, 

 3.1%; Serranidae, 1.5%; Trichiuridae, 1.4%; 

 Gempylidae, 1.3%; and Scombridae, 1.2%. In 

 the diet of yellowfin tuna important contributors 

 by volume were Exocoetidae, 9.6% ; Alepisauri- 

 dae, 5.6%; Carangidae, 2.7%; TrachyiDteridae, 

 2.6%; Scombridae, 2.5%; and Percoidei, 1.4%. 

 The remaining fish families and suborders in 

 the diet of both species of tunas contributed less 

 than 1 % per taxon in terms of volume. The rel- 

 atively high contribution by the families Exo- 

 coetidae and Alepisauridae was due to the large 

 volumes of only three forage fish (Appendix 

 Table 4). From our data we see that some of 

 the prominent forage fish families for both spe- 

 cies of tunas were common to both cruises and 

 that others were important during only one 

 cruise (Appendix Tables 1-4). 



CRUSTACEANS 



As shown in previous publications (Drago- 

 vich, 1969, 1970), crustaceans, because of their 

 high numbers and high frequency of occurrence, 

 were important components of tuna food. Crus- 



taceans found in tuna stomachs during both 

 cruises were similar. The majority were larval 

 stomatopods, hyperiid amphipods, and different 

 types of megalopae or their equivalents. The 

 highest number (32) of taxa was noted in the 

 diet of skipjack tuna during UN6801, while in 

 the diet of yellowfin tuna for the same cruise, 

 20 different taxa were identified — 16 of these 

 were common in the diet af both species of tunas. 

 During UN6802, 22 different taxa were identi- 

 fied in the diet of skipjack tuna and 10 in the 

 diet of yellowfin tuna — 7 were common to both 

 species of tuna. Stomatopods were not iden- 

 tified further than order. Phronima sedentaria, 

 Phrosina semUimata, and Brachyscelhis spp. 

 were the most common amphipods in both tunas 

 for both cruises. Megalopal stages probably con- 

 sisted of many species, but due to the lack of 

 taxonomic literature, they were not identified 

 further than class or family. 



A variety of anomurans and caridean shrimp 

 were consumed by both species of tunas. Dar- 

 danus pectinatus (Glaucothoe) was the most im- 

 portant anomuran for both tunas during both 

 cruises. Carideans were more prominent during 

 UN6801 than during UN6802. 



Euphausia hanseni was eaten by both tunas 

 during UN6801. During UN6802, E. hanseni 

 occurred in high numbers in the diet of skipjack 

 tuna but was entirely absent in the food of yel- 

 lowfin tuna. Since E. hanseni are of minute 

 size, they were probably accidentally ingested 

 or the skipjack tuna were filter feeding. The 

 same explanation may be applied to other or- 

 ganisms of similar size found in the stomachs 

 of both species of tunas, for example, copepods 

 and isopods. Another explanation is that some 

 of the euphausiids, copepods, or isopods could be 

 the remains of stomach contents of other fishes 

 ingested by tunas. 



Phyllosoma occurred in low numbers in the 

 diet of both species during both cruises. The 

 identified forms were Panulirus rissoni, Scyl- 

 larus arctus, Scyllariis sp., and Scyllaridea sp. 



MOLLUSKS 



Cephalopods formed the bulk of the molluscan 

 food of both species of tunas during both cruises. 



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