FOOD OF YELLOW FIN TUNA IN THE CENTRAL PACIFIC 



By John W. Reintjes and Joseph E. King 

 Fishery Research Biologists 



The Pacific Oceanic Fishery Investigations of 

 the United States Fish and Wildlife Service is 

 authorized 1 and directed to gather information 

 to ensure maximum development and use of the 

 high-seas fishery resources of the territories and 

 island possessions of the United States in the tropi- 

 cal and subtropical Pacific. Since the tunas con- 

 stitute the group of pelagic fishes having the larg- 

 est and most immediate economic potential in 

 this region, research has been concentrated on 

 species of this group. 



In view of the recognized importance of food 

 as an environmental factor influencing the dis- 

 tribution of fish, a study was initiated to determine 

 what tunas eat, and how the abundance and dis- 

 tribution of food organisms are related to the 

 abundance and distribution of tunas. The first 

 part of the study has been accomplished with a 

 reasonable degree of completeness for the yellow- 

 fin tuna, Neothunnus macropterus (Temminck 

 and Schlegel), and the results are presented in this 

 report. Further study of the abundance and 

 distribution of tuna is needed. 



The yellowfin tuna occurs in all parts of the 

 tropical Pacific. In recent years it has constituted 

 50 to 60 percent of the catch of the live-bait tuna 

 fishery of the west coasts of the Americas. The 

 longline fishery in the vicinity of the Hawaiian 

 Islands depended on the yellowfin for more than 

 50 percent of its catch in the years 1945-48 (June 

 1950). The species also comprises about 50 

 percent of the catch of the Japanese longline 

 fishery in the tropical western Pacific. It is taken 

 by native peoples and sport fishermen throughout 

 its range. 



The literature contains many references to the 

 food of yellowfin. Most of these, however, are 

 based on casual observations made on small 

 samples of fish, or refer to material regurgitated 

 by the fish when it was landed. Observations 

 by the following authors are worthy of mention. 



1 Public Law 329, 80th Congress. 



Kishinouye (1917, 1923), reporting on the food 

 of yellowfin captured by longline fishing in the 

 Bonin Islands, stated that they feed on flyingfish, 

 "coffer fish," "some deep-sea fish," "calamaries," 

 pteropods, heteropods, hyperid amphipods, larval 

 and immature Squilla, and the megalops of crabs. 

 Okuma, Imaizumi, and Maki (1935) noted that 

 large amounts of small skipjack, shrimp, small 

 crabs, carangids, and balistids were found in 

 yellowfin stomachs collected in Indo-Pacific waters. 

 Nakamura (1936, 1943), from an examination of 

 the stomach contents of yellowfin captured by 

 longline gear in the Celebes Sea, reported clupeoid, 

 scombroid, and plectognath fishes among the most 

 common food items, followed by squid and palinu- 

 rids, squillids, syllarids, and Leander among the 

 crustaceans. 



Walford (1937) reported that flyingfish, sauries, 

 sardines, squid, and larval and adult planktonic 

 crustaceans were found in the stomachs of yellow- 

 fin captured by surface fishing in the coastal 

 waters of the eastern Pacific. Marukawa (1939) 

 examined 12 longline-caught yellowfin from equa- 

 torial waters south of the Palaus, and briefly 

 summarized the results in a checklist which 

 includes fishes, squid, and crustaceans. Kana- 

 mura and Yazaki (1940a, 1940b) found squid, 

 triggerfish, balloonfish, and shrimp in the stomachs 

 of longline-caught yellowfin from the East Philip- 

 pine Sea and the South China Sea. Ban (1941) 

 reported the occurrence of planktonic animals, 

 paper nautilus, trunkfish, juvenile carangids, 

 mackerel, sphyraenids, and mature skipjack 

 among the stomach contents of yellowfin. Ikebe 

 (1942) stated that yellowfin captured in waters 

 southwest of New Guinea were feeding mostly on 

 squid. Suyehiro (1942) reported briefly on the 

 stomach contents of a "sample" taken during one 

 day's fishing off southern Japan. In addition to 

 his own observation he reported that leatherfish, 

 cuttlefish, and shrimp were found in the stomachs 

 of yellowfin taken near Timor Island. 



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