FOOD OF TUNAS AND DOLPHINS (PISCES: SCOMBRIDAE AND 



CORYPHAENIDAE) WITH EMPHASIS ON THE DISTRIBUTION AND 



BIOLOGY OF THEIR PREY STOLEPHORUS BUCCANEERI (ENGRAULIDAE) 



Thomas S. Hida' 



ABSTRACT 



The results of examining the stomach contents of skipjack tuna (Katsuwonus pelamis), 

 bigeye tuna (T/iMnnMS ofeesMs), yellowfin tuna (Thunnus albacares) ,ka-wa.ka\va (Euthyn- 

 mis af finis) , common dolphin (Coryphaena hippxtnis) , and the little dolphin (Coryphaena 

 equiselis) caught by live bait pole-and-line fishing and trolling in the equatorial eastern 

 Pacific and around the Samoa Islands are presented. Fishes, crustaceans, and molluscs 

 were found to be important food items. The presence of the anchovy, Stolephorus 

 buccaneeri^ among the stomach contents was of particular interest, and information 

 gained on their distribution, size frequency, fecundity, and food habits is presented. 



This report is based mainly on observations 

 and stomach sample collections that were made 

 during Charles H. Gilbert cruise 116 to the equa- 

 torial eastern Pacific in October-November 1969 

 (Hida, 1970a) and cruise 117 to the Samoa Is- 

 lands in February-April 1970 (Hida, 1970b). 

 In this study, Stolephonis hiiccaneeri was first 

 found in the stomach contents of bigeye and skip- 

 jack tunas caught in the equatorial eastern Pa- 

 cific and again in the stomach contents of tunas 

 caught around the Samoa Islands. Since there 

 has been no food study made of tunas and dol- 

 phins from these areas and very few reports 

 on the distribution and biology of S. huccaneeri, 

 it is the intent of this paper to (1) describe 

 the food items of the tunas and dolphins caught 

 in these two geographically distant and environ- 

 mentally diverse — oceanic versus insular — areas, 

 (2) extend the known distributional range of 

 S. hiLccaneeri, (3) report on biological informa- 

 tion obtained from the anchovy specimens. 

 Charles H. Gilbert is a U.S. Department of Com- 

 merce, NOAA research vessel assigned to the 

 Southwest Fisheries Center, Honolulu Labora- 



^ Southwest Fisheries Center, National Marine Fish- 

 eries Service, NOAA, Honolulu, HI 96812. 



tory. National Marine Fisheries Service. Ob- 

 jectives of the cruises were to assess the distri- 

 bution and abundance of surface swimming- 

 tunas, to tag and release skipjack tuna {Katsu- 

 ivonus pelamis) and yellowfin tuna (Thiinnus 

 albacares) for migration and growth studies, 

 and to collect olood samples of these tunas for 

 subpopulation studies. Tunas and dolphins were 

 caught by live bait pole-and-line fishing and by 

 trolling. Threadfin shad, Dorosoma petenense, 

 were transported from Honolulu in baitwells on 

 both cruises and used as chum for the fishing 

 operation. It was the exclusive baitfish used on 

 cruise 116, while on cruise 117 supplementary 

 baitfishes, mostly sardines, Sardinella melaniira 

 and Herklotsichthys punctatus, and a mackerel, 

 Rastrelliger kanagurta, were caught in Pago 

 Pago Harbor and used. Since anchovies were 

 not used as live bait on either cruise, the occur- 

 rence of 5. buccmieeri in the stomachs of the 

 tunas examined indicates that this species is a 

 natural food item in this area. 



Many studies have been made on the food and 

 feeding habits of tunas in the Pacific. Ronquillo 

 (1953) examined the stomach contents of yel- 

 lowfin tuna, skipjack tuna, kawakawa {Euthyn- 

 nus af finis), and the common dolphin {Cory- 

 phaena hipjnirus) caught in Philippine seas. 



Manuscript accepted July 1972. 



FISHERY BULLETIN: VOL. 71, NO. I, 1973. 



135 



