FISHERY BULLETIN: VOL. 71, NO. 4 



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association with tuna in the eastern tropical 

 Pacific. On the basis of knowledge about the 

 depth distributions of the species encountered, 

 they concluded that the spotted porpoise had 

 been feeding within 30 m of the surface and the 

 spinner porpoise had been feeding to 250 m or 

 more beneath the surface. Squid remains were 

 present in some of the stomachs examined by 

 Fitch and Brownell but were not included in 

 their analysis. 



In view of the nonselective feeding habits of 

 the yellowfin tuna, analysis of comparative 

 feeding habits of tuna and porpoise in mixed 

 aggregations must be based on stomach contents 

 collected from two or more of the species taken 

 together in net hauls. 



In this paper we report the results of the 

 examination of stomach contents of 79 tuna, 

 140 spotted porpoise, and 46 spinner porpoise, 

 taken in seine hauls on yellowfin tuna in 1968. 



MATERIALS AND METHODS 



The animals examined were captured in six 

 net hauls by a tuna seiner (Table 1). The tuna 

 were marked with numbered dart-type spa- 

 ghetti tags and placed in the vessel's refrigerated 

 fish holds. Stomachs were subsequently col- 

 lected from the marked fish and preserved en- 

 tire in 10% Formalin'^ when the catch was un- 

 loaded and prepared for processing ashore. 

 Most of the porpoise stomachs were examined 

 in the field and only selected items of the con- 

 tents preserved in 10% Formalin for later iden- 

 tification (Table 1). The remainder of the stom- 

 achs were from animals frozen entire and later 

 dissected ashore. Only the contents of the fore- 

 stomach (oesophageal stomach) were examined. 



The tuna taken during the cruise were nearly 

 all about 1 m long. A random sample of 50 fish 

 ranged from 846 to 1,164 mm fork length (aver- 

 age 1,079 mm). 



The entire contents of stomachs opened in 

 the laboratory were rough-sorted into fish, 

 squid, and crustacean components. Each food 

 item was identified to the lowest possible taxon, 



5 Reference to trade names does not imply endorsement 

 by the National Marine Fisheries Service, NOAA. 



1078 



