292 



Fishery Bulletin 100(2) 



700 



600 



500 



E 



- 400 



300 



200- 



100 



A Cephalopod prey 

 D Crustacean prey 

 • Fish prey 





400 



600 800 1000 1200 1400 



Dolphinfish fork length (mm) 



1600 



1800 



07 



ra 06 



c 



(D 



03 



05 



04 



CL 



1, 03 



c 

 a 



g- 02 

 0.1  



B 



fi Cephalopod prey 

 n Crustacean prey 

 • Fish prey 



• .. • • • . • 



•^ f •^•T ** — i"  — V r- 



400 



600 



800 



1000 



1200 



1400 



1600 



1800 



Dolphinfish fork length (mm) 



Figure 6 



The length or maximum dimension of the prey (A) and pi-ey relative sizes (Bi versus 

 dolphinfish size for three prey groups found in the stomach contents of common dol- 

 phinfish in the eastern Pacific Ocean. The lines represent the data smoothed with a 

 smoothing spline, excluding the point for the largest dolphinfish. 



In the southwest area, few large common dolphinfish 

 were sampled (Table 1). The flyingfishes were important 

 prey for the four smallest size groups (up to 1100 mm). 

 Epipelagic cephalopods were important for the smallest 

 and two largest size groups. Auxis spp. represented over 

 46% of the diet of dolphinfish between 651 and 800 mm 

 fork length (Fig. 5, southwest). 



In the southeast area, the epi pelagic cephalopods domi- 

 nated the diet (52-90% ) of dolphinfish of all five size strata 

 (Fig. 5, southeast). The flyingfishes comprised most of the 

 remaining prey composition in the 651-800 and 801-950 

 mm categories, and Thuruiiis spp. (assumed to be mostly 

 yellowfin tuna) comprised most of the remaining in the 

 951-1100 and 1101-1250 mm categories. 



Prey size 



We present the sizes of cephalopod, crustacean, and fish 

 prey found in the dolphinfish stomach contents in Figure 

 6A. Intact prey ranged from 14 to 650 mm in length, 

 and averaged 160 mm overall. The data smoothed with a 

 smoothing spline showed an increasing trend of prey size 

 with dolphinfish size. The maximum prey sizes increased 

 gradually for dolphinfish up to about 760 mm, then 

 abruptly to a maximum of about 600 mm for dolphinfish 

 of approximately 1000 mm. This pattern was largely con- 

 sistent for fish and cephalopod prey. Crustacean prey were 

 small, but were consumed by a wide size range of dolphin- 

 fish. " . 



