FOOD OF ALBACORE IN THE PACIFIC 



469 



l*30'N-5*00'N. (3 



l*30'N.-l"50'S, (0) 



l"30'5.-5*OOS. (5) 



kSOO'S. (51 



50 



r30'N.-5'00'H 121 



l"30'M-l'30'a 1 I) 



l'30"S.-5'00'S (41 



>5'00' S. (91 



1.0 



S 6 



I79°W-I79°E. I58°W.-172°W 



I20°W-I45°W, 



LONGITUDE 



Figure 12. — Longitudinal variations in tlie equatorial 

 Pacific of zooplankton and the volume of stomach eon- 

 tents per pound body weight of 121 longline-caught 

 albaeore. ( Numbers in parentheses refer to sample 

 sizes.) Zooplankton data are from King, Austin, and 

 Dot.v (1!).")") and King and Hida (1057) and have been 

 adjusted to remove the effect of diurnal variation ac- 

 cording to the method of King and Hida (1954). 



deeper waters. The highest bigeye stomach con- 

 tent volumes occurred in the western part of the 

 sampling area (155° W.-180°). 



VARIATION IN FOOD WITH SEASON 



Seasonal variation in the food of 78 albaeore 

 troll- or longline-caught in the temperate North 

 Pacific between 140° W. and 180° is shown in 

 table 4. Summer and fall samples were combined, 

 since most of the samples were obtained during 

 the end of smnmer and beginning of fall. There is 

 little dill'erence between the summer- fall and win- 

 ter values, although the range of sampling was 

 10° of latitude broader in summer than in winter. 



Table 4. — Heaxonal variation in food of troll- and longtine- 

 caui/ht albarore from the temperate Xorth Pacific, 

 11,0° W.-ISO" 



Volume In cc./lb. body weight- 

 Number of samples _ __ 



Summer 

 an'l fall 

 (30" N.- 

 49° N.) 



0.8S 

 54 



Winter 



(30° N.- 

 39° N.) 



0.7« 

 24 



Seasonal variation in the food of 143 albaeore 

 lai<eii l)y longlining in the equatorial Pacific is 

 siiown in figure lo. From January throiigli' Sep- 

 tember the amounts of squid and tish pei- stomach 

 do not vary greatly, but from October through 

 December the amount of squid consumed apjji-oxi- 

 mately doubles. This may be due to the smallness 

 of the sample. If we disregard the October 

 through December results as a vagary of sampling, 

 the next higliest values were recorded foi- the 

 April through June period, which agrees fairly 

 well with the results shown by King and Ikehara 

 (1956) for bigeye tuna in the equatorial Pacific, 

 although their sampling period was from April 

 tlirough July. 



VARIATION IN FOOD WITH DISTANCE FROM 

 LAND 



An examination of data on albaeore stomach 

 contents in terms of the distance of the point of 

 capture from the nearest emergent- land was un- 



l-30'N,.5*00'n ( 2 



l'30N.-l*30S. I 3 



r30'a-5-OOS. (141 



>5*00'S. (30 



FiGUBE 13. — Variation in the amount of squid and fish in 

 the stomach contents of 14:{ albaeore captured b.v long- 

 line in the equatorial Pacific, according to season. 

 (Numbers in parcnlhcses refer to sample sizes.) 



