8. The size of the longline-caught yellowfin and bigeye increases from west to east. The 

 differences in size are compatible with apparent differences in the amount of upwelling, 

 suggesting that there are fundannental differences in the growth rates of yellowfin and bigeye 

 annong the western, central, and eastern Pacific, related to the relative productivity of the 

 three areas. 



9. The preponderance of males in longline catches of yellowfin may be a reflection of a higher 

 mortality of females after a certain age. 



10. A method of using the echo sounder to ascertain the depth fished by the longline was devised, 

 and preliminary results of its application are given. In most instances considerable stream- 

 ing of the line prevented it from reaching its maximum possible depth. 



11. In general yellowfin catches were higher on the deep and intermediate hooks, and less on the 

 shallow hooks. Bigeye and albaccre were taken most frequently on the deep hooks. 



12. Experimental fishing indicated that the expensive sekiyama sections of the branch lines can 

 be eliminated. 



13. An estimated 10 percent of the catch was unsuitable for delivery to the cannery because of 

 mutilation by sharks. This figure can probably be reduced in commercial operations. 



LITERATURE CITED 



Austin, Thomas S. 



1954. Mid-Pacific oceanography III, transequatorial waters, August-October 1951. U. S. 



Fish and Wildlife Service, Spec. Sci. Rep. : Fish. No. 131, June 1954, 17 pp., 13figs., 

 stations 29-50. 



Cromwell, Townsend 



1953. Circulation in a meridional plane in the central equatorial Pacific. Jour, of Mar. Res., 

 Vol. 12, No. 2, pp. 196-213. 



Kanagawa Prefecture Fishery Experiment Station 



1952. Monthly Report No. 3, August; No. 4, September; No. 5, October; No. 6, December. 

 King, Joseph E. and J. Demond 



1953. Zooplankton abundance in the central Pacific. U. S. Fish and Wildlife Service, Fish. 

 Bull., Vol. 54, No. 82, pp. 111-144. 



McKernan, Donald L,. 



1953. Pioneer longlining for tuna along the Equator. Pacific Fisherman, Vol. 51, No. 8, 

 July 1953, pp. 19, 21, 23, 



Murphy, Garth I. and T. Otsu 



1954. Analysis of the catches of nine Japanese tuna longline expeditions to the western Pacific 

 Ocean. U. S. Fish and Wildlife Service, Spec. Sci. Rep.: Fish. No. 128, Dec. 1954, 

 46 pp. 



30 



