not probable that intermittent egg or larval 

 losses would result in dominant peaks such as 

 are seen in the size-frequency distributions, 

 especially since they appear at the same size 

 each year. Alternately, a very restricted and 

 rigid size selection by longline gear could be 

 occurring in the midwater environment fished by 

 longlines causing the appearance of sharp peaks 

 in the size frequencies; in this case age groups 

 would not be evident in longline samples. Until 

 the migratory habits are clearly under stood and 

 we are better able to sample segments of the 

 whole population it is doubtful that size-frequency 

 studies will produce a description of growth. 



SUMMARY 



1. Male yellowfin in Hawaii att£iin greater size 

 than females. The sex ratio in the Hawaiian 

 fishery is about 1:0.6 in favor of the males, 

 and this ratio is fairly stable throughout the 

 year. 



2. In the Hawaiian fishery there are no great 

 year-to-year differences in the yellowfin 

 size distribution. 



3. Smellier yellowfin (100-130 pounds) enter 

 the fishery in June and July and the larger 

 fish {>130 pounds) in August and September. 



4. Yellowfin size measurements for 1948-1953, 

 while agreeing in general with the growth 

 rate described by Moore (1951), suggest that 

 the no-growth period he reported (June to 

 October) is not real, though there seems to 

 be a slackening of the growth rate in the 

 latter half of each year. 



5. The equatorial yellowfin exhibit the same size- 

 connposition characteristics as the Hawaiian 

 specimens, namely size differences between 

 sexes, and only minor differences between 

 years. 



6. In the equatorial region there is no modal 

 progression with time. 



7. Examination of size-frequency distributions 

 from the western equatorial Pacific, central 

 equatorial Pacific, and Hawaiian Islands in- 

 dicates that when nnodes do occur they are 

 all in similar positions, and that certain 

 modal groups are frequently or consistently 

 missing from distributions in the central and 

 western equatorial samples. 



LITERATURE CITED 



BROCK, VERNON E. 



1943. Contribution to the biology of the 

 albacore ( Germo alalunga ) of the 

 Oregon Coast and other parts of the 

 North Pacific. Stanford Ichth. Bull. 

 2(6): 199-248. 



1954. Some aspects of the biology of the 

 Aku, Katsuwonus pelamis, in the 

 Hawaiian Islands. Pacific Science 

 8(1):94-104. 



EGO, KENJI, and TAMIO OTSU 



1952. Japanese tuna-mother ship expedi- 

 tions in the western Equatorial Pa- 

 cific Ocean (June 1950 to June 1951). 

 U. S. Fish and Wildlife Service, 

 Com. Fish. Rev. 14(6):1-19 (also 

 available as separate No. 315). 



JUNE, FRED C. 



1950. Prelinninary fisheries survey of the 

 Hawaiian-Line Islands area. Part 

 I--The Hawaiian longline fishery. 

 U. S. Fish and Wildlife Service, 

 Com. Fish. Rev. 12(l):l-23 (also 

 available as separate No. 244). 



1953. Spawning of yellowfin tuna in Hawai- 

 ian waters. U. S. Fish and Wildlife 

 Service, Fishery Bull. 54(77):47-64. 



KISHINOUYE, KAMAKICm 



1923. Contributions to the comparative 

 study of the so-called scombroid 

 fishes. Jour. College of Agric., 

 Imperial Univ., Tokyo, 8(3):293-475. 



MARR, JOHN C, and MILNER B. SCHAEFER 

 1949. Definitions of body dinnensions used 

 in describing tunas. U. S. Fish and 

 Wildlife Service, Fishery Bull. 51 

 (47):241-244. 



MOORE, HARVEY L. 



1951. Estimation of age and growth of 

 yellowfin tuna ( Neothunnus macrop - 

 terus) in Hawaiian waters by size 

 frequencies. U. S. Fish and Wild- 

 life Service, Fishery Bull, 52(65): 

 133-149. 



MURPHY, GARTH I., and KEITH C, ELLIOTT 



1954. Variability of longline catches of 

 yellowfin tuna, U, S. Fish and Wild- 

 life Service, Spec, Sci, Rept, : 

 Fisheries No, 119:1-30, 



12 



