MATURITY AND SPAWNING OF ALBACORE 



295 



definitive measure of maturity, since regardless of 

 their size, the testes of albacore in Hawaii invari- 

 ably contain some milt. It was decided, there- 

 fore, that only the ovaries would be used for the 

 study of sexual maturity of the Hawaiian and 

 central equatorial Pacific albacore. 



Examination of the ovaries from 56 fish revealed 

 varying degrees of maturity from early developing 

 to advanced. Eleven fish ranging in weight from 

 36 to 59 pounds possessed early developing 

 ovaries; 42 fish, ranging from 33 to 62 pounds, had 

 late developing ovaries; and 3 fish, of 41 , 47, and 

 60 pounds, contained advanced ovaries. The 

 frequency distributions of egg diameters for the 

 42 late developing and 3 advanced ovaries, and 

 for 4 of the early developing ovaries are presented 

 in table 7. No measurements were made on the 

 remainder of the early developing ovaries with the 

 exception of noting their maximum egg diameters; 

 none exceeded 0.23 mm. The data (table 7) are 

 arranged progressively from the early developing 

 to the most advanced ovaries as determined by 

 the position of the last mode. The modal diam- 

 eters indicated here were selected by eye after the 

 data had been smoothed twice by a moving 

 average of three. Most of the ovaries showed 

 a distinct second mode which is also indicated. 



The modal diameters of the most advanced 



eggs in each of the 56 ovaries of Hawaiian fish 

 are shown in figure 8 by date of landing. The 

 modal diameters of the 11 early developing ova- 

 ries are plotted arbitrarily at 0.167 mm. (10 

 micrometer units) although the true mode was 

 considerably below this value; only eggs larger 

 than 10 micrometer units were measured. 



Of the 36 ovaries sampled in May, June, and 

 July, 3 were advanced and 33 were in the late 

 developing stage; none was in the early develop- 

 ing stage. In August and September, however, 

 of 14 examined, only 7 were in the late develop- 

 ing stage; the remainder were early developing. 

 In October and November, of 6 examined, only 

 2 were in the late developing stage and 4 were 

 early developing. The above may be an indica- 

 tion that some spawning took place during the 

 summer months. Although the 3 advanced ova- 

 ries were not fully ripe, the appearance of the 

 eggs suggested that spawning was not far distant. 

 Clark (1929) examined 21 albacore from Hawaiian 

 waters during the summer of 1929 and reported 

 that all of these fish were "practically mature 

 and ready to spawn." On the other hand, it is 

 possible that albacore have a protracted spawning 

 season, and that the apparent summer spawning 

 season in Hawaii merely reflects seasonality in 

 their occurrence in these waters (table 1). 



MAY 



JUN 



SEP 



OCT 



NOV 



Figure 8. — Modal diameter of the most advanced group of eggs shown by date of landing for each of the 56 albacore 



from Hawaiian waters. 



