MATURITY AND SPAWNING OF ALBACORE 



301 



method for making rapid field determinations is 

 desirable. The size of the ovaries, if directly 

 related to maturity, should provide a reasonable 

 criterion. Our data show that all of the early 

 developing ovaries from the central equatorial 

 Pacific weighed less than 100 grams, and that 

 late developing ovaries ranged from 104 to 363 

 grams. The early developing ovaries from the 

 Hawaiian area, however, ranged in weight from 

 54 to 179 grams, the late developing ovaries from 

 123 to 805 grams, and the three advanced ovaries 

 weighed 181, 538, and 916 grams, respectively. 

 Thus, while the ovaries from the central equatorial 

 Pacific fall conveniently into two stages of 

 maturity according to their weights, there m 

 considerable overlap in the Hawaiian samples. 

 It appears, therefore, that ovary size is actually a 

 poor criterion to follow in assessing the state of 

 maturity of an ovary. 



Recently, the relative ovary weight (ovary 

 w r eight X 10 3 /fish weight) has been found to be 

 a fairly reliable measure of maturity for Hawaiian 

 yellowfin (June 1953) and central Pacific bigeye 

 tuna (Yuen 1955). This relation was therefore 

 tested for the albacore ovaries. In figure 1 2 the rel- 

 ative ovary weight of each of the Hawaiian and 



central equatorial Pacific albacore is plotted against 

 the maximum egg diameter. Here again, the 

 data do not permit the use of modal diameters, 

 for these were not determined for most of the 

 early developing ovaries. The data presented in 

 tables 7 and 8 indicate an acceptable correlation 

 between modal and maximum diameters which 

 justifies the use of the latter. The early develop- 

 ing ovaries, with only one exception, have rela- 

 tive ovary weights of less than 6, while all but 

 three of the late developing ovaries have relative 

 ovary weights greater than 6. Thus, with a 

 reasonable amount of confidence, a relative ovary 

 weight of 6 may be considered as the value which 

 separates the earlydeveloping from late developing 

 ovaries. 



The late developing ovaries ranged in relative 

 ovary weight from 6 to 30 with a general ten- 

 dency for the ratio to increase with progressing 

 maturity. The three advanced ovaries, however, 

 failed to conform to any pattern and varied in 

 relative ovary weights from 10 to 34. Despite 

 the large variation exhibited by the three ovaries 

 in the advanced stage, the data in general point 

 to a definite relation between relative ovary weight 

 and the state of gonad development. 



12 14 16 18 20 



RELATIVE OVARY WEIGHT X I0 3 



Figure 12. — Relation between relative ovary weight and state of maturity. 



