154 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



a gross examination of the ovaries would suffice. 

 This consisted of recording the stage of develop- 

 ment of the ovary by noting the general ap- 

 pearance and characteristics of the largest ova 

 present. Additionally, 25 of the largest ova were 

 measured to give an indication of the maximum 

 sizes comprised in each ovary sample. For early 

 developing ovaries, with ova in the primitive and 

 early developing stages, no measurements were 

 made; only the stage of development was noted. 



DEVELOPMENTAL STAGES 



Ovaries were classified as "early developing", 

 "late developing", or "advanced", according to 

 the stage of development of the largest ova 

 present. The characteristics of ova in these 

 stages have been described by Otsu and Uchida 

 (1959b). Briefly they are: 



Early developing. — In this stage the ovaries 

 contain only the transparent primitive ova, or ova 

 that are in the beginning stages of development 

 and are semi-opaque from deposition of yolk 

 granules. 



Late developing. — This is a broad category in 

 which the ova are completely opaque from the 

 heavy accumulation of yolk granules; their dia- 

 meters range from about 0.4 to 0.8 mm. 



Advanced. — In this stage the ovaries are ap- 

 proaching ripeness. The largest ova are semi- 

 transparent and contain a conspicuous golden- 

 yellow oil globule. These advanced ova, not 

 fully ripe, range from about 0.7 to 1.0 mm. in 

 diameter. 



RESULTS 



Seasonal variation in gonad development 



Table 2 shows the number of ovaries of each 

 developmental stage found each month. The 

 six ovaries classified as advanced (2 each in Sept. 

 and Oct. 1957 and Jan. 1958) contained ova in the 

 transitional stage between late developing and 

 advanced, just beginning to take on the charac- 

 teristic semitransparent appearance. The ova 

 diameters (0.60 to 0.64 mm.) resembled more 

 closely the late developing than the advanced 

 stages of Hawaiian albacore ovaries (Otsu and 

 Uchida, 1959b). In comparison, the most highly 

 developed albacore sampled in Hawaiian waters 

 possessed ova with a modal diameter of 0.85 mm. 



The percentage of ovaries in the late developing 

 and advanced stages is shown for each month 



Figure 4. — Percentage of ovaries in the late developing 

 and advanced stages, by month. 



beginning with July 1957 (fig. 4). There is a 

 gradual increase in development, with the peak 

 appearing in December. In May, practically all 

 of the ovaries are in the early developing stage. 

 The increasing trend appears again after May. 

 The 100-percent occurrence of the late developing 



Table 2. — Developmental stages of ovaries shown by month 

 of capture 



Date 



July 



August 



September- 

 October 



November- 

 December.- 



January.. 

 February. - 



March 



April 



May .- 



June 



July 



August 



September. 



Total. 



I9S8 



Number in each stage 



Early 

 developing 



Late 

 developing 



Advanced 



Total 



7 

 51 

 42 

 24 

 22 

 62 



60 

 65 

 65 

 74 

 47 

 89 

 101 

 76 

 7 



782 



