MATERIALS AND SAMPLING METHODS 
For this study ovaries taken from fish captured on longline gear were preserved in 
approximately 10-percent formalin. Material from the Hawaiian area was obtained at the auction 
room of the Kyodo Fishing Company, Ltd., where most of the catch of the Honolulu longline 
fleet was sold. Here the ovaries were taken from fish that had been kept on ice for as long as 
3 weeks after capture. Over a period of 2 years, beginning in November 1949, ovaries of 503 
bigeye were collected. POFI observers with Japanese tuna mothership expeditions that operated 
among the Marshall and Caroline islands in the area bounded by 1 and 10 N, latitude, 145 and 
179°R. longitude during the period of April to October 1951 collected ovaries from bigeye cap- 
tured there. Collections from the central equatorial Pacific were made on POFI exploratory 
fishing expeditions, which covered an area bordered by the latitudes of Ng N. and 10 S. and the 
longitudes of 170 W. and 119 ow, These cruises covered a period of 2 years from August 1951 
to August 1953 and produced collections of ovaries for all months except April and December, 
Data recorded at the time of collection included the weight or fork length of the fish, or 
both, and the date and location of capture. The ovaries were weighed at the laboratory after 
excess tissues such as the mesovarium and the attached blood vessels had been removed, The 
data are presented in the appendix, 
Because the ovaries were obtained from longline catches as opportunity arose, the col- 
lections were deficient in several respects. The coverage of time and space was sparse, and 
bigeye below 30 kg. (66 lbs.) were not well represented in the longline catches. 
DESCRIPTION OF OVARIES 
The ovaries are paired elongate organs, circular in cross-section, lying along the dorsal 
wall of the body cavity, They are separate from each other except posteriorly, where the ovi- 
ducts join just before entering the cloaca, In immature fish (13 kg., or 29 lbs., was the weight 
of the smallest examined) the ovaries are small (about 1 cm. in diameter) and firm, As the 
fish approach spawning condition, their ovaries become enlarged both in length and in girth, 
A large ripe fish may have ovaries as much as 10 cm, in diameter. The ovaries are rather 
flaccid when spent, 
Longitudinal projections of the ovary wall incompletely partition the lumen and serve as 
supports for the follicular tissue, Cross-sections of immature ovaries show a plumate arrange- 
ment of the follicular tissue with the partitions as 'rachises'', This arrangement is obscured by 
large ova in maturing and mature ovaries. 
DESCRIPTION OF EGGS 
As in other fishes, the ovary of the bigeye contains a large reserve of small, transparent 
"primitive'' or undeveloped eggs which periodically give rise to smaller numbers of developing 
eggs. The number of undeveloped eggs ina pair of ovaries, as estimated from a frequency dis- 
tribution of diameters civee eggs in the ovary (fig. 1), is approximately 1 billion. The primitive 
eggs average 0.07 mm.—’ and may be as large as 0.18 mm, in diameter. As these eggs develop, 
the deposition of yolk granules enlarges them and makes them opaque. They are fully opaque at 
a diameter of 0,20 mm, at which stage the weight of the ovary is about 0.004 of the weight of the 
fish (see page 10). Continuing deposition of yolk granules causes further enlargement of the egg, 
and when a diameter of 0.75 mm, is reached, oil globules begin to appear. 
The beginning of translucence in larger eggs signifies the approach of ripeness, The 
mature eggs are translucent and spherical, Diameter frequencies of this group show modes at 
0.88 mm, to 1.1mm, Each ovum contains, ina sac, an oil globule, which appears as a yellow 
spot measuring 0.240 to 0.274 mm, in diameter. The oil is sometimes divided into smaller, 
brighter yellow spots due to the rupture of the sac. When this happens, the empty sac is usually 
seen with ease under magnification, 
Based on formalin-preserved material. 
