Biology of the Aku — Brock 
101 
begin early enough in subsequent years to 
span the entire spawning season, with the 
possible exception of 1950; hence, the ana- 
lysis of the data for those seasons will be 
presented. However, the study of the data 
for the 1948 season gave equivalent results 
for the short period covered. 
Given in Figure 3 are the mean of the ova 
diameters measured, averaged for each month 
for 1949 , 1950 , and 1951. Large ova first ap- 
pear in late February, March, or April and 
are found until September. During the re- 
mainder of the year the ova are small. Pre- 
sumably, eggs are maturing between March 
and September but not during the other 
months of the year. Not until after the pre- 
sumed end of the spawning season in Sep- 
tember are fish with flabby, empty ovaries 
encountered. During the summer when the 
ovaries attain their greatest growth, spawned- 
out fish are evidently not available to the 
fishery. The spawning season, as indicated by 
Figure 3, is a long one, and aside from its 
length there are a number of other character- 
istics which may guide some guesses regard- 
ing its important features. These are: (1) The 
great rarity of fish containing fully matured 
eggs in the commercial fishery; (2) the lack 
of fish with ovaries sampled within the spawn- 
ing season which present the spawned-out 
appearance to be observed in those fish ova- 
ries sampled after mid-September; (3) the 
apparent absence of a trend in mean ova 
diameters during the spawning season which 
is shown in Figure 3; and (4) the multimodal 
frequency distribution of ova diameters dur- 
ing the spawning season, as shown in Figure 
4, in which the diameters of 1,000 ova meas- 
ured from a single ovary are plotted. At other 
times, aside from a few large eggs being re- 
sorbed immediately following the spawning 
season, only a single modal diameter of ova 
is in evidence, and this is quite small-— less 
than 0.1 millimeter. 
Assembling these observations into a pat- 
tern is not difficult; however, there are ad- 
mittedly other patterns possible. The multi- 
Fig. 4. Size frequency of ova taken from a single 
ovary, summer of 1949. 
modal distribution of ova diameters during 
the spawning season and its absence at other 
times would infer that individual fish spawn 
several times. This inference is strengthened 
by the absence of an over-all trend in ova 
diameters during the spawning season (that 
is, the dominate diameters do not progress- 
ively increase or decrease) and perhaps also 
by the absence of fish that are obviously 
spawned-out until after the end of the spawn- 
ing season. 
Table 2 gives the relative proportion in the 
samples of ova diameters of certain sizes. 
Although fish with ova approaching 0.7 or 
0.8 millimeter in diameter were quite rare, 
fully mature ova are over 1 millimeter in dia- 
meter. This may imply that fish with ova 
diameters of 0.7 millimeter and above become 
