234 
ana, Marshall, Gilbert, Line, and Phoenix is- 
lands — groups in which the sea surface tempera- 
ture exceeds 80° F. (26.7° C.) the year-round 
and where the annual variation in sea tempera- 
ture is slight (based on Hydrographic Office, 
225). Examination of these fish revealed ripe 
gonads in every month of the year. Specimens 
of transforming or small juvenile manini col- 
lected every month of the year from these areas 
were found in museums. 
It is, therefore, puzzling that the seasonal 
spawning in the Hawaiian Islands seems to be 
associated with the colder part of the year. The 
mean monthly sea surface temperatures around 
Oahu (1945-55) vary from about 75° to 81° F. 
in an average year (Leipper and Anderson, 
1950; Hydrographic Office, 280.) The tempera- 
ture of the warm part of the year is essentially 
the same as that of the lower latitudes where 
spawning is year-round. The initial enlargement 
of the gonads in Hawaii coincides with the time 
of decreasing sea surface temperature in the fall. 
The marked increase in tide pool recruitment 
in May appears to correspond to increased 
spawning in February-March, the time of cold- 
est water temperature. 
If temperature or some other factor such as 
change in length of day is the cause of inter- 
rupted spawning in Hawaii, then manini in a 
region of the South Pacific Ocean with com- 
parable latitude should spawn seasonally and 6 
months out of phase from Hawaiian manini. 
Unfortunately no data are available from south- 
erly island groups such as the Australs or south- 
ernmost Tuamotus where sea temperatures 
closely approximate those in Hawaii. 
Small juvenile and transforming A. triostegus 
triostegus were taken or observed by the author 
in every month of the year (1956-57) in the 
Society Islands ( where temperatures range from 
about 77.5° to 81° F., or 25.2°-27.2° C). The 
manini is not as abundant in the Society Islands 
as in Hawaii, and the insignificant tide in the 
former island group made it difficult to find 
numerous individuals isolated in tide pools. Col- 
lections were insufficient to demonstrate any 
possible variation in reproductive activity dur- 
ing the year. 
A cyclic fluctuation in the abundance of in- 
coming young within the spawning season in 
PACIFIC SCIENCE, Vol. XV, April 1961 
the Hawaiian Islands is apparent from Figure 
5. The peaks of these fluctuations line up roughly 
with the time of new moon. This correlation is 
more evident from the extensive collections 
made from various tide pools plotted in Figure 
6. The large mode of May 10 centered on a 
standard length of 26 mm. contains 54 trans- 
forming fish. The time of new moon was May 
13. The large mode of April 17 is centered on 
a standard length of 27 mm. and contains 10 
transforming manini. New moon in April oc- 
curred on the 13 th day. 
Tester and Takata (1953: 36, fig. 14) have 
demonstrated a similar lunar periodicity in the 
appearance of young aholehole ( Kuhlia sand - 
vicensis ) in tide pools on Oahu. 
If the periodicity in the influx of manini 
acronuri is a function of some lunar effect on 
the young and not on the spawning adults, then 
the peak fluctuations of incoming acronuri in 
areas of different temperature, and hence dif- 
ferent rates of development (see development 
section), should still correlate with the time of 
new moon. A sample of 108 small manini col- 
lected with rotenone by the author from tide 
pools at Onotoa Atoll, Gilbert Islands, on Au- 
gust 21, 1951 (Fig- 7), demonstrates that this 
is not the case. Onotoa is located in the central 
Pacific (1° 47' S., 175° 32' E,); the monthly 
mean sea surface temperatures vary only slightly 
from 82.5° F. (28.6° C.) throughout the year. 
Full moon occurred on August 16 (new moon 
on August 2) . The large mode of Figure 7 cen- 
tered on about 23 mm. standard length includes 
only 9 transforming specimens which average 
23.5 mm. in standard length. Thus the peak in- 
flux of the fish comprising this mode is esti- 
mated at 4 or 5 days prior to August 21. This 
large Onotoa sample, therefore, is about 1 1 days 
out of phase with the lunar cycle of incoming 
young on Oahu (where the mean monthly sea 
surface temperatures vary from 75° to 76.5° F., 
or 23.9°-24.5° C., from January to April). 
In order to obtain direct evidence of lunar 
spawning by adult manini and to more sharply 
delimit the spawning season, the entire catch of 
two trap fishermen was examined for ripe fish 
on 62 days from June 19, 1953, to September 3, j 
1954. The catch was usually brought to port 
alive. The fishermen would not permit the open- 
I 
