254 
PACIFIC SCIENCE, Vol. XV, April 1961 
50 
$ 96 fish, 27.5 to 28 mm, Diamond Head tidepool, May 10, 1953. 
0 10 fish, 28.5 to 30 mm, Ala Wai Yacht Basin, April 24, 1953. 
*£ 45 
E 
JZ 
40 
35 
30 
Apr. 20 Apr. 30 May 10 May 20 May 30 June 9 June 19 
Time 
June 29 
Fig. 19- Growth of juvenile Acanthurus triostegus sandvicensis on Oahu. Based on recovery of marked 
fish. 
considered as the probable rate of growth in 
spring of early juveniles of the bulk of the 
Oahu manini population. 
The growth of juveniles in the winter ceased. 
This was first noticed from shallow-water col- 
lections and observations made during the fall 
and winter months of 1952-53. Up to Novem- 
ber, manini less than 40 mm. could usually be 
found in the collections or seen in the water. 
In late November, December, and January no 
specimens less than 40 mm. were found, but the 
40 mm. size persisted. This suggests that the 
last incoming juveniles of the season, which en- 
ter tide pools in early October, grow to a stand- 
ard length of about 40 mm. by November and 
then stop growing. During the next two winters 
the same phenomenon was noted. 
In order to demonstrate this cessation of 
growth and to ascertain the time when growth 
is resumed, 22 juvenile manini, 40 to 72 mm. 
long, were caught with a dip net, marked by 
fin clipping, and released on the nights of Jan- 
uary 5 and 6, 1954, at the entrance of the Ala 
Wai Canal to the Ala Wai Yacht Basin, Oahu. 
Fish were taken at both the northwest (Wai- 
kiki Yacht Club) and southeast shores of the 
canal entrance. On the two sides of the canal 
three basic methods of fin clipping were uti- 
lized: the top of the caudal fin was removed, 
the bottom of the fin, and both the top and 
bottom. Manini of variable size were chosen for 
each category, and another fin was cut on each 
specimen. Also any distinctive color marks ( usu- 
ally at the base of the pectoral fin) were noted. 
Subsequent efforts to recover the fish were 
limited by conditions of wind, tide, and tur- 
bidity of the water. Although more subject to 
the effects of turbidity than exposed shores, the 
Ala Wai area was preferred, for fish are more 
restricted to the shore area because of the mud 
bottom away from the bank of the canal. Fish 
of this size in a region such as Diamond Head 
move well out on the reef where the broader 
area, deeper water, and action of surf make them 
difficult to capture and recapture. Although, as 
mentioned, some of the larger manini come into 
tide pools at night, their numbers are not suf- 
ficient for such a marking program. 
Since fish were measured alive with a light 
at night, difficulty was experienced in obtaining 
