Acanthurus triostegus sandvicensis — RANDALL 
261 
Fig. 24. Length frequency distribution of Acanthurus triostegus sandvicensis. Based on 426 specimens 
caught in traps from Kewalo Basin to Koko Head, Oahu, from Apr. 2 to 9, 1954. 
other with its caudal spine and the latter ulti- 
mately died. The remaining fish died in 1955 
because of an accident. 
BEHAVIOR 
Migration 
Small juvenile manini tend to remain in the 
tide pool or shallow water area to which they 
first come from the pelagic state. Some evidence 
for this has already been presented. Of 176 ju- 
veniles taken in the weekly collections during 
a season from the tide pool of Figure 4, only 
19 were 30 mm. or more in standard length and 
hence definite migrants to the pool from other 
areas. Since all of the fish in this pool were 
killed with rotenone each week, a much greater 
movement to such a large unoccupied area would 
be expected from the smaller adjacent pools if 
the species did not exhibit a tendency to remain 
in one location. When the adjacent pools were 
sampled for manini, they invariably contained 
many more specimens 30 mm. or larger, than 
less than 30 mm. It should be emphasized that 
these pools are isolated from one another for 
only about an hour or less during the infrequent 
low tides less than 0.0 ft. Even in areas like the 
shore of the Ala Wai Canal and the Ala Wai 
Yacht Basin where adjacent areas are freely 
available at all times and essentially identical in 
cover and food supply, appreciable movement 
does not take place. This is attested by the suc- 
cess in recovery of marked fish at the mouth of 
the Ala Wai Canal (Fig. 19, Table 8). Failure 
to take more of these fish was not due to their 
movement out of the area but to the difficulty 
in catching them. Less than one-fourth of the 
manini sighted were caught, and probably many 
others were hidden from view under large rocks, 
etc. None of the fish were taken farther than 
20 ft. from the point of release, although the 
shore was searched as much as 100 ft. away. 
On March 7, 1953, a juvenile manini, esti- 
mated 36 mm. in standard length, was seen next 
to the sea wall of the Ala Wai Yacht Basin be- 
side a pier. It was probably among the first 
manini of the season to come into the area, and 
was the only individual this size visible for over 
100 ft. of sea wall on either side of the pier. On 
the 9 different days up to March 28 when at- 
tempts were made to find this fish, it was seen. 
Its greatest movement from the place where first 
observed was only 12 ft. On March 28 it was 
caught (measured as 41 mm.), and the posterior 
part of the soft portion of the dorsal fin removed 
in order to identify it with greater certainty in 
further observations. It was found on 10 dif- 
ferent days up to May 2, but never more than 
12 ft. to either side of the pier. On April 24 
the dorsal fin had almost completely regenerated 
and by May 2 the fin appeared normal. 
As juvenile manini grow, they migrate sea- 
ward from the tide-pool zone (in the harbor 
area, as mentioned, the larger fish remain in 
shallow water because of the lack of cover and 
