218 
PACIFIC SCIENCE, Vol. XV, April 1961 
Another low chlorinity (3.62 %©) was ob- 
tained in a sample taken from the shore of the 
Ala Wai Canal at the Ala Moana Bridge on 
February 23, 1954, following a heavy rain. Al- 
though manini could not be seen at the time 
because of the turbidity of the water, they were 
observed in the area prior to the rain and after 
the water had cleared. 
The highest chlorinity was 21.30 %c. The 
water sample was taken from the pool at Ma- 
kapuu Point in which the 35.1° C. temperature 
was recorded. 
Experiments on Temperature Tolerance 
The experiments on temperature tolerance 
were performed on manini which were main- 
tained in aquaria at a near-constant temperature 
of 24° C. for at least 24 hr. The fish were placed 
singly in a gallon jar of sea water at the tempera- 
ture of the aquarium from which they were 
taken. The jar was then lowered into a water- 
filled copper compartment containing either a 
heating unit or a refrigerating unit and brought 
to the test temperature in 1 hr. ± 10 min. The 
fish were kept at this temperature for 1 hr. If 
death ensued before the end of this hour, the 
time was recorded. The duration of the test 
period was chosen as a rough approximation of 
the temporal conditions of exposure to tempera- 
ture extremes experienced by manini in high 
tide pools. Throughout the tests the jar was 
strongly aerated. 
At about 5° C. before the maximum or mini- 
mum temperatures were reached, the fish began 
to increase their rate of swimming and darted 
around the jar. As the lethal temperature was 
approached more closely, the equilibrium of the 
fish was affected. They swam on one side, upside 
down, or in small circles. The last major activ- 
ity was usually a rapid, spasmodic, swimming 
movement, often in a short spiral. 
The results, except those of tests of both ju- 
veniles and adults run at temperatures of 36.5° 
C. or less and 13° C. or greater (which caused 
no deaths) , are shown in Table 1. 
Although the data are not adequate to deter- 
mine individual variation in the region of the 
temperature extremes, it seems evident that a 
range of about 13° to 36° C. is withstood by 
TABLE 1 
Temperature Tolerance of 
Acanthurus triostegus sandvicensis 
STANDARD 
LENGTH 
(mm.) 
1 TEST TEMP. 
(° c.) 
MINUTES 
TEST TEMP. 
ENDURED 
96 
37.0 
45 
97 
37.0 
60 
137 ' 
37.5 
25 
96 
37.6 
10 
86 
38.0 
4 
97 
38.0 
15 
101 
38.2 
6 
103 
38.3 
20 
26 
36.8 
40 
27 
37.2 
60 
28 
37.5 
60 
34 
37.6 
15 
29 
37.8 
60 
28 
38.0 
60 
29 
38.0 
18 
28 
38.1 
2 
103 
13.3 
60 
95 
12.2 
60 
140 
10.1 
10 
122 
9.0 
2 
25 
13.6 
2 
27 
12.8 
10 
27 
12.5 
60 
28 
11.6 
5 
27 
11.0 
60 
32 
10.8 
8 
this species in the Hawaiian Islands, disregard- 
ing the possible extension of this range by ac- 
climatization. 
Although the range of temperature which ma- 
nini can withstand appears to be extralimital to 
the extremes normally encountered by the spe- 
cies in the Hawaiian Islands, information sup- 
plied by D. W. Strasburg in a letter suggests 
that juvenile manini in the southern Marshall 
Islands are, upon occasions, killed in tide pools 
by heat. On August 17, 1950, a high tide pool, 
about 30 sq. ft. in surface area and 1 ft. deep, 
on the ocean side of Arno Atoll was observed 
at low tide to contain two small Acanthurus 
triostegus triostegus and one small Istihlennius 
edentulus. Several hours later the two manini j 
were dead. The blenny was still living. The 
temperature of the pool at mid-depth was 41° C. 
