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PACIFIC SCIENCE, Vol. XVII, April 1963 
reasonably certain that most species also attack- 
healthy, undamaged, living prey, although apart 
from attack on man, observations of feeding 
activity are singularly lacking in the literature. 
In the summer of 1959, a group of biologists 
from the Hawaii Marine Laboratory witnessed 
the persistent attack of a tiger shark on a spiny 
puffer which had inflated itself and was floating 
at the surface in Kaneohe Bay. The shark’s at- 
tempts to swallow the puffer (Fig. 8) lasted 
for about 10 min despite the presence of the 
observers who circled in an outboard motor 
boat. During the shark’s slow, awkward passes 
at the puffer the sound of its jaws clamping 
together as it missed the prey could be heard. 
Other species of sharks are capable of catch- 
ing fast moving prey. For example, Eibl-Eibes- 
feldt and Hass (1959) observed both the grey 
shark ( Carcharhinus menisorrah ) and the black- 
tip (C. melanopterus ) actively feeding on 
healthy fish in the Indian Ocean, and even herd- 
ing them against the shoreline to facilitate cap- 
ture. 
Although vision is doubtless the predominat- 
ing sense which is used by sharks on converging 
on living undamaged prey, it is possible that 
olfaction may also be involved. I have found 
only one observation in the literature which 
supports this possibility, that reported by Shel- 
don (1911) and again by Parker and Sheldon 
(1913), who found that the dogshark ( Mustelus 
canis) was able to locate undamaged living 
crabs concealed in a wrapping of eelgrass. The 
response of sharks to living, presumably un- 
damaged fish was investigated at both the Eni- 
wetok and the Hawaii laboratories. 
Results 
In one series of experiments at Eniwetok in 
1959, an empty wire cage (about 6 X 6 X 12 
inches) was silently lowered to the bottom of 
a test area at the upstream end of a compart- 
ment containing four blinded blacktip sharks. 
After the usual series of control periods during 
which activity was recorded, the cage was re- 
moved, a living fish was added, and it was again 
lowered into the test area when the sharks were 
at the far end of the compartment. Activity was 
again observed during a series of test periods. 
The water flow was maintained during both 
control and test conditions. 
The results are included in Table 6. In most 
of the experiments attraction responses were 
obtained with a 12 -inch grouper ( Epinephalus 
fuscoguttatus ) , an 8-inch squirrel fish (Holo- 
centridae), and an 8-inch stone fish ( Synancaja 
verrucosa) . Although probably excited by con- 
finement in the cage, the fish did not move about 
much after the cage had been lowered. There 
was often a delay of several test periods before 
the sharks showed any response. Then, in most 
of the experiments, one or more sharks suddenly 
TABLE 6 
Response of Sharks at Eniwetok Marine Biological Laboratory to Living Fish, 1959 
RESPONSE* 
SHARKS AND FISH 
RR 
R-R? 
O-S 
A-A? 
AA 
Total 
Blinded blacktips 
Caged grouper 
- 
- 
1 
3 
1 
5 
Caged squirrel fish 
- 
- 
1 
1 
2 
4 
Caged stonefish 
- 
- 
- 
2 
- 
2 
Total 
- 
- 
2 
6 
3 
11 
Blinded blacktips 
Grouper water, grouper present 
- 
- 
1 
2 
2 
5 
Grouper water, grouper absent 
- 
- 
2 
- 
1 
3 
Eel water, eel present 
- 
- 
- 
1 
- 
1 
Blacktip water, blacktip absent 
- 
- 
2 
- 
- 
2 
Total 
- 
- 
5 
3 
3 
11 
* RR, strong repulsion; R-R?, weak or doubtful repulsion; O-S, no apparent response or sensing; A-A?, weak or doubtful 
attraction; AA, strong attraction. 
