Olfaction and Sharks — -Tester 
147 
the blinded sharks to olfactory substances was 
considerably less variable than that of sharks 
with normal vision. 
Except during starvation experiments, the 
sharks were fed sparingly about once or twice a 
week; uneaten food was removed to avoid putre- 
faction and an unnecessary increase in olfactory 
level. 
After investigating several different tech- 
niques during the early summer of 1959, a stan- 
dard method of testing materials which could 
be dissolved or suspended in water was adopted. 
With natural foods such as fish flesh, usually 5 
gm of material was macerated in a Waring 
blendor for 5 min with 250 ml of fresh water; 
sea water was not used because essential oils 
tended to accumulate in the froth. The material 
was then filtered and held in a refrigerator until 
used. Prior to an experiment a small quantity 
(usually 3.0 ml) of the clear solution was di- 
luted with sea water to 25 ml in a test tube and 
then further diluted to 100 ml with sea water in 
a funnel. Substances other than natural foods 
were diluted to various concentrations before 
being tested. 
Prior to testing, a glass funnel and tube lead- 
ing from the observation booth to a point just 
below the surface in the center of a test area 
(e.g., Fig. 2, Tank 1, D) was filled with sea 
water to remove air bubbles; the contents were 
maintained by closing a pinchcock. The flow of 
sea water to the tanks was shut off at the inflow 
valve. Usually, five 2 -min control periods were 
then run, during each of which the time (sec- 
onds) spent by one or more of the sharks in 
the test areas (e.g., Tank 1, C and D) was re- 
corded by an electric timer activated by a foot 
switch. At the same time, observations were re- 
corded of the behavior of the sharks and some- 
times of the number of passes or turns in the 
test areas. The test material was then introduced 
silently while the sharks were at the far end of 
the compartment, and the activity of the sharks 
was again noted and recorded during five (or 
more) 2 -min test periods. The nature of the 
response was then categorized as attraction, re- 
pulsion, etc. on the basis of the graphed data 
and the notes. 
A similar technique was used in I960 except 
that timing was abandoned in favor of counting 
the number of turns. Each of the two test areas 
was divided by an imaginary line into halves; 
turns in the four half-areas were given weights 
of 1 to 4, with the weights increasing toward 
the half-area of introduction (Fig. 2). The 
graphed "count index” of activity seemed to re- 
flect our subjective impression of a response 
SEAWATER 
Fig. 2. Diagram of shark tanks at Eniwetok Marine 
Biological Laboratory. 
