262 
PACIFIC SCIENCE, Vol. XXI, April 1967 
well extended. When it swam inverted, the 
head was again horizontal and the trunk axis 
dipped about 8° below the horizontal, but the 
caudal fin touched the pool bottom and the pec- 
toral fins were folded. When it swam on its side 
along the wall, the pectorals were half folded 
but the caudal did not touch the wall. The in- 
verted fish kept its head about 1^> inches above 
the bottom, but when swimming on its side 2 
or 3 inches separated the head and the wall. 
In most swimming the caudal fin was well 
expanded to a rhomboidal or oval shape, the 
pelvics were folded, and the dorsal and anal 
fins were only partly erect. The fish’s sinuousity 
was impressive, as it could execute 180° turns 
In a circle about 6 inches in diameter. The pec- 
torals and sometimes the pelvics were erected 
when the fish changed course or its plane of 
swimming, and also when it had just been fed 
to satiation. In addition, the gorged fish occa- 
sionally swam at an angle of 15° to 35° from 
the horizontal. 
Swimming speeds were calculated for each of 
the three swimming attitudes and for the hun- 
gry and fed fish. Data were obtained by timing 
the fish as it swam between reference points on 
the pool’s sides. Speed data are given in Table 
2. In contrast to normal and inverted swimming, 
side-swimming when satiated was observed only 
once. The values given are the extremes of a 
number of readings. The loss of speed after 
feeding was marked but of short duration. Un- 
fortunately, the only data showing this change 
relate to tail-beat frequency, not to speed. Tail 
beats were counted at 66/minute immediately 
after feeding, but suddenly increased to 78 and 
84 beats/minute 11 minutes later. 
TABLE 2 
Swimming Speed for the Lousefish 
RANGE IN 
SWIMMING 
STATE OF FISH 
SWIMMING 
ATTITUDE 
SPEED 
(ft/sec) 
Not fed for 7-12 hr 
normal 
inverted 
on side 
1.61-2.05 
1.88-2.04 
1.41-2.21 
Fed to satiety 
normal 
inverted 
on side 
0.80-1.61 
0.87-1.32 
1.15-1.39 
° MUlNUrltl 
★ SATIATED 
o 
o 
★ 
3 
* 
o 
* 
★ 
* 
°0 25 50 75 100 125 150 175 
NUMBER OF TAILBE ATS/ MINUTE 
Fig. 1. Speed versus tail-beat frequency in the 
lousefish. 
Figure 1 shows the relation between speed 
and tail-beat frequency. Speed and tail-beat data 
were obtained simultaneously as the fish tran- 
sited the pool. The number of beats per minute 
ranged from 48 to 144. No speed estimate was 
obtained for the 48-beat value, which occurred 
2 minutes after gorging and 1 minute before 
the fish sat on the bottom. 
RESPIRATION 
While the lousefish was swimming, its mouth 
was always open and no opercular movements 
were detectable. In this respect it resembled 
Remora remora (Linnaeus), which ceased oper- 
cular pumping under conditions of optimum, 
if artificial, water flow over the gills (Strasburg, 
1957). The speed range (or the flow rate) ob- 
served for the hungry lousefish (1.41-2.21 
ft/sec), however, was more than twice the 
range (0.75-0.88 ft/sec) judged optimal for 
R. remora (Strasburg, 1957). 
When gorged, the lousefish usually sat on the 
bottom or attached. Its mouth remained open 
and opercular respiratory movements were con- 
spicuous. The well-developed tongue was alter- 
nately pressed to the mouth’s roof and returned 
to its bed, in a rhythm keyed to the opercular 
movements. Sometimes the fish oriented to face 
the weak current at the pool’s inlet. The num- 
ber of respirations per minute ranged from 84 
to 120 — a much lower range than for R. remora , 
which had from 203 to 244 respirations per 
