Biology of the Lousefish — Strasburg 
261 
TABLE 1 
Capture Data for Phtheirichthys lineatus 
DATE 
LATITUDE 
LONGITUDE 
SEX* 
STANDARD 
LENGTH 
(mm) 
HOST OR HABIT 
2/ 1/57 
13°44'S 
110°02' W 
p 
55.7 
dip-netted beneath night-light 
10/ 5/62 
19°12'N 
156°05' W 
- 
256 
dip-netted beneath night-light 
10/ 5/62 
19°12'N 
156°05' W 
M 
273 
dip-netted beneath night-light 
9/29/51 
21° 24' N 
158° 15' W 
F 
300 
dip-netted beneath night-light 
10/30/58 
04° 58' S 
149°52' W 
p 
32.8 
caught by British Columbia trawl 
11/ 1/58 
05°00' S 
149°58' W 
p 
48.4 
caught by British Columbia trawl 
8/28/56 
1 1 ° 2 3' S 
134° 32' W 
p 
46.0 
in T hunnus albacares stomach 
7/18/50 
03°00' S 
171 °22' W 
p 
53.0 
attached to longline buoy 
7/20/60 
11°30'N 
161°21'E 
p 
53.2 
attached to longline buoy 
8/26/56 
13°26' S 
132°16' W 
p 
54.0 
attached to longline buoy 
7/18/50 
03°00'S 
171 °22' W 
p 
56.1 
attached to longline buoy 
2/ 7/63 
17°57'N 
149°39' W 
p 
51.3 
attached to longline bait (squid) 
2/23/63 
20°4l'N 
150°06' W 
p 
55.5 
attached to longline bait (squid) 
2/ 7/63 
17°57'N 
149°39' W 
p 
58.9 
attached to longline bait (squid) 
7/31/63 
21°24'N 
149°51' W 
p 
61.6 
attached to longline bait (squid) 
2/ 6/63 
18°16'N 
149°46' W 
p 
92.4 
attached to longline bait (squid) 
8/27/56 
1 2 ° 1 6' S 
133°20' W 
p 
44.0 
attached to longline bait (fish) 
7/24/63 
14°22'N 
149°58' W 
- 
81.3 
attached to longline bait (fish) 
7/10/63 
14°24'N 
150°11' W 
- 
112 
attached to longline bait (fish) 
5/ 5/62 
02°09'N 
157°13' W 
p 
48.9 
attached to dead T hunnus albacares 
2/ 6/63 
18°16'N 
149°46' W 
F 
126 
attached to dead Coryphaena equiselis 
8/29/62 
Kahana Bay, 
Oahu 
p 
59.6 
attached to living Diodon loystrix 
7/18/50 
03°00'S 
171 °22' W 
p 
48.6 
unknown 
3/15/59 
14°49'N 
150°12' W 
p 
60.2 
unknown 
* (?) = sex could not be determined; ( — ) = specimen not dissected. 
of lateral wriggling, or it rested on the bottom 
with its belly down, or it attached to the pool’s 
bottom or side. Each of these activities lasted 
as long as 15-20 minutes and appeared to 
represent a post-gorging rest. Sometimes the 
stuffed fish would regurgitate part of its meal 
and revert to swimming. Although bottom- 
resting was the most common post-feeding act, 
it is unlikely that this could happen in nature 
because substrates suitable for resting would not 
be available. If satiation resulted in such a tem- 
porary weight gain or such a loss of swimming 
mobility that a resting place was necessary, it 
is probable that a wild fish would never venture 
far from its attachment site. It is also probable 
that full meals are rare in the wild. 
The lousefish made no use of its fins when 
resting on the bottom or attached. The large 
caudal was collapsed about its long central 
rays, the dorsal and anal were folded against 
the body, the pelvics were depressed, and the 
pectorals were semiflexed. 
SWIMMING 
Except for the situations noted above, the 
captive lousefish swam constantly in either of 
two patterns. More commonly it swam back 
and forth across the pool, passing near the 
center each time. In a round trip, one passage 
was at the pool’s mid-depth (2 ft) and the 
return just above the bottom (4-ft depth). On 
the mid-depth trip the fish’s attitude was 
normal (disk up) ; on the bottom trip it was 
inverted (disk down). During the short vertical 
connecting trips, the disk faced the tank walls. 
The fish oriented to the walls or bottom when 
6—12 inches from them. Less commonly it cir- 
cuited the pool’s periphery on its side, with 
the disk facing the pool wall. 
Some differences in swimming method were 
noted within these patterns. When the fish was 
swimming with the disk up, the head was es- 
sentially horizontal, the body axis hung about 
8° below the horizontal, and the pectorals were 
