Reconnaissance by Submarine — Brock and Chamberlain 
387 
erally sand covered, and rocky areas, either 
outcrops of reef rock or near-vertical rocky 
escarpments separating the terraces. Of the 
latter, the important ones were a line of out- 
crops and low escarpments at 70 meters and 
massive escarpments with crests at 120 meters 
or deeper, paralleling the coast. Associated with 
the rocky areas were an abundance of fishes 
and in places a rich epifauna also. 
The Communities of the Rocky Areas 
Figures 5, 6, and 7, reproducing the actual 
sounding traces of the bottom, also show, more 
faintly and somewhat separated from the 
bottom, traces of what were subsequently dem- 
onstrated to be concentrations of fish. These 
were located generally at or above escarpment 
crests or over outcrops of reef rock. These con- 
centrations of fish were investigated by cruising 
in the "Asherah” near the sea floor, along and 
across the escarpments near where the sound- 
ings were made. In addition, photographic 
transects were made both obliquely to the trend 
of the coast and at a right angle. These ran from 
shallow to deep water in order to minimize 
direct contact of the camera system with the 
bottom. 
The visual observations made from the "As- 
herah” provided a dramatic contrast to the 
photographic ones obtained with the automatic 
camera system. Visual observations confirmed 
the indication given by the echo sounding 
record in finding major, but highly discontin- 
uous, concentrations of fish associated with the 
escarpment crests. This was not true of the 
photographic transects. Fish were photographed 
on only a few frames of the hundreds exposed, 
and those photographed were species that com- 
monly rest on the bottom or swim very near the 
bottom. The greatest number of fish were 
photographed in a few instances when the cam- 
era system was in contact with the bottom, being 
dragged along so that photographs were taken 
parallel with the sea floor. 
Observations from the "Asherah” on the 
relative abundance of some species, suggested 
that the fish community associated with outcrops 
of reef rock at about 70 meters differed from 
that associated with the deeper escarpment 
crests further offshore at depths of 120 meters 
or more. The damsel fish Chromis verater ap- 
peared to be the most abundant species about 
the outcrops of reef rock. The little bass 
Caesioperca thompsoni was common in small 
loose schools on the face of these outcrops. 
Heniochus acuminatus was also common, fre- 
quently as individuals, but sometimes in small 
groups. The surmullet Parupeneus bifasciatus 
was also common near the basal portion of the 
outcrops or around rocks in the vicinity, but 
not in schools. 
The angel fish Holocanthus arcuatus was ob- 
served as scattered individuals over rocky areas, 
usually very close to the bottom. The most 
abundant butterfly fish observed was Chaetodon 
miliaris; however this species was less numerous 
than the damsel fish Chromis verater in the 
rocky outcrop environment. See Figure 8. 
Both Naso hexacanthus and Seriola dumerilli 
were observed in schools at both the outcrops of 
reef rock and the escarpments. The schools of 
Naso appeared to be smaller and more open in 
the shallower water. Naso schools above the crest 
of the deep escarpments, near large aggregations 
of Chaetodon miliaris, had the following char- 
acteristics. The schools were roughly spherical, 
about 3 to 7 meters across, and moved slowly 
between 5 and 15 meters off the bottom. The 
individual fish appeared to be 35 to 70 cm in 
length and swam rather closely together. 
Seriola dumerilli were observed in roving 
schools of a few dozen fish. Individual fish in 
the schools were estimated to be larger than 70 
cm and less than 150 cm in length. 
Mention has been made of aggregations of 
Chaetodon miliaris above the crests of the 
escarpments. These occurred over a relatively 
small area of bottom, usually less than 50 meters 
across, which was somewhat elevated (by 5 
meters or less) above the general height of the 
escarpment crest. The aggregation, or school, 
extended upward into the water column from 
15 to 40 meters. Individual fish were 12 to 25 
cm in length and appeared to be separated by 
distances of 0.5 to 2 meters or more apart. The 
fish were close to the bottom but confined to the 
rocky elevated portions. They did not occur 
down over the face of the escarpments and the 
diameter of the aggregation appeared to be less 
with increased distance from the bottom. The 
individual fish were in easy motion, both verti- 
cally and horizontally, but the aggregation as a 
