Drifting Object and Pelagic Fish — Gooding and Magnuson 
489 
grouped as transients, visitors, or residents 
(Table 1) on the basis of their reaction to the 
raft and the length of time they remained near 
it. Transients (many of which were flyingfish, 
Exocoetidae) did not appear to react to the raft, 
but were usually visible only momentarily as 
they swam by. Visitors did not aggregate at the 
raft, but appeared to react to it; they usually 
remained near it for several minutes to an hour. 
Residents aggregated at the raft; some stayed 
in view more or less permanently, and others 
swam out of view for several hours but usually 
returned. Different individuals of certain species 
did not always react in the same way to the raft; 
these species were consequently placed in more 
than one category. 
Residents were of two types: smaller fishes 
which stayed in the immediate vicinity of the 
raft and were usually in view of the observer; 
and iarge carnivores that were frequently out of 
view for several hours. When reappearing after 
a prolonged absence, the individual or group 
could often be identified by distinguishing 
characteristics such as abrasions, parasites, scars, 
the number in the group, and body size. The 
relation of all resident species to the raft was 
facultative, since each also occurs independently 
of any association with drifting objects. 
Small resident fishes were: freckled drift- 
fish, Psenes cyanophrys (Cuvier) ; juvenile pilot- 
fish, Naucrates duct or (Linnaeus); rough trig- 
gerfish, Canthidermis maculatus (Bloch) ; 
scrawled filefish, Alutera script a (Osbeck) (but 
only individuals exceeding about 20 cm, smaller 
ones behaving as visitors); amber jack, Seriola 
rivoliana Cuvier and Valenciennes; juvenile 
greater amber jack, Seriola dumerili (Risso) ; 
juvenile jack, Caranx sp.; adult and juvenile 
mackerel scad, Decapterus pinnulatus (Eydoux 
and Souleyet) ; juvenile skipjack tuna, Katsu- 
wonus pelamis (Linnaeus); juvenile yellowfin 
tuna, Thunnus albacares (Bonnaterre) ; juvenile 
dolphin, Coryphaena sp.; and juvenile stages 
of four reef fishes — damselfish, Abudefduf 
abdominalis (Quoy and Gaimard) ; sea chub, 
Kyphosus cinerascens (Forskal); goatfish, Mul- 
loidichthys samoensis Gunther; and squirrel- 
fish, Holocentridae. 
The large predatory residents were: dolphin, 
Coryphaena hippurus Linnaeus; wahoo, Acan- 
thocybium solandri (Cuvier) ; rainbow runner, 
Elagatis bipinnulatus (Quoy and Gaimard) and 
whitetip shark, Carcharhinus longimanus, usu- 
ally accompanied by adult pilotfish and remoras, 
Remora remora (Linnaeus). 
The freckled driftfish was by far the most 
common resident in both drift areas. On all 
drifts it was the first to appear, had the highest 
rate of accumulation (Table 2), and attained 
the largest population. At the end of the second 
equatorial drift, 729 were caught in the purse 
seine and several hundred escaped. Many were 
also caught at the end of other drifts. Freckled 
driftfish usually came to the raft singly or in 
small groups. Once a green turtle, Chelonia 
mydas, came to the raft accompanied by nine 
driftfish and one remora. The turtle left with 
the remora after a few minutes, but the drift- 
fish remained with the raft. 
Residents accumulated more rapidly by day 
than by night. Statistics on the average rate of 
accumulation of some of the more common 
residents appear in Table 2. Less common resi- 
dents, not listed in Table 2, also accumulated 
more rapidly by day than by night. 
Species composition differed between the 
Hawaiian and equatorial areas. Only 38% of 
the 27 fish identified to species in Table 1 were 
seen in both areas. Three of the more common 
species off Hawaii, the rough triggerfish, dol- 
phin, and damselfish, were either absent or rare 
in the equatorial waters. Of species that were 
residents at some stage in their life history, 
62% were common to both areas, whereas none 
listed only as a visitor was common to both 
areas. Some of the apparent differences between 
the areas could have resulted from differences 
in the time of year or could even be attributable 
to the sample sizes. For example, the occurrence 
of rainbow runners, pompano dolphin ( Cory- 
phaena equiselis Linnaeus), and green turtles 
in the equatorial but not the Hawaiian area may 
well be irrelevant, for all are common in 
Hawaiian waters. 
ADAPTIVE SIGNIFICANCE 
Our observations provided relevant informa- 
tion on the hypotheses that floating material 
(1) provides protection from predators, (2) 
concentrates the food supply, and (3) acts as a 
cleaning station. These hypotheses, of course, 
