Observations on the Ecology of Four Apogonid Fishes 
Donald W. Strasburg 1 
The fishes of the family Apogonidae are 
small, inconspicuous creatures which live in 
and around coral reefs. In the atolls of the cen- 
tral Pacific they are common, occasionally color- 
ful, and sometimes occupants of specialized 
habitats. This paper reports aspects of the 
ecology of four species which are uncommon in 
collections: Apogon novaeguzneaeVAencienn.es, 
which lives among the spines of the sea urchin 
Echinothrix diadema (Linnaeus) ; Apogon lep- 
tacanthus Bleeker, which occurs in vast shoals 
associated with the coral Montipora gaimardi 
Bernard; and Apogon gracilis (Bleeker) and 
Gymnapogon gracilicauda Lachner, which 
school in open water over reefs. Observations 
were made in the Marshall Islands during the 
summers of 1950, 1951, and 1955, when the 
writer participated in research projects spon- 
sored by the Office of Naval Research, the Uni- 
versity of Hawaii, and the Pacific Science Board 
of the National Research Council. Thanks are 
due these institutions as well as to the Military 
Air Transport Service and the Atomic Energy 
Commission who supplied transportation and 
many facilities. I also wish to thank Mme. I. 
Catala (Noumea Aquarium, New Caledonia), 
Dr. D. B. E. Magnus (Zoologisches Institut, 
Darmstadt, Germany), Dr. C. L. Smith (Amer- 
ican Museum of Natural History, New York), 
Dr. R. A. Stevenson (University of Puerto 
Rico), and Mr. G. P. Whitley (Australian 
Museum, Sydney) for supplemental data. 
Apogon novae guineae Valenciennes 
Visits were made to a number of atolls in the 
Marshall and Gilbert groups, but A. novae - 
gzzineae was found only at Eniwetok in the 
northern Marshalls. Here it occurred in the 
lagoon off Parry and Japtan Islands, and on the 
shallow ocean reef northwest of Cochiti Island. 
The fish was seen on 33 occasions, 23 times 
1 Bureau of Commercial Fisheries Biological Labo- 
ratory, Honolulu, Hawaii. Manuscript received De- 
cember 10, 1964. 
among the spines of the poisonous sea urchin 
Echinothrix diadema, and 10 times nowhere 
near an urchin. Both the fish and urchins lived 
in caves or beneath ledges, neither occurring in 
less than 4-ft depths and most living between 
about 8 and 18 ft. The number of fish per 
urchin ranged from 3 to 12, with 4 or 5 being 
usual. 
Another apogonid, Paramia quinquelineata 
(Cuvier) sometimes accompanied A. novae - 
guineae among the urchin spines, while several 
other species were found in urchins lacking 
novae gzzineae. These were Apogon jraenatus 
Valenciennes, Apogon savayensis Gunther, 
Apogon novemfasciatus Cuvier, and the pipe- 
fish Doryrhamphus m. melanoplezzra (Bleeker) . 
The occurrence of these four fishes among 
urchin spines was uncommon and usually in- 
volved only one or two individuals in a par- 
ticular urchin. The attitude of these spine- 
dwelling species was horizontal except for 
Doryrhamphus, which oriented parallel to the 
nearest spines with its head toward the urchin’s 
test. 
Most of the above spine-dwelling fishes bear 
lengthwise stripes, the exception being A. 
savayensis. This is a drab species which neither 
matches nor contrasts with the urchin and prob- 
ably occurs among its spines only occasionally. 
A. novaeguineae, on the other hand, is one of 
the most brightly colored apogonids, and its 
brilliant yellow contrasts vividly with the black 
or deep red of the urchin. 2 Its stripes are in- 
2 A description of the color of living novaeguineae 
could not be found in the literature and therefore is 
presented here. Ground color of body light yellow, 
with gold and silver iridescence on sides of head and 
trunk. Throat and gill membranes white, rest of head 
yellow with scattered dusky pigment, giving it a dirty 
appearance. Five narrow white lines on head and 
body: first from occiput to first dorsal, where it bifur- 
cates and runs along dorsal bases to caudal peduncle; 
second from interorbital along top of head and trunk 
parallel to first, uniting with its mate on dorsal edge 
of caudal peduncle; third from tip of snout across iris, 
338 
