Distribution and Ecologic Aspects of Central Pacific 
Salpidae (Tunicata ) 1 
James L. Yount 2 
The present report is a continuation of a 
general salp study, the first section of which 
already has been reported (Yount, 1954). It 
concerns the distribution and ecology of the 
salps collected during two cruises by the 
"Hugh M. Smith” of the Pacific Oceanic 
Fishery Investigations of the United States 
Fish and Wildlife Service (referred to in the 
remainder of this report as POFI) in the 
central Pacific Ocean. Nineteen out of a total 
of 22 recognized world species were found in 
these collections. 
Knowledge of the distribution of salps was 
reviewed by Traustedt (1885), Apstein (1894, 
1906), Metcalf (1918), Ihle (1935), and 
Thompson (1948). Various other investiga- 
tors have added to this general knowledge in 
regard to certain species. Certain points in 
regard to geographic distribution, however, 
needed clarification. Among these was an in- 
vestigation of the usefulness of salps as in- 
dicator species of oceanic currents within the 
area of study. Moreover, knowledge of sea- 
sonal effects on salps, of the relation of salp 
abundance to the abundance of other zoo- 
plankton, and of the relation of salp abun- 
dance to physicochemical environmental 
factors was very limited. Thus studies were 
1 Contribution No. 99, Hawaii Marine Laboratory, 
in cooperation with the Department of Zoology and 
Entomology, University of Hawaii. Part of a thesis 
submitted to the Department of Zoology, University 
of Hawaii, in partial fulfillment of the requirements for 
the degree of Doctor of Philosophy. 
2 Department of Biology, University of Florida, 
Gainesville, Florida. Manuscript received August 27, 
1956. 
carried out, insofar as the available data 
would permit, in an attempt to elucidate 
these points. In addition, little information 
exists defining the actual role or position of 
salps in the plankton community (the niche 
as defined by Elton, 1927) ; consequently, the 
niche of the different salp species was inves- 
tigated as thoroughly as possible. 
ACKNOWLEDGEMENTS 
I wish to express my gratitude to R. W. 
Hiatt and L. D. Tuthill for their help through- 
out this investigation. O. E. Sette of POFI, 
in addition to permitting me to use the plank- 
ton collections, reviewed the manuscript in 
part. I also wish to thank T. S. Austin of 
POFI for his help with regard to the section 
Physicochemical Factors of the Environment. J. 
E. King of POFI helped by furnishing in- 
formation on total plankton volumes and 
numbers of the collections examined. 
MATERIALS AND METHODS 
The animals used were taken from a large 
series of plankton captures made by POFI in 
an area that extended from 27° N. to 15° S. 
and from 176° W. to 155° W. In this area, 
the "Hugh M. Smith" made cruise 5 in June, 
July, and August of 1950, and cruise 8 in 
January, February, and March of 1951, thus 
permitting seasonal comparisons. The study 
of abundance and distribution was confined 
to cruises 5 and 8; of these cruises, all samples 
(51) from cruise 5, and 30 samples out of 106 
from cruise 8, were studied. 
Ill 
