Longline Fishing for Deep-Swimming 
Tunas in the Marquesas Islands 
and Adjacent Areas 
By 
HOWARD O. YOSHIDA, Fishery Biologist 
Bureau of Commercial Fisheries Biological Laboratory 
Honolulu, Hawaii 96812 
ABSTRACT 
Six hundred forty-two tuna, including 438 yellowfin tuna (Thunnus albacares), 
102 bigeye tuna (T. obesus), 
51 albacore (T. alalunga), and 51 skipjack tuna 
(Katsuwonus pelamis), were caught by longline fishing on three cruises across 
and around the Marquesas Islands (ca. 
the Equator on long. 132° and 150° W. 
long. 140° W.) between August 1956 and May 1958. 
These cruises were part of 
an investigation of fishery resources of the Marquesan area by the Bureau of 
Commercial Fisheries Biological Laboratory at Honolulu, 
The distribution and abundance of yellowfin tuna are considered in greatest 
detail in this report, because this species dominated the catches. 
Yellowfin tuna 
were more abundant during the Southern Hemisphere summer than winter and on 
long. 132° W. than on long. 150° W.; also, they were more numerous in the 
“‘inshore,’’ <148 kilometers (80 nautical miles) from land, waters of the Mar- 
quesas than in the adjacent ‘‘oceanic’’ (>148 kilometers from land) waters. 
Their abundance differed seasonally in the insular waters of the Marquesas. 
Although bigeye tuna were not as abundant nor as widely distributed, their 
distribution was somewhat similar to that of yellowfin tuna. 
No albacore were caught north of lat. 7° S. on long. 132° and 150° W. This 
distribution appeared to be associated with a discontinuity of the oceanic struc- 
ture extending east-west around lat. 10° S, 
INTRODUCTION 1955; Shomura and Murphy, 1955). 
Later in- 
Investigations of the high-seas fishery re- 
sources of the tropical and subtropical Pacific 
Ocean by the Bureau of Commercial Fisheries 
Biological Laboratory at Honolulul/ have in- 
cluded sampling of deep-swimming tunas taken 
by longline in equatorial waters. The early 
investigations were designed to cover a vast 
area of the equatorial Pacific to delimit the 
general distribution and abundance of the deep- 
Swimming tunas, This exploratory fishing 
revealed a concentration of yellowfin tuna 
(Thunnus albacares) along the Equator, with a 
zone of high abundance between long. 140° and 
160° W. (Murphy and Shomura, 1953a, 1953b, 
1/ 
— Formerly known as the Pacific Oceanic Fishery 
Investigations (POFI). 
vestigations were centered on the distribution 
and abundance of yellowfin tuna around the Line 
Islands (Iversen and Yoshida, 1956, 1957), which 
are located within the general zone of high 
abundance. 
After the completion of the investigations in 
the central equatorial Pacific, exploratory fish- 
ing was extended to the Marquesas Islands and 
adjacent areas, The longline fishing in this 
region, however, was ancillary to a more inten- 
sive study of the surface tunas. In addition, a 
small part of the fishing was expended towards 
testing certain hypotheses that had developed 
from results of previous work in the central 
equatorial Pacific. 
There were three cruises to the Marquesas 
between August 1956 and May 1958 during which 
at least part of the time was spent in longline 
