Table 2.--Catch rates of yellowfin tuna by season and area 

Area or season 
Long. 132° W. 

Between summer 1957 and 
winter 1956 
Between long. 132° 
and 150° W. 
Summer 1957 
Between summer 1957 
and winter 1956 
Marquesas Islands 
Between Marquesas Islands 
and long. 132° W. 
Winter 1956 
Among Marquesas Islands 
long. 132° and 150° W. 
Summer 1957 





CATCH PER 100 HOOKS 

Figure 3.--Catch rates for tuna 
(number of 
yellowfin 
fish per 100 hooks) at the in- 
shore stations. 
The daily catch rates (fish per 100 hooks) of 
yellowfin tuna at inshore stations near the Mar- 
quesas Islands are presented in figure 3. The 
catch rate varied considerably from day to day 
(0 to 8.4 fish per 100 hooks). Seasonally yel- 
lowfin tuna were relatively abundant during the 
summer (table 2). The catch rates during the 
winter ranged from 0 to 2.2 fish per 100 hooks, 
but in the summer the range was 0.9 to 8.4. The 
Hawaiian longline fishery also shows a season- 
ality in abundance; greatest numbers are caught 
from May to September (Otsu, 1954). June 
(1953) suggested that the longline fishery in 
Hawaii is based on a spawning migration, for 
the months which have the highest catch rates 
for yellowfin tuna coincide with the period of 
greatest ovarian maturity. No comparable data 
On maturity are available from the Marquesas 
Islands. The occurrence of fish larvae, how- 
ever, has been taken to indicate spawning areas 

Comparison of catch rates Test Result 
Mann-Whitney U = 35.5, n, = ll, n 

=" 135) py <0 002 
1 2. 
do UR= 7565 ny 13% ny = 15; p <0.002 
do U = 4, n Seay ny = 9; p <0.002 
do Lue sil n, = a5 ny = 25) 5D) 0.421 
Reveral= X-.= 12.5078, d.f. = 2: pezonom 
Wallis 
and seasons by many workers, e.g., Matsumoto 
(1958). The abundance of yellowfin tuna larvae 
was observed during the periods covered by our 
longline fishing. Strasburg (1960) gave data on 
larvae captured in 1/2-hour surface plankton 
tows in an area around the Marquesas Islands 
bounded by lat. 7°32’ and 12°48’ S., long. 134°46’ 
and 143°55’ W. The larvae were captured at 
the rate of 0.02 per 1,000 m.° of water strained 
and 1.65 per 1,000 m.° of water 
strained in summer. Furthermore, as will be 
shown later, the higher catch rates on longlines 
in summer may have resulted from an influx of 
larger, and presumably more mature, yellowfin 
tuna into the Marquesas area. They well may 
converge on this area to spawn during summer. 
Strasburg (1958: p. 348) noted several ways 
in which the proximity of land can influence the 
distribution of marine animals: ‘‘For certain 
oceanic species the presence of land acts only 
as a barrier to movements, whereas others 
congregate about islands and other land masses 
to feed or to reproduce. It occasionally happens 
that oceanic fish abound in insular environ- 
ments, either because of the islands’ intrinsic 
nutritive richness or because they lie in the 
path of rich oceanic currents.”’ 
My data, although rather meager, provide 
information on the abundance of yellowfin tuna 
close to the Marquesas Islands as contrasted 
with the adjacent oceanic areas, For this com- 
parison, the oceanic stations south of lat. 7° S. 
were selected. I believe that the effect of the 
equatorial enrichment system, in which yellow- 
fin tuna are known to be relatively abundant, is 
not discernible this far south. During summer, 
the average catch rates were higher in the in- 
shore waters of the Marquesas than in the ad- 
in winter 
