offshore, but, on the other hand, the stations classed as insular may in 

 some instances be outside of any influence of the islands. 



Yellowfin Tuna 



In this section we shall consider variations in the location of 

 the center of abundance of oceanic yellowfin tuna in the central equa- 

 torial Pacific during 1953. We are somewhat handicapped because 

 sampling was not adequate over the entire area during most seasons. 

 There are, however, clear indications that the population is not static 

 in space, and there is on hand for 1953 enough information to develop 

 a preliminary hypothesis. 



The catch results presented graphically in figures 2 and 3 can 

 best be studied by considering the temporal changes in yellowfin abun- 

 dance first by longitude, then by latitude, and finally as an integrated 

 whole. 



In terms of longitude, during February and March yellowfin 



were more abundant (about 10 per hundred hooks) to the east (140 W.) 



than they were farther west (150 W. ) (fig. 2), where about 3 were 



taken per hundred hooks fished. Unfortunately, there is no information 



from west of 150 W. for this period, so there is no way of knowing 



whether the trend continued in that direction unless the poor catches 



o 

 in April near 180 are regarded as evidence that the trend did continue 



west (fig. 3). Later in the year, during May and June, catches of 9 

 yellowfin per hundred hooks were made along 150 W. , but the north- 

 south extent of the area of high catches was limited (only two stations), 

 while on 170 W. a much wider band of good fishing (around 7 per hun- 

 dred hooks) was found, suggesting that there were more yellowfin west 

 of 150 W. The concentration encountered on 170 W. evidently extended 

 at least as far as 180 , for Japanese commercial boats experienced 

 catches averaging over 5 yellowfin per hundred hooks between 170 W. 

 and 180 (fig. 3). During August the highest catches (about 10 per hun- 

 dred hooks) were made on 155 W. (fig. 2), and poorer fishing (less than 

 5 per hundred hooks) was found farther west between 160 W. and 180 

 (figs. 2 and 3), suggesting an eastward shift of the population from its 

 location during May and June. Finally, during December poor catches 

 (about 2 per hundred hooks, with one exception) were had along 155 W. 

 (fig. 2), but there is no information from areas east or west of that 

 longitude so we cannot hazard a guess as to the location of the center 

 of abundance, if one existed, along the Equator at that time. 



