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NORTH LATITUDE 



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S- LATITUDE -N 



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 S- LATITUDE- N 



three north-south lines in the eastern and central 

 Pacific. On this cruise 6- and 11 -hook gear was 

 fished simultaneously; therefore, 6-hook catch 

 rates have been converted to 1 1 -hook equivalents 

 and averaged with the 1 1 -hook catch rates. The 

 variation of yellowfin catches with latitude and 

 temperature is shown in figure 4. The first 

 series on 119°W. longitude extending from 33°N. 

 to 20°N. latitude yielded no yellowfin. The sec- 

 tion on 110°-115°W. longitude, from 10°N. to 

 10°S. latitude produced the best catches (>2 

 yellowfin per 100 hooks) between 6°N. and 1°S. 

 latitude. Runningnorth on 155°W. longitude the 

 highest catch rates ( >2 yellowfin per 100 hooks) 

 were made between 2°S. and 3°N. latitude. Most 

 of these stations were outside the influence of 

 land (more than 60 miles) so that the catch rates 

 are readily comparable with previous results 

 from the open ocean. The results f r o m along 

 the Equator are consistent with past experience. 

 Shomura and Murphy (1955) found that the center 

 of abundance of yellowfin at several longitudes 

 was at or a little north of the Equator during 1953. 



Longitudinal Variation 



The Japanese carried out extensive long- 

 line fishing in the equatorial Pacific during 1954. 

 Records of their catches are available (Nomura 

 1954-55) for each month of the year. It is dif- 

 ficult to compare these data with ours because 

 the Japanese in general fished farther to the 

 north during many months of the year (probably 

 in search of better bigeye catches) than did U. S. 

 fishermen or the POFI research vessels. Never- 

 theless, certain aspects of seasonal and geo- 

 graphic variation are susceptible to analysis. 



The catch rates of American and Japanese 

 vessels are plotted in terms of 6-hook gear for 

 each month of the year in figure 5 for latitudes 

 11°S. to 10°N. (Table 18 in the Appendix lists 

 the results of the Japanese fishing. ) Consider- 

 ing the Japanese data for the area west of 170°W. 

 longitude, the seasonal trend in catch rates is 

 the same as described by Shomura and Murphy 

 (1955), i.e. , low catch rates, less than 2 yellow- 

 fin per 100 hooks from January to May, slightly 

 higher catch rates in June and July of 2-4 yellow- 

 fin per 100 hooks, with a decrease again from 

 August to December to less than 2 yellowfin per 

 100 hooks. 



Figure 4. - -Variation of yellowfin catches with 

 latitude and temperature on three station lines 

 along 119°W. , 110°-115°W. , and 155°W. longi- 

 tude; Charles H. Gilbert cruise 15, February 

 to April. /If no yellowfin were taken a zero 

 is shown at that latitude. / 



In comparing the catches west of 170°W. 

 with those of the Line Islands area during 1953, 

 Shomura and Murphy ( 1955) found evidence of an 

 east-west shift in the equatorial yellowfin popu- 

 lation- During 1954 there was some indication 

 of a similar shift in the center of abundance. 



