remaining 4 had only 1 day in which skipjack 

 tuna were caught. We may conclude that a trip 

 usually represents 1 day's fishing. 



AVERAGE NUMBER OF MEN HOOKING PER 

 EFFECTIVE TRIP 



The number of hooks fishing on a Hawaiian 

 skipjack tuna vessel depends on the number of 

 fishermen that take fishing positions along the 

 stern during the fishing operation, since each 

 man fishes a single pole to which a line and 

 feathered jig is attached. Yuen (1959), in a 

 study of the response of skipjack tuna to live 

 bait, pointed out that the number of men 

 hooking was one of the factors that affect the 

 catch per school. The catch per effective trip 

 is also related to the number of men hooking ; 

 it is important, therefore, to examine the year- 

 to-year variation in this number. Data on the 

 number of men hooking were available only 

 from records collected between 1950 and 1960 ; 

 those for 1950-56 and 1960 were from inter- 



Tabi.e 6. — The monthly and annual average of the number of 

 men hooking per effective trip on Class 1 and Class 2 Hawaiian 

 skipjack tuna vessels, 1950-60 



view records and those for 1957-59 were from 

 logbooks. These data were used to calculate 

 monthly and annual averages by size classes of 

 vessels (table 6). 



I expected that the number of men hooking 

 per effective trip would be greater during the 

 season months (May to September) than dur- 



ing the off-season months (Shippen, 1961). 

 Despite the incompleteness of the data for 

 some years, the trend of change, discernible 

 from the data for those years where informa- 

 tion was adequate, indicates no pronounced in- 

 crease in the number of men hooking in May to 

 September (fig. 3). More men fished per ef- 



JAN: .\UR may JUl-T SEPT. 

 MONTH 



JAN ,M-\R ,M,\y JULY SFPT- NOV 

 .MO.N'TII 



Figure 3. — Monthly averages of number of men hook- 

 ing per effective trip on Class 1 and Class 2 

 Hawaiian skipjack tuna vessels, 1950-60. Class 1 

 vessels, broken line; Class 2 vessels, solid line. 



fective trip in Class 2 than in Class 1 vessels, 

 although the 1959-60 data indicate that the 

 differences between the two classes were small. 

 Figure 4 illustrates the decline in the annual 

 average. The average number of men hooking 

 per effective trip on Class 1 vessels was fairly 

 steady from 1950 to 1955, then dropped and 

 remained at a lower level in 1956-60. The 

 average for Class 2 vessels declined almost 

 steadily from 1950 to 1960. This decrease in 

 the number of men hooking from 1950 to 1960 

 was not, however, accompanied by a decline in 

 the catch per effective trip. An explanation is 

 given in the section on Apparent Abundance. 



U.S. FISH AND WILDLIFE SERVICE 



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