UCHIDA: REEVALUATION OF FISHING EFFORT 



Table 5. — Catch per day fished inshore and offshore among class 1 and class 2 

 vessels, class 1 efficiency factors, and their geometric mean, 1948-70. 



where TCi = total catch of class 1 vessels, 

 TC2 = total catch of class 2 vessels, 

 EF = efficiency factor, 

 DFi = days fished among class 1 vessels, 



and 

 DF2 = days fished among class 2 vessels. 



In 1948-70, C/SDF of skipjack tuna in Ha- 

 waiian waters ranged from a low of 1.61 MT in 

 1957 to a high of 3.29 MT in 1965, but no trend 

 with time was discernible (Table 6; Figure 6). 



Relative fishing intensity is estimated from 

 C/SDF and the total state catch, which includes 

 catches of part-time as well as full-time vessels: 



Relative fishing intensity — 



C/SDF 



where TC^ = total state catch. 



When examined over the 23-yr period, fishing 

 intensity did not decrease appreciably despite a 

 gradual decrease in the number of vessels fishing 

 from a maximum of 28 in 1951 to 15 in 1970. 

 With a reduction in the fleet, which occurred 

 primarily among the older class 1 vessels, fishing 

 intensity would be expected to decline, but it did 

 not. The reason was that the average days fished 

 per vessel per year increased. Class 1 vessels 



10 vessels and 121.2 days in 1959-70 when their 

 numbers further decreased from 8 to 4 vessels 

 (Figure 7). Class 2 vessels have not decreased in 

 number drastically, declining from 14 in 1955 to 



11 in 1970. Averaging 86.9 days fished prior to 

 1964, class 2 vessels subsequently averaged 119.8 

 days per year. 



INTERRELATION OF TOTAL 

 CATCH, FISHING INTENSITY, 

 AND APPARENT ABUNDANCE 



The total catch of skipjack tuna, given in Table 

 6 and shown in Figure 6, fluctuated with C/SDF 

 in a similar fashion in 1948-70 (r = 0.902; df = 

 21; P<0.01). For the years studied, then, total 

 catch may be satisfactory as a gross index of 

 changing apparent abundance but may not be 

 suitable in future years because it is obviously 

 sensitive to changes in demand or fishing effort, 

 competition from other fisheries, and economic 

 constraints upon the fishery. 



Changes in C/SDF are not associated with 

 changes in fishing intensity (r = 0.302; df = 21; 

 P>0.05); therefore, the apparent abundance of 

 skipjack tuna in Hawaiian waters is not 

 influenced by changes in the amount of fishing 

 effort expended, but by fishery-independent fac- 

 tors such as variations in availability, which in 

 turn is related to changes in the fishes' habits or 



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