Table 2. — Estimated total inshore and total offshore catches of 

 skipjack tuna in Hawaiian waters, 1952-6$ 



Year 



1952. 

 1953. 

 1954. 

 1955 

 1956 

 1957. 

 1958. 

 1959 

 1960 

 1961 

 1962 



Estimated 



offshore 



catch 



Thousand 

 pounds 

 1,750 

 4,100 

 5,188 

 1.648 

 3.006 

 1.220 



957 

 2.110 



736 

 2.397 

 1.695 



average and good years the inshore catch 

 averaged 75 percent. 



Yamashita (1958) who examined the 1948- 

 53 catches of skipjack tuna suggested that 

 about 8.0 million pounds may be nearly the 



Q 4 



o 

 a. 



S 



.J 



^ 8 



^H lUIAL I.AI«.n 



INSHORE CATCH H 



iiiiiidni 



OFFSHORE CATCH 



1952 I9S3 I9,S1 1955 1956 1957 1958 1959 1960 196J 1962 

 YEAR 



Figure 1. — Total catch of skipjack tuna (all areas) 

 and the estimated inshore and offshore catches in the 

 Hawaiian fishery, 1952-62. 



184 



maximum that can be obtained in the inshore 

 area. The present study indicates, however, 

 that the inshore catch can be well above this 

 level. The 1959 landings, for example, were 

 10.3 million pounds and were caught by a fleet 

 of 21 full-time vessels, although in 1949-53 

 26 to 28 vessels were fishing full time for skip- 

 jack. 



The offshore catch increased gradually from 

 1.8 million pounds in 1952 to a peak of about 

 5.2 million pounds in 1954 (fig. 1). After a 

 sharp decline to about 1.6 million pounds in 

 the following year, the offshore take fluctuated 

 between 0.8 and 3.0 million pounds from 1956 

 to 1962. 



FISHING INTENSITY 



Fishing intensity is the total amount of ef- 

 fort expended in catching fish. Eflfort changes 

 with time in difl'erent ways. For example, in a 

 fishery where a trip is considered a unit of 

 fishing eflfort, an increase in the duration of 

 trips or an increase in the fishing power of 

 vessels alters the unit of effort. These changes 

 complicate the analysis of catch and eflfort 

 data ; therefore it becomes necessary to obtain 

 and examine information on size of vessels, on 

 modification of or improvement to fishing gear, 

 and on changes in fishing time. 



SIZE CLASSES OF VESSELS 



It may be expected that size of a vessel in- 

 fluences its potential eflficiency as a fishing unit 

 in a pole-and-line flshery because the larger 

 crews give the larger vessels greater flshing 

 power. One measure of effort is the number 

 of men aboard per trip ; this number may vary 

 among vessels and with the years. The inter- 

 view records for 1950-56 indicated that the 

 number of men aboard per trip varied between 

 6 and 14. 



The eflfects of this crew variability were 

 reduced by separating the vessels arbitrarily 

 into two size classes according to their bait- 

 carrying capacities. The bait-carrying capacity 

 was a good measure of the vessel's fish capac- 

 ity, because on the return to port the empty 

 baitwells were used to store the catch. The 

 vessels with large bait capacities were the 

 large ones that usually carried more men. Data 



SKIPJACK IN HAWAIIAN WATERS 



