1953 1953 1954 1955 I95G 1957 1958 1959 1960 1961 1962 

 YKAR 



Figure 7. — Total catch and catch per effective trip by 

 areas for Class 1 and Class 2 Hawaiian skipjack 

 tuna vessels, 1952-62. 



nificantly correlated with the total catch 

 (r = 0.762; df = 9; p<0.01, and r = 0.697; 

 df = 9; p = 0.02, respectively) . 



FACTORS AFFECTING ESTIMATES OF THE CATCH 

 PER EFFECTIVE TRIP 



Proper interpretation of statistics on catch 

 and effort requires information about factors 

 that contribute to variations in catch per unit 

 of effort. For the skipjack tuna fishery in 

 Hawaii, a number of factors have been isolated 

 as causes of variation in catch per effective 

 trip. Some of these are discussed here. 



Changes in the Availability of Skipjack Tuna 



In a study on the oceanography and skipjack 

 fishery in the Hawaiian region, Seckel and 

 Waldron (1960) pointed out that the time of 

 initial warming of the surface water at Koko 

 Head, Oahu, appears to be related to the annual 

 skipjack landings. When the initial warming 

 occurred in February, this implied that the 

 California Current System was well developed 

 and average or better-than-average fishing 

 years occurred. When the initial warming oc- 

 curred in March, fishing was poor. 



The relation between the time of initial 

 warming and skipjack landings later in the 



season appeared to have some predictive value 

 concerning the availability of skipjack tuna. 

 According to Seckel (1963: fig. 4), the initial 

 warming occurred in March in 1952, 1955, 1957, 

 1958, and 1960 ; skipjack availability should be 

 low during these years. As was pointed out 

 earlier, however, the catch in 1955 was close 

 to the average catch of 9.7 million pounds for 

 1952-62 (table 1) and was considered an av- 

 erage year for the purpose of this report. The 

 forecasts made from 1959 to 1962 were de- 

 pendable, but the prediction of favorable fish- 

 ing conditions and catch levels could not be 

 made with assurance because only partial 

 understanding of the relation has been 

 achieved. At present, variations in skipjack 

 availability appear to be one of the most im- 

 portant factors causing fluctuations in the total 

 catch of skipjack in the Hawaiian fishery. 



Changes in the Number of Men Hooking and in 

 Fishing Technique 



Since the average number of men hooking 

 per effective trip declined between 1950 and 

 1960, I examined the data to .see if the Y/g 

 showed a similar decline. The results (table 

 9 and fig. 7) showed that Y/g did not decline 

 during 1952-62. For example, if the poor years 

 of 1952, 1957, 1958, and 1960 are omitted to 

 simplify the comparison, Y/g for the remaining 

 years appears to be approximately the same 

 before and after 1955, that is, no indication 

 exists of a decline in Y/g. An excellent 2-year 

 comparison is provided by the data of both 

 size classes in 1954 and 1959, in which years 



T.Mii.F, 9. — The catch per ejfeclive trip of Class 1 and Class 2 

 Hawaiian skipjack tuna vessels in inshore and offshore 

 areas, 1962-62 



190 



SKIPJACK IN HAWAIIAN WATERS 



