Table 3. — The lotaJ catch, number of Class 1 and Class 3 

 vessels sampled, their total recorded trips, and number and 

 percentage of zero-catch trips, Hawaii, 1957-59 



Because no additional data are available, I as- 

 sumed that this sample represents the fleet's 

 activities for these years. 



Zero-catch trips were more frequent among 

 Class 2 than among Class 1 vessels (table 3). 

 The higher rate of occurrence in poor years 

 (1957-58) than in the good year (1959) indi- 

 cates that the percentage of zero-catch trips 

 tends to decrease as total catch increases. The 

 apparent negative correlation between these 

 variables is supported to some extent by Ship- 

 pen (1961: table 2) who analyzed the logbooks 

 of two vessels. (The original records show 

 that these were Class 2 vessels.) He found 

 that in a poor year (1952), zero-catch trips ac- 

 counted for 10 percent of the total trips made 

 by Boat A and 14 percent of those made by 

 Boat B. In a good year (1953), zero-catch 

 trips were 8 and 10 percent for Boat A and 

 Boat B, respectively. 



The numbers of effective trips and zero-catch 

 trips were used to estimate the total effort for 

 1957-59. For example, in 1957, the total num- 

 ber of zero-catch trips among Class 1 vessels 

 was estimated by simple proportion to be 262. 

 The estimated total effort for both size classes 

 for 1957-59 is given in table 4. 



The number of zero-catch trips was large in 

 1957 and 1958. In 1957 the estimated total 

 number of unreported zero-catch trips was 822, 

 or an average of about 33 per vessel ; in 1958 

 the estimated number was 502 or about 21 

 per vessel. In 1959, a good year in the fishery, 

 the estimated number of zero-catch trips for 

 the fleet was only 128 — about 6 per vessel. 



The results indicate that catch per effective 

 trip should be regarded with caution. Effective 

 effort is a biased measure of fishing pressure, 

 but it has been used becau.se information on 

 zero-catch trips was not available from the 

 catch reports used. This condition has been 

 remedied ; in July 1964, the Hawaii Divisi()n 

 of Fish and Game issued revised catch-report 

 forms which have spaces for recording zero- 

 catch trips. 



DURATION OF AN EFFECTIVE T^IP 



Most of the vessels in the fleet made short 

 runs. They left for the fishing grounds in the 

 early morning and returned to port in the 

 evening. On occasion, however, trips of 2, 3, 

 or 4 days have been recorded. Only a small 

 proportion of the day was devoted to actual 

 fishing ; the greater part was spent scouting 

 for bird flocks that follow schools of skipjack 

 tuna. 



To judge the possible effects of longer trips, 

 the frequency of occurrence of 1- and multiple- 

 day trips (2 or more days per trip) was de- 

 termined from 1960 interview records for 16 

 vessels (table 5). Records for a total of 329 

 trips showed 315 of 1 day (95.7 percent), 13 

 of 2 days (4.0 percent), and 1 of 3 days (0.3 

 percent). Of the thirteen 2-day trips, 9 had 

 catches during both days at sea, but each of the 



Table 4. — Xumlier of effective trips and estimated number of 

 zero-catch trips of Class 1 and Class 2 vessels, Hawaii, 1957-59 



Table 5. — Xumber and percentage of /-, 2-. and S-dnij trips, 

 total catch, catch per effective trip, and range of catches of 16 

 Hawaiian skipjack tuna vessels in 1960 



186 



SKIPJACK IN HAWAIIAN WATERS 



