FISHERY BULLETIN: VOL. 74, NO. 1 



and effort data were also collected routinely at 

 the cannery by personnel of the Honolulu 

 Laboratory, National Marine Fisheries Service. 

 The cannery records, however, were deficient in 

 that they did not provide information on vessels 

 not returning to Kewalo Basin, where the can- 

 nery is located, on vessels based on neighboring 

 islands, or on the area of operation. 



Catch Reports of 1948-64 



The forms for reporting skipjack tuna catch 

 have been revised several times over the years. 

 Essentially, all the different versions used in 

 1948-64 had spaces for recording the date of land- 

 ings, the amount of skipjack tuna landed, and the 

 area fished. The date of landing represented an 

 effective trip that may have lasted from one to 

 several days. Because Hawaiian vessels have 

 limited cruising range, a trip usually lasts 1 day. 

 Studies of interview data collected in 1960 

 showed that of 329 effective trips, 315 or 96% 

 lasted 1 day (Uchida 1967). 



Catch Reports of 1965-70 



The catch report forms of 1965-70 provided 

 spaces for recording not only the amount of skip- 

 jack tuna caught and the area fished, but also the 

 date of each day spent on the fishing ground, a 

 zero catch when no fish was caught, and the 

 number of men aboard per trip. Each entry repre- 

 sented 1 day's fishing. In using data for these 

 years, therefore, days with catches were assumed 

 to be equivalent to effective trips. The sum of 

 days with and without catches was taken as the 

 total number of days fished. 



Reporting of Zero-Catch Trips 



Review of catch reports and cannery records for 

 1965-70 showed that some vessels occasionally 

 failed to report zero-catch fishing days. When the 

 number of zero-catch trips recorded in the can- 

 nery records exceeded that reported in the catch 

 reports, the difference was assumed to be the 

 number of unreported zero catches. Most vessels 

 reported more zero catches in the catch reports 

 than were recorded in the cannery records; pre- 

 sumably, trips were not recorded at the cannery 

 when a vessel did not return to home port. These 

 catch reports were assumed to be accurate. 



Not all unreported zero-catch days were ac- 



counted for. In a few cases, vessels failed to indi- 

 cate a zero catch in the catch report after an un- 

 successful day of fishing and also failed to return 

 to Kewalo Basin, site of the cannery and home 

 port of the Honolulu-based fleet. Then, neither 

 the catch report nor the cannery record showed 

 the effort expended. 



For Honolulu-based vessels, unreported zero- 

 catch days in 1965-70 varied between 0.5 and 

 3.8% of the estimated annual number of days 

 fished (Table 1). Differences between reported 

 and estimated number of days fished were not 

 significant it = 1.020; df = 5;P = 0.36); therefore 

 the few zero-catch days that went unreported 

 should not seriously affect the data in this study. 



Table l. — Total days fished as reported, estimated number 

 and percentage of zero-catch days not reported, and esti- 

 mated total days fished by Honolulu-based Hawaiian skipjack 

 tuna fishing vessels, 1965-70. 



SOURCES OF VARIABILITY IN 

 FISHING POWER AMONG VESSELS 



Fishing power is usually calculated on the 

 basis of a physical feature of the vessel such as 

 gross tonnage or engine horsepower. Differences 

 in fishing power, however, are certainly more 

 complicated than a comparison of these physical 

 attributes. Rothschild (1972) stated that "A con- 

 siderable portion of the variability in fishing 

 power among fishing units can be attributed to 

 variability in skill of the fishing skipper." Fishing 

 skill cannot be measured easily, but its influ- 

 ence on the fishing power of the vessels should 

 be understood. 



Variability in crew size from trip to trip also 

 complicates the comparison of fishing power 

 among the vessels. For example, catch reports 

 showed that crew size in 1970 varied between 5 

 and 11 men per trip. Frequently, small vessels 

 were fully crewed while large vessels operated 

 shorthanded. The result was that some of the 

 small vessels were outperforming the larger ones 

 in some years. 



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