skipjack tuna fishing is highly competitive in 

 Hawaii; therefore, fishermen are reluctant to 

 disclose the locations of their catches. Yama- 

 shita compared the catch localities given in the 

 catch reports with those obtained through inter- 

 views with the fishermen and found that the two 

 records agreed for only about 45 percent of the 

 trips examined. I, however, do not believe that 

 the catch localities recorded in the catch re- 

 ports are so erroneous; rather , information ob- 

 tained through interviews should be questioned. 

 The conditions under which the interview data 

 were collected and turned in did not ensure that 

 the data would remain fully confidential: it is, 

 therefore, likely that some fishermen gave er- 

 roneous information. Personal contacts and 

 discussions with fishermen have led me to be- 

 lieve that catch reports are reasonably reli- 

 able, because the captain or a crewmember re- 

 cords the actual catch and locality on the re- 

 port form after each trip. At the end of each 

 month, the original of the catch report is sent 

 to the Division of Fish and Game; a copy is re- 

 tained aboard the vessel as a permanent record 

 of its operations. 



ANALYTICAL PROCEDURES 



The procedures used to analyze the catch 

 statistics, which were described in detail by 

 Uchida (1967), are briefly discussed in the fol- 

 lowing sections, which deal with statistical area 

 system, size classes of vessels, and standardi- 

 zation of catch per effort. 



Statistical Area System 



The fishing ground in Hawaiian waters is di- 

 vided into three general areas (fig. 1). The 

 first extends from the coastline to just outside 

 the reefs, a distance of about 4 km., the second 

 extends from 4 to 37 km., and the third is be- 

 yond 37 km. from the coastline. These areas 

 are further subdivided into smaller statistical 

 areas, each with a three-digit code number. 

 The first digit represents counties within the 

 State; 1 and 2 refer to Hawaii County, 3 refers 

 to Maui County (also includes the islands of 

 Molokai, Lanai, and Kahoolawe), 4 refers to the 

 City and County of Honolulu, and 5 refers to 

 Kauai County (also includes the island of Nii- 

 hau). If the last two digits of the code number 

 are between 00 and 19, the area is within 4 km. 

 of the coastline; if they are between 20 and 39, 

 the area is between 4 and 37 km. of the coast- 



line; and if 40 or larger, the area is beyond 

 37 km. 



Catches within 4 km. are infrequent and in- 

 significant. These catches were therefore com- 

 bined with those from areas immediately off- 

 shore. For example, catches from area 306, 

 near Kahoolawe, were combined with those 

 from area 326, which is immediately offshore. 

 After combining, all areas within 37 km. of the 

 coastline were redesignated as inshore; those 

 beyond were called offshore. 



Size Classes of Vessels 



Hawaiian skipjack tuna fishing vessels vary 

 in fishing power because of differences in ves- 

 sel size, crew size, and bait-carrying capaci- 

 ties. Variability in fishing power necessitated 

 a separation of the vessels into two size classes 

 according to bait-carrying capacities. Class 1 

 vessels, manned by small crews and with ca- 

 pacities of less than 3,000 liters per baitwell. 

 range from 24 to 49 gross metric tons. Class 2 

 vessels, usually with larger crews and capaci- 

 ties greater than 3,000 liters per baitwell, 

 range from 41 to 70 gross metric tons. 



Standardization of Catch Per Effort 



Although both classes of vessels fish in the 

 same statistical areas, catches of Class 1 ves- 

 sels are nearly always smaller than those of 

 Class 2. Usually, Class 1 vessels have fewer 

 men hooking and use less bait in fishing. Cal- 

 culating separate catch per effort for the two 

 size classes complicates the estimation of ap- 

 parent abundance; therefore, it is desirable to 

 standardize the effort unit to obtain a single in- 

 dex of apparent abundance. Effort is defined as 

 an effective trip, i.e., one on which skipjack 

 tuna were caught. It represents 1 day's fishing, 

 although infrequently trips lasting 2 or 3 days 

 are reported. I have standardized the trips by 

 usingClass2 vessels as the standard size class 

 and translating Class 1 trips into Class 2 or 

 standard trips by using efficiency factors. 



Efficiency factors are ratios of yearly catch 

 per effective trip of Class 1 vessels to that of 

 Class 2 vessels; for example, over the entire 

 inshore area in 1948, Class 1 vessels caught 

 1.63 metric tons per trip; Class 2 vessels 

 caught 2.20 metric tons. The inshore efficiency 

 factor, then, is 1.63/2.20 or 0.74. Offshore, the 

 efficiency factor was 2.57/4.00 or 0.64. The 

 mean efficiency factor (geometric mean of in- 

 shore and offshore factors) was 0.69; this value 



