of fishing effort and by weather and sea con- 

 ditions. Catch per unit of effort calculated in 

 terms of uncorrected fishing effort is also un- 

 reliable because it varies from year to year 

 with changes in the fishing fleet. The fleet is 

 made up of vessels of different sizes, and num- 

 bers of these change as some enter and some 

 leave the fishery. Both size and number affect 

 the catch per unit of eft'ort. An important phase 

 of this study is the derivation of a measure of 

 abundance of skipjack in Hawaiian waters 

 based on catch per unit of effort in standard- 

 ized units that are unaffected by changes 

 in the fishing fleet. 



SOURCES OF MATERIALS 



The basic data for this study were obtained 

 from Fish Catch Reports (January 1952 to 

 June 1954) and Aku Catch Reports (July 1954 

 to December 1962) submitted by the fishermen 

 to the Hawaii Division of Fish and Game. 

 Catch reports of only those vessels that fished 

 for skipjack tuna full time were u.sed. The 

 report form has undergone several revisions 

 through the years, but all versions have carried 

 spaces for the following information: The date 

 of landing, the pounds of skipjack caught, and 

 the fishing area. Yamashita (1958) described 

 the method of reporting the areas fished by a 

 skipjack vessel. Briefly, a fisherman reports 

 only the code number corresponding to the 

 statistical area where the catch was made. 

 These areas are indicated on the Division of 

 Fish and Game's Fisheries Chart No. 2 (see 

 Yamashita, 1958: fig. 2). 



Data on number of men hooking per trip 

 were obtained from Aku Boat Interview Sheets 

 (January 1950 to July 1956), which were col- 

 lected and checked by the personnel of the 

 Division of Fish and Game, from logbook 

 records (1957-59), and from Sampan Interview 

 Records (August 1959 to June 1961). 



DESCRIPTION OF THE FISHERY 



The present brief de.scription of the fisher>' 

 and review of fishing operations is based on 

 June (1951). The number of skipjack tuna 



sampans fishing full time reached a maximum 

 of 28 in 1951, but since then has declined; in 

 1963 only 20 vessels were fishing full time for 

 skipjack. The vessels, generally of wooden con- 

 struction, range from 58.3 to 80.5 feet in regis- 

 tered length and from 27 to 77 in gross tonnage. 

 These vessels carry 6 to 14 men per fishing trip. 



The nehu or anchovy, Sfolcphorus purpiireus 

 Fowler, makes up about 92 percent of the bait 

 catch; a second bait is the iao or silverside, 

 Prnncsus insularum (Jordan and Evermann). 

 Each vessel catches its own bait, fishing day 

 pnd night until a sufficient supply is obtained. 

 All the vessels have si.x baitwells with screened 

 holes at the bottom through which sea water 

 circulates. 



The Hawaiian skipjack tuna fishermen usual- 

 ly confine their fishing and scouting operations 

 to waters within 90 miles of the main islands. 

 Skipjack on the fishing ground are indicated to 

 the fishermen almost exclusively by bird flocks 

 which are often associated with schools of 

 fish. When a school has been sighted the 

 captain attempts to intercept it. Once the head 

 of the school is reached, water sprays are 

 turned on and the "chummer" scatters live 

 bait into the water. If the skipjack bite, the 

 fishermen begin fishing off the stern. Fishing 

 continues until the bait supply is exhausted or 

 until the captain decides that further fishing 

 is not worthwhile. If chumming is unsuccess- 

 ful, the school is abandoned and scouting is re- 

 sumed. The sampans may encounter several 

 .skipjack tuna schools during the day, but the 

 fish may bite in only about half of them. 

 Scouting and fishing are discontinued as dark 

 approaches, and the ves.sels usually head for 

 port to unload the day's catch. 



TRENDS IN CATCHES OF SKIPJACK TUNA 



To show the trends in catches of skipjack 

 tuna from Hawaiian waters, catch statistics 

 were summarized by months and quarters for 

 each year and by two broad geographical areas. 

 Comments on the trends of catches are based 

 on tabulation of data for 1952-62; therefore, 

 the results may not be in complete agreement 

 with those published for 1948-53 by Yamashita 

 (1958). 



182 



SKIPJACK IN HAWAIIAN WATERS 



