INTRODUCTION 



Since the early 1900's when the fishery for 

 skipjack tuna, Katsuwonus pelamis , or aku, as 

 it is locally called, began, the Hawaiian skip- 

 jack tuna fishermen have been modifying their 

 vessels to increase their fishing power. They 

 replaced scull or sail power with engines to 

 increase the vessels' operating range, added a 

 flying bridge to extend the vessels' scouting 

 range, redesigned the hulls to improve the ves- 

 sels' speed, stability, and maneuverability in 

 rough channel waters around the islands, and 

 increased the carrying capacities of the ves- 

 sels' fuel tanks, ice holds, and baitwells. 



The NMFS (National Marine Fisheries Ser- 

 vice) (formerly the Bureau of Commercial 

 Fisheries) in Honolulu also has attempted to 

 improve fishing efficiency in the skipjack tuna 

 fishery. Realizing that fishing with pole and 

 line was often seriously hampered by a short- 

 age of live bait, the NMFS tried purse seines 

 (Murphy and Niska, 1953) and gill nets (Matsu- 

 moto, 1952; Shomura, 1963), but these attempts 

 were unsuccessful in catching commercial 

 quantities of skipjack tuna. 



Until new means of catching skipjack tuna 

 can be found, the Hawaiian tuna fishermen must 

 rely on pole and line and live bait; therefore, 

 the NMFS decided to try to improve the pole- 

 and-line operation. This study of the operations 

 of the fishery provides some basic information 

 which is necessary for suggesting improve- 

 ments. In addition, the information is poten- 

 tially useful for obtaining the best possible 

 index of abundance of the fish for biological 

 studies. 



SOURCE OF DATA 



The captains and crewmembers of seven ves- 

 sels participated in this study. NMFS techni- 

 cians, who were permitted to remain aboard 

 the vessels for 5-6 days a week, collected data 

 on baiting, fishing, and supporting activities 

 from June through August 1967. 



When baiting, the technicians reported on the 

 species and quantity caught, the mortality in- 

 curred in transporting the bait from catch site 

 to the vessel, and the time required for the 

 entire operation. 



On fishing trips, the technicians recorded the 

 time of departure and return and the start and 

 end of scouting. For each school, they recorded 

 the time of sighting, the start of chumming, and 



the start and end of fishing. They estimated 

 the amount of bait used per school, noted the 

 number of men that fished, counted the number 

 of fish caught, and obtained the average weight 

 of the fish in the school from a sample con- 

 sisting of 10 fish selected at random. While 

 pursuing the schools they estimated the amount 

 of sky covered by clouds, the height of the 

 waves, the number of birds in the flock, and 

 identified the predominant birds associated with 

 the school. After fishing and at 2-hour inter- 

 vals while scouting, the technicians checked 

 surface water temperatures and collected water 

 samples for salinity determination. When pos- 

 sible, the technicians also approximated the 

 positions of schools sighted and of schools 

 fished by taking compass bearings from the 

 vessel to recognizable landmarks. When land- 

 marks were not visible, the captain estimated 

 the position after considering the ship's course 

 and approximate distance or hours from land. 



In port, the technicians recorded time and 

 number of men required to unload the catch and 

 to load ice. 



ANALYTICAL PROCEDURES 



We summarized data on baiting, fishing, and 

 supporting activities first by vessel, then col- 

 lectively for all vessels over the 3 months. In 

 examining the relation between any two vari- 

 ables, however, we separated the data into 

 appropriate units, within which we summarized 

 all other information important to our analysis. 

 For example, in examining catch in relation to 

 the number of men fishing, we separated the 

 schools by number of men fishing; then, for 

 each group (1, 2, 3,, ..10 men fishing) we sum- 

 marized the catch per school and other infor- 

 mation such as the amount of bait used and 

 fishing duration. 



We used data from incomplete logs in some 

 of our analysis, but only after we established 

 that the data would not bias the results. For 

 example, on one vessel, a newly hired techni- 

 cian failed to record data on all schools sighted 

 and chummed: therefore, his data were used 

 only in summaries dealing with catch and not 

 in summaries of schools sighted and chummed. 

 The result was that although we could use the 

 catch data from 244 trips, we were able to use 

 the data on schools sightings from only 231 

 trips. 



Catches of species other than skipjack tuna 

 were infrequent (only about 0.8 percent, by 



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