Distribution of Fishing Effort and Catches of Skipjack 



Tuna, Katsuwonus pelamis , in Hawaiian Waters, by 



Quarters of the Year, 1948-65 



By 



RICHARD N. UCHIDA, Fishery Biologist 



Bureau of Commercial Fisheries Biological Laboratory 

 Honolulu, Hawaii 96812 



ABSTRACT 



The temporal and spatial distribution of fishing effort and skipjack tuna 

 catches are described on the basis of detailed data on catch, location, and effort 

 obtained each year from all vessels that fish full time for skipjack tuna in Ha- 

 waiian waters. Summarized are the amount of "effective" fishing (defined as a 

 trip on which skipjack tuna were caught), the resulting catch, and catch per 

 standard effective trip in each statistical area and combinations of statistical 

 areas (regions). 



The fishing is highly seasonal. Usually the effort expended and the catch in 

 the first quarter were 15 and 9 percent, respectively, of their annual totals. 

 Fishing intensified in May and second quarter catches, produced by 32 percent 

 of the annual effort, accounted for 33 percent of the annual catch. A further in- 

 crease in effort to 36 percent of the annual total in the third quarter increased 

 catches sharply so that they constituted 46 percent of the annual take. As the 

 abundance of skipjack tuna declined in the fall, fishing also declined; fourth 

 quarter effort, which was reduced to 17 percent of the annual total, produced 

 only 12 percent of the annual catch. 



INTRODUCTION 



Hawaii's live-bait fishing vessels traverse 

 181,000 km.^ of water surrounding the islands 

 in their search for schools of skipjack tuna, 

 Katsuwonus pelamis . Total annual catch has 

 ranged from a low of 2,780 metric tons in 1957 

 to a high of 7,329 metric tons in 1965. Varia- 

 tions in the total catch are evident not only 

 among years but also among areas fished. A 

 recent study, for example, indicated that the 

 catch of skipjack tuna within 37 km. of the is- 

 lands represented from 63 to 90 percent of the 

 total catch (Uchida, 1967). 



This report summarizes the amount of fish- 

 ing effort expended and the resulting skipjack 

 tuna catches in each of several areas and in 

 certain combinations of them, by quarters of 

 the year, for 1948-65. No attempt is made to 



relate variations in the catch rate and total 

 catch to environmental and biological condi- 

 tions. The basic data, however, will be useful 

 to such studies, which are now underway. 



SOURCE OF MATERIAL 



All catches of skipjack tuna (aku) from Ha- 

 waiian waters are recorded by the fishermen 

 on Aku Catch Reports, which are distributed 

 and collected by the Hawaii Division of Fish 

 and Game. I used catch reports of only those 

 vessels that fished exclusively for skipjack 

 tuna. 



The reliability of the locations of catches re- 

 ported in the Aku Catch Reports has been ques- 

 tioned by Yamashita (1958), who described in 

 detail the method the fishermen use to report 

 their catches. It is essential to realize that 



