282 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



I wish to thank the staff of the Hawaii Division 

 of Fish and Game who collected the fish-catcli re- 

 ports that form the basis of this study. Vernon E. 

 Brock and Tamotsu Shimizu made their data 

 available for study. Additional information was 

 received from Saul Price of the U.S. Weather -Bu- 

 reau who furnished the data on small craft warn- 

 ings. Peter Wilson of Hawaiian Tuna Packei's, 

 Ltd., was instrumental in obtaining the logbooks 

 from two fishing sampans; and Dr. Robert Riff en- 

 burgh suggested certain useful statistical 

 procedures. 



UTILIZATION OF DATA 



The fish-catch reports (fig. 2), completed by the 

 fishermen, were used in this study. Ite^is in these 

 reports are treated as follows : 



Thme of catch. — The interval from the begin- 

 ning of 1952 througli 1953 was divided into bi- 

 weekly periods (table 1). Catch reports were 

 grouped by periods according to date of landing. 



Area of catch. — -The catch reports were sorted 

 and reported according to statistical area (fig. 3). 

 For reasons discussed under Sources of Error, the 

 statistical areas have been summarized in terms of 

 zones and regions (fig. 4) . 



Pounds caught. — This figure was used exactly 

 as recorded in the catch reports. 



Average size of skipjack caught. — The total 

 weight was divided by the estimated number 

 caught to arrive at the average weight per fish in 

 the catch. Catches were then classified according 



to the following categories: (1) small fish (aver- 

 age weight 10 pounds or less) , (2) large fish (aver- 

 age weight greater than 10 pounds) , or (3) catches 

 for which no size estimate was possible, because 

 the number of fish caught was omitted from the 

 report. 



Estirnate of total number of skipjack caught in 

 each size group. — A simple proportion, utilizing 

 the known weights and numbers, was used to esti- 

 mate the numbers of small and large skipjack in 

 the total catch. For example, if the summary of 

 data from the fish-catch reports for a particular 

 region and period yields the following informa- 

 tion : 



• Unlmown. 



then, the estimated total number of small skipjack 



e,,gHt IS ^^«^lg») =9,000, and the esti- 

 oO,000 



mated total number of large skipjack caught is 



(2,500) -(120,000) 



80,000 



= 3,750. 



Unusable f.^h-catch reports. — A small number 

 of reports was set aside and not used, except to 

 accumulate gross totals of pounds caught. If a 

 report fell into one or more of the following cate- 

 gories, it was classified as unusable: (a.) no sta- 

 tistical area was given on catch report, or area 

 number given did not appear on Division of Fish 

 and Game Chart (fig. 3) ; (6) several statistical 

 area numbers were given so that assignment of the 

 catch to any single zone or region was impossible ; 

 (c) several trips were apparently grouped on one 

 catch report so that estimates of fishing effort 

 would be erroneous. 



All other reports were considered usable. 



CHOICE OF UNIT OF FISHING EFFORT 



The fish-catch report gives no direct informa- 

 tion on the amount of effort. There are no data to 

 indicate the number of fishermen making the 

 catch, the time in terms of scouting and fishing, the 

 number of mireported trips with no catcli, or any 

 of the other factors which might be pertinent. 

 The fish-catch reports provide, insofar as the de- 

 termination of effort is concerned, a listing of 



