(t = -11.31; df = 10; p <0.001). We can 

 conclude, therefore, that the amount of bait 

 used in fishing contributed to the larger catch 

 per effective trip among Class 2 vessels. 



STANDARDIZATION OF CATCH PER 

 EFFECTIVE TRIP 



Differences between the large and the small 

 vessels in numbers of men and in quantity of 

 bait and hence in catching ability can compli- 

 cate the estimation of apparent abundance. 

 Rather than analyze data for the two classes 

 of vessels separately, I have employed only one 

 index, based on a "standard" unit of fishing 

 effort. This unit is derived from a set of con- 

 version factors which translate unequal fishing 

 practices and capacities into a standard unit. 

 For example, under conditions of equal 

 abundance, when a small vessel makes a 

 smaller catch than a large vessel, standardi- 

 zation of the effort units takes into account 

 the differences in their fishing power. A gen- 

 eral discussion of the problems in standardiz- 

 ing fishing effort may be found in Gulland 

 (1955, 1956), in Shimada and Schaefer (1956), 

 and in Schaefer (1963). 



Efficiency Factors 



The yearly Y/g of the two classes of vessels 

 by areas permits the calculation of efficiency 

 factors (Shimada and Schaefer, 1956). For 

 each area the ratio of the yearly Y/g of Class 1 

 to that of Class 2 was computed. For example, 

 from table 9, values of Y/g for 1952 were as 

 follows: 



Class 1: Inshore —3,586 pounds /effective trip 

 Offshore — 3,728 pounds/effective trip 



Class 2: Inshore —4,323 pounds/effective trip 

 Offshore — 5,722 pounds/effective trip 



For Class 1 vessels, the efficiency factor for 

 inshore was 3,586/4,323 = 0.83; for off"shore, 

 it was 3,728/5,722 = 0.65. The efliciency fac- 

 tors for Class 2 vessels are fixed at 1.00 for all 

 years. The mean efficiency factor for the year 

 is the geometric mean of the inshore and off-- 

 shore values. The geometric mean is appropri- 

 ate for averaging ratios. 



The mean efficiency factors for Class 1 ves- 

 sels and the average for the 11-year period 

 not only demonstrate the greater capability of 

 Class 2 vessels, but also the variability of the 



192 



factor (table 11). For example, if the Y/g of 

 Cla.ss 1 vessels were some constant proportion 

 of that for Class 2 vessels, one would expect an 

 almost constant eflJiciency factor. The efficiency 

 factors of Class 1 vessels, however, were as 



Tabi.k 11.— Tn/we.s of efficiency factors for Class 1 Hawaiian 

 skipjack tuna vessels in terms of a fixed value of 1.00 for Class 

 2 vessels 



[These factors were iLsed to standardize the unit of effort in 1952-62] 



high as 0.86 and as low as 0.68. These values 

 show no trend, and apparently are not related 

 to good and poor years. 



The efficiency factors by area (computed in 

 terms of a fixed value of 1.00 for Class 2 ves- 

 sels, off-shore) for each vessel class (table 12) 

 show that the values for both Class 1 and 

 Class 2 were almost consistently smaller for 



T.^Bi.E 12.— Va/i/ra of efficiency factors for Class 1 Hawaiian 

 skipjack tuna vessels inshore ami offshore and for Class 2 

 vessels inshore in terms of a fixed value of I.OO'for Class 3 

 vessels offshore 



inshore than for offshore fishing. The average 

 for the 11-year period indicates that the off"- 

 shore values of efficiency factors are higher 

 than their respective inshore values. Further- 

 more, the mean efficiency factor for Class 1 

 offshore is slightly larger than that for Class 2 

 inshore. This result was not unexpected be- 

 cause efficiency factors do not take into ac- 

 count the ability of a vessel to visit distant 

 areas where fish density may be higher. Al- 



SKIP.IACK IN HAWAIIAN WATERS 



