to 67.7 million in 1963, the catch of albacore had 

 decreased 14 percent, from 2.1 million fish to 1.8 

 million. For example, in the western South Pacific 

 between long. 150° E. and 180°, the catch rates 

 decreased from .3.1 albacore per 100 hooks in 1962 

 to 1.9 in 1963, and in the central South Pacific (be- 

 tween 180° and 130° W., corresponding to the fish- 

 ing grounds of the American Samoa-based vessels) 

 the decrease was from -1.6 to 3.1 albacore per 100 

 hooks. Unlike the relatively low catch rate of 3.1 

 reported by the Japanese for 1963, our data from 

 American Samoa-based vessels show an average of 

 4.9 albacore per 100 hooks for the year (fig. 9). 

 This ditFerence may possibly be attributable to a 

 greater decree of selectivity for albacore on the 

 part of the American Samoa-based vessels. The 

 decrease in 1963, pointed out by the Japanese, is, 

 however, paralleled liy a similar decrease in our 

 data on catch per trip beginning early in 1963. 



■- WEIGHT 

 — NUMBER 



JFMAMJJASONOJFMAMJJASONDJFMAMJJASOND 



I I I , 1 I . I 



1963 



1964 



1965 



FiouKE 9. — Catch of albacore per 100 hooks, in numbers 

 and in weight, by the American Samoa-based vessels, 

 1963-65. 



Table 1. — Japanese data on catch and effort for albacore in 

 the South Pacific Ocean, 1962 and 1963 



[This table is based on table 10, Japan Fisheries Agency, 1966] 



Fishing area 



Number of 

 hooks 



1962 1963 



Number of 

 albacore 



1962 



1963 



Catch per 

 100 hooks 



1962 1963 



Long. 150° E.-180° 

 Lat. 10°-30° S. 



Mil- Mil- Thou- 

 tions lions sands 

 27. 7 17. 9 846. 2 



Num- Num- 

 ber of ber of 

 fish' fish 

 333. 1 3. 1 1. 9 



Thou- 

 sands 



Catch per 100 hooks is an index of apparent 

 abundance in terms of numbers of fish, whereas 

 catch per trip is measured in terms of weight of 

 albacore taken. The decrease in the latter index 

 in 1963, 1964, and part of 1965 was caused in large 

 part by a decrease in the average size of albacore. 



Though fluctuating greatly, the catch in num- 

 bers per 100 hooks from 1963 to 1965 did not show 

 a marked downward trend. On the other hand, the 

 same data, converted into catch in weight per 100 

 hooks (by using the monthly mean weight of al- 

 bacore sampled from the fishei-y), showed a de- 

 creasing trend through 1965 (fig. 9). Several pos- 

 sible causes for the observed deci-ease in the size 

 of the fish are discussed later. 



RELATION BETWEEN CATCH AND EFFORT 



The relation between annual total landings of 

 albacore and total fishing effort (number of fish- 

 ing trips) shown in figure 10, though seemingly 

 linear, needs to be interjDreted with caution, be- 



150 200 250 300 350 

 NUMBER OF FISHING TRIPS 



400 450 500 



Figure 10. — Relation between annual total landings of 

 albacore and total fishing triixs of American Samoa- 

 based vessels, 1954-65. 



ALBACORE TAKEN IN LONGLINE FISHERY IN AMERICAN SAMOA 



53 



