Table 2. — Catch rates and fishing effort of American 

 Samoa-based vessels ' by vessel size groups, W63 and 

 1964 



Vessel size (tons) 



Item  



<80 81-100 101-120 121-140 >141 



Catch of albacore per 100 hooks: 



1963 4.6 4.9 5.1 5.8 5.1 



1964 4.9 4.7 4.8 5.4 4.4 



Number of flshmg trips: 



1963 68 266 44 24 21 



1964.- 23 171 59 27 36 



Percentage of fishing trips: 



1963 16.1 62.9 10.4 5.7 5.0 



1964 7.3 54.1 18.7 8.5 11.4 



1 Vessel-size data were not available for all vessels. 



The higher average catch rates achieved by the 

 larger vessels (121-140 gross tons) in 1963 and 

 1964, were probably due to the skill of the fishing 

 master in selecting productive fishing groiuids, or 

 to subtle differences in fisliing techniques rather 

 than to vessel size alone. For example, the high 

 average catch rate of 5.8 albacore per 100 hooks 

 in 1963 was achieved by only six vessels, which 

 rather consistently made good catches. One large 

 vessel fished 2 months in 1963 with poorer than 

 average results, but this vessel apparently left 

 the American Samoa fishery soon thereafter. 



Furthermore, the excellent performance of some 

 of the smaller vessels also argues strongly against 

 dependence of catch rates upon vessel size. A 60- 

 ton vessel, for example, attained higher than aver- 

 age catch rates in 6 of the 9 months during 1963 ; 

 its annual mean catch rate was 5.3 albacore per 100 

 hooks as compared with the average of 4.6 

 achieved by all vessels .smaller than 80 gross tons. 



It is, therefore, reasonable to conclude that 

 catch rates (catch per 100 hooks) are not influ- 

 enced by vessel size, and that they are valid indices 

 of the apparent abundanc* of albacore. 



Although catch per day's fishing and catch per 

 trip tend to increase with size of vessel, the fact 

 tliat relatively few vessels in the fleet were larger 

 than 120 tons or smaller than 80 tons enabled 

 us to use average catch per trip as a gross index of 

 apparent abundance for years in which data on 

 catch per 100 hooks are not available. Fortunately, 

 a very large proportion of the vessels in tlie Amer- 

 ican Samoa fleet has been tliose of about 100 tons 

 during the period of this study. 



SEASONA". AND GEOGr.APHIC ^ ATIIATIONS IN 

 CATCH PER 100 HOOKS 



The Nankai Regional Fisheries Research 

 Laboratory (1959) has published charts of the 

 average monthly albacore catch rate in each 1- 

 degree square area fished in the Pacific and In- 

 dian Oceans by using all data available through 

 March 1956. These charts are widely used today 

 as representative of catch rates under average con- 

 ditions. Koto (1966) published the average year's 

 catch rates of albacore in the Soutli Pacific Ocean 

 l)y sunmiarizing data obtained from the Japanese 

 tuna longline fishery between January 1950 and 

 December 1961. Many of the data from the Amer- 

 ican Samoa-based fishery are missing from both 

 the above publications. For this reason and to 

 make possible examination of the data for any 

 time trends in catch per unit of effort, more recent 

 data collected from the Ajnerican Samoa-based 

 vessels are presented in figures 12-14. The catch 

 rates (catch of albacore per 100 hooks) have been 

 averaged by quarterly periods for 1963, 1964, and 

 1965 and plotted by 2-degree square areas. 



These charts depict the shifting of the fishing 

 grounds during the year. The vessels from Samoa 

 tend to fish north of lat. 20° S. during the firet and 

 second quarters, although a few vessels venture 

 farther south to about lat. 28° S. Vessels tend to 

 scatter widely Iwginning about June or July, and 

 many boats fish between lat. 25° and 30° S. The 

 southern grounds are heavily fished during the lat- 

 ter part of the year. In general, the fisliing 

 grounds are in the north during the first half of 

 the year, and both north and south during the sec- 

 ond half. This situation probably holds true in 

 most years and may reflect the movements of alba- 

 core in the Soutli Pacific Ocean. Interviews with 

 fishermen indicate that catch rates in northern 

 waters are more favorable during the early months 

 of the year. Suzuki (1961), in recoixling his ob- 

 servations on the Samoa fishing operations in 1956, 

 attributed the seasonal shifts in fishing grounds to 

 movements of fish. He obsen'ed that most of the 

 vessels fished in the vicinity of lat. 27° S. in 

 August and September and then followed the 

 northward movement of the fish. 



Seasonal and geographical differences in catch 

 rates are not readily evident from these charts. 

 High catch rates (more than five albacore per 100 



ALBACORE TAKEN IX LOXGLIXE FISHERY IX AMERICAN SAMOA 



55 



