significantly above average and tended to 

 be below average in succeeding months and 

 years. Clearly this examination of the 

 data demonstrates the initial high availa- 

 bility of at least a portion of the yellow- 

 fin tuna population to the long-line gear 

 followed by a consistent reduction in such 

 availability. Figure 22 demonstrates the 

 progressive westward movement of the Jap- 

 anese fishery across the Indian Ocean in 

 the early 1950s. 



In the Lesser Sundas and Timor area 

 the yellowfin catch rate of 1952-53 to 1956 

 to 1957 was progressively 7.1, 3.6, 310, 3.3, 

 2.0 (Mimura 1958). In the Banda-Flores Sea, 

 beginning with the same winter season, the 

 yellowfin catch was U.0, 2.8, 2.5 and 2.6 

 (no data on hand for 1956-57) . There are 

 yet insufficient data for the Japanese 



+ 10 



+ 5 

 



♦ 5 

 



+ 5 

 



+ 5 

 



+ 10 

 + 5 







♦ 10 



♦ 5 







♦ 5 

 



- 5 



90'-W5° 



. tJJJL 



g0'-90' 



70'-g0' 



60'-70° 

 (6.76) 



50*- 60' 

 (g.30) 



40°-50' 

 (6.SI) 



1953 



'954 



1955 



1956 



Figure 22. — Catch rates of Indian Ocean 

 yellowfin shown as deviations from 

 the area mean. 



Atlantic fishery to show trends. We can 

 however, refer to a news article which 

 stated in part, (Commercial Fisheries Review, 

 February, 1959, page 61) , "when Japanese 

 boats began fishing there (Atlantic grounds) 

 in the spring of 1957, catches ran around 

 13 tons a day, but late in that year they 

 were down to 7-9 tons, and at present they 

 are only 5-7 tons." 



In general, the literature is replete 

 with indications of the drop in catch rate 

 in Japanese yellowfin longline fisheries. 

 Although the trends cited are not neces- 

 sarily indicative of every series of oper- 

 ations, the pattern of a drop in return per 

 unit of effort is common. 



The catch rate for bigeye has occa- 

 sionally been similar to that for yellowfin, 

 but in general it does not follow the 

 yellowfin pattern of decline from initial 

 high catch rates. The rather consistent 

 decline in yellowfin catch rates is not 

 true of albacore either. Ctsu in his 

 article entitled, "A survey of the American 

 and Japanese Albacore Tuna Fisheries in the 

 Pacific through Examination of Catch Sta- 

 tistics," comments briefly on the albacore 

 catch rate data. He said in part, "the 

 fact that their (Japanese) present landings 

 are triple those of prewar years attest to 

 this (increase of catch with increased 

 effort) . It is, of course, possible that 

 the catch has not kept pace with effort and 

 that there is a general leveling off of 

 catch relative to the rising effort. It is 

 not possible to determine this without 

 detailed data on effort but in the face of 

 the continued high level of production in 

 the last several years, it seems unlikely 

 that exploitation has seriously affected the 

 albacore stock." He says further, "their 

 two North Pacific (albacore) fisheries 

 appear to be quite stable". . .and "the pres- 

 ent status of the Samoa-based fisheries... 

 is encouraging as far as albacore catch is 

 concerned." 



SIZE OF FISH IN CATCH 



As stated, there is a general tend- 

 ency for the large, old fish in a virgin 

 fish population to be harvested rather rap- 

 idly because fishing mortality of such fish 

 often exceeds recruitment. This phenomenon 

 has occurred in the longline fisheries we 

 are considering. Mimura (1958) noted that 

 there was a decrease of large fish, the 



32 



