tive method for taking most of the pelagic 

 species of tuna, with the exception of 

 skipjack, and is apparently the only prac- 

 tical method for taking these species in 

 tropical waters where the mixed layer is of 

 substantial thickness. 



Japan, has, by using the longline 

 method, expanded her fisheries throughout 

 the tropical oceans of the world. This 

 expansion also has been aided by establish- 

 ing shore bases in various countries and 

 by using motherships . 



The temperature structure of the 

 tropical oceans seems to be such that the 

 live-bait method is not generally useful 

 for yellowfin tuna except in those areas 

 where the warm surface layer is relatively 

 thin, 200 feet or less. This situation 

 seems to occur only along the eastern 

 borders of the Pacific and Atlantic oceans, 

 and it is in precisely these areas that 

 live-bait fisheries for yellowfin are 

 important. 



The longline seems to harvest rather 

 selectively the larger size fish, and it is 

 likely that these larger fish are substan- 

 tially less abundant in terras of weight and 

 especially in terms of numbers than are the 

 smaller fish composing the same populations. 

 This would imply that fishing techniques, 

 which could be utilized where the mixed 

 layer is relatively thick and would take 

 broader ranges of sizes than is true for 

 the longline, might permit harvesting of 

 substantially greater amounts than could be 

 obtained by the use of the longline method. 

 Modest quantities of skipjack are taken by 

 purse seines in the eastern borders of the 

 ocean, but here, as elsewhere, skipjack 

 catches are dependent upon the availability 

 of live bait. Bait fishes are characteris- 

 tically fishes of inshore areas, whereas 

 skipjack appear to be generally abundant 

 throughout the tropical ocean regions, 

 hency adequate bait supplies are not 

 usually available in areas where skipjack 

 are abundant. This explains the concen- 

 tration of skipjack fishing at the borders 

 of the ocean. 



It is of interest to observe that the 

 Japanese live-bait fisheries have not under- 

 gone any expansion during recent years. In 

 fact, the only expansion of major importance 

 in live-bait fishing would seem to be that 

 principally by the French along the west 

 coast of tropical Africa. 



The under utilization of some of the 

 stocks of skipjack can be judged by an 

 examination of the recent history of one 

 Japanese fishery for skipjack in the western 

 Pacific. In 1937 the Japanese took over 

 30,000 tons of skipjack from the mandated 

 islands fisheries. There is no significant 

 skipjack harvest from this area today 

 because they are not permitted to obtain bait 

 from the inshore waters of these islands. 



BIBLIOGRAPHY 



ALVERSON, F. G. AND B. M. SHIMADA 



1957. A study of the eastern Pacific 

 fishery for tuna baitfishes, witii par- 

 ticular reference to the anchoveta 

 ( Cetengraulis mysticetua ) . Bull. Inter- 

 Araer. Tropical Tuna Comm. 2(2) : 25-79. 



ANDERSON, A. W. , W. H. STOLTING, 

 AND ASSOCIATES 

 1952. Survey of the domestic tuna indus- 

 try. U. S. Fish and Wildlife Service, 

 Spec. Sci. Rept.— Fish. No. lOlj, I4.36 p. 



DIEUZEIDE, R. 



19l9. Tuna fishing with live bait (La 

 Peche du thon a l'appatvivant) . La 

 Peche maritime, 28(858) : U03. 



FOOD AND AGRICULTURAL ORGANIZATION 

 Yearbook of Fishery Statistics. 

 Production. Issued annually. 



IVERSEN, E. S. AND H. 0. YOSHIDA 



1957. Longline and troll fishing for 

 tuna in the central equatorial Pacific, 

 January 1955 to February 1956. U. S. 

 Fisn and Wildlife Service, Spec. Sci. 

 Rept.— Fish. No. 17U, 23 p. 



JAPAN, MINISTRY OF AGRICULTURE AND FORESTRY 

 Annual reports of catch statistics on 

 fishery and agriculture. 



JAPANESE FISHERIES 



1957. Japanese Fisheries: Their Develop- 

 ment and Present Status, Tokyo, pub- 

 lished by Asia Kyokai, 253 p. 



LA PECHE MARITIME 



1956 Les madragues de Tunisie (The tuna 

 traps of Tunisia) . La Peche maritime, 

 35(9U2): 385. 



MIMURA, K. 



1958. Study of the fishing condition of 

 the yellowfin in the Indian Ocean, espe- 

 cially on the annual differences of the 



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