BEARDSLEY; POPULATION DYNAMICS OF ATLANTIC ALBACORE 



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Figure 9. — Total longline effort and catch per unit of 

 effort (CPUE) for the five major albacore fishing areas 

 in the Atlantic Ocean, 1956-68. 



NORTH ATLANTIC 



The North Atlantic supports two different al- 

 bacore fisheries, the longline fishery and the Bay 

 of Biscay surface fishery, while the South Atlan- 

 tic has only the longline fisheiy. The Bay of Bis- 

 cay fishery, conducted primarily by the French 

 and Spanish, has yielded about 45,000 metric 

 tons annually since 1963. The fishery catches 

 primarily 3- and 4-year-old albacore before they 

 are fully recruited into the longline fishery. 



There is evidence that albacore stocks in the 

 North and South Atlantic are separate ( Beards- 

 ley, 1969; Koto, 1969; Yang, Nose, and Hiyama, 

 1969) . Koto indicates, however, that there may 

 be some mixing of immature albacore between 

 the South Atlantic and Indian Oceans. I com- 

 bined catch and effort data from the two major 

 albacore fishing areas in the North Atlantic and 



from the three areas in the South Atlantic and 

 treated each group as separate stocks. 



From 1957 through 1965 I used only Japanese 

 data (Shiohama, Myojin, and Sakamoto, 1965; 

 Fisheries Agency of Japan, 1966, 1967a, 1967b) 

 since the longline fishery during those years was 

 almost exclusively Japanese. For 1966, 1967, 

 and 1968 I used Japanese data (Fisheries Agen- 

 cy of Japan, 1968, 1969, 1970) as well as esti- 

 mated Chinese and Korean catch data (Wise, 

 1970) . Catch per unit of eflfort (CPUE) in this 

 discussion is the number of albacore caught per 

 hundred hooks fished. CPUE was calculated by 

 summing the number of albacore caught in a 

 given ai'ea in a given year, multiplying by 100, 

 and dividing by the number of hooks fished in 

 that area during the year. Only the catch data 

 were available from the Chinese and Korean 

 fishery. Total Chinese and Korean fishing effort 

 for 1966, 1967, and 1968 was obtained by using 

 Chinese and Korean albacore landings and Jap- 

 anese CPUE and back calculating to the number 

 of hooks fished. This procedure assumes that 

 CPUE for the Chinese and Korean fleets was the 

 same as for the Japanese fleet. This is probably 

 not true; however, the difference is not likely 

 to be large. The Chinese and Korean fishing 

 effort in the Atlantic was not great until 1968 

 and by then their fishing efficiency was probably 

 comparable to that of the Japanese. 



One of the more common mathematical models 

 used to express yield from a stock of fish is the 

 equilibrium-yield model used by Graham (1935) , 

 Schaefer (19-54, 1957), and others. One of the 

 major advantages of this ty]5e of model is that 

 it requires only catch and effort data. Assuming 

 a fishery that has attained equilibrium condi- 

 tions, a plot of CPUE against effort should show 

 a linear decline which will produce a parabolic 

 curve of yield when plotted against effort. Fox 

 (1970) has argued that the relationship between 

 CPUE and effort is more nearly exponential than 

 linear. Both models, however, predict almost 

 identical yields for the ascending limb of the 

 yield curve. The major difference in the two 

 models occurs after theoretical maximum yields 

 have been exceeded. I chose to limit my analysis 

 to the linear model. The Atlantic longline fish- 

 ery, however, has never been under equilibrium 



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