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III. STATUS OF THE STOCKS 



III. A. Stock Structure 



The stock structure of the swordfish population of the Pacific 

 Ocean has not been clearly defined. Available data on distribution of 

 larvae and on longline catch rates suggest that the population consists of 

 either 1) a single, Pacific-wide stock, or 2) three separate stocks with 

 centers of concentration in the northwestern (Area 1), southwestern (Area 

 2), and eastern (Area 3) regions of the Pacific Ocean (Figure 1). 



III.B. Stock Assessment and Fishery Evaluation 



III.B.l. Trends in Catch-per-Unit-Effort 



The trends in swordfish catch rate and effort for the 

 Pacific Ocean are shown in Figures 4, 5, and 7. The longest available time 

 series of catch rates is for the Japanese longline fleet. Total Pacific 

 catch rates for this fleet reached a peak of about 10 fish/10,000 hooks in 

 1958, then declined to a low of 4 fish/10,000 hooks in 1967; rates have 

 since stabilized at about 5 fish/10,000 hooks. 



III.B. 2. Results of Production Model Analysis 



The condition of the swordfish stocks of the Pacific was 

 evaluated, based on different hypotheses about the stock structure of the 

 population: hypothesis 1 assumed a single Pacific-wide stock, and 

 hypothesis 2, three separate stocks. 



Single Pacific-wide Stock- -The relation of catch and 

 effective fishing effort (a projection of effort for catches where no 

 effort data are available), assuming a single Pacific-wide stock, is shown 

 in Figure 7. The data points fall into two clusters, separated by a sharp 

 break between 1963 and 1964, which corresponds approximately to the period 

 when the operational methods in the productive northwestern fishing area 

 changed from longline night fishing, which is directed at swordfish, to a 

 day operation which targets on tunas. 



The production model does not appear to fit the data 

 well, because the points offer no solution for the 1964-1975 data series 

 and give a maximum sustainable yield (MSY) estimte of 20,000 mt per year 

 with 2.2 million hooks/5° area for the 1952-1963 series. Presumably during 

 the 1952-1963 period the fishery was more efficient in catching swordfish 

 than during the 1964-1975 period. The current (average for 1966-75) catch 

 of about 14,100 mt produced by 1.8 million hooks/5° area) indicates that 

 the fishery does not appear to be overexploiting the stock and that the 

 stock is in good condition. 



