the data presented are the number of hooks 

 set and the catch in numbers of 10 species or 

 groups of species for each 5° x 5° square 

 and each month. The data for 1969 became 

 available as this report was in preparation 

 (Fisheries Agency of Japan, 1971) and are 

 summarized in Table 1 but not included in 

 this analysis. 



From 1956 through 1966 the values pub- 

 lished are from the longliners from which 

 logbooks were available. Conversion factors 

 are provided to adjust these data to estimates 

 for the whole Japanese fleet. The data from 

 1967 onward were adjusted before publica- 

 tion. The factors used to adjust the data to 

 values for the whole Atlantic fleet are: 



1956 



1.00 



1957 



1.15 



1958 



2.57 



1959 



1.97 



1960 



1.34 



1961 



1.29 



1962 



1.72 



1963 



1.60 



1964 



1.52 





1.47 



1965 



1.60 





1.27 



1966 



1.54 





1.17 



1967 



1.21 





1.14 



1968 



1.61 





1.16 



(Longliners) 



(Motherships with longline boats) 



(Longliners) 



(Motherships with longline boats) 



(Longliners) 



(Motherships with longline boats) 



(Longliners) 



(Motherships with longline boats) 



(Longliners) 



(Motherships with longline boats) 



Factors for 1961 and 1962 have been changed 

 slightly from those indicated in Shiohama 

 et al. (1965) because of the deletion of some 

 suspect data on the advice of Dr. Akira Suda 

 of the Far Seas Fisheries Research Labora- 

 tory of the Fisheries Agency of Japan. Shio- 

 hama (1971) has recently published a table 

 of corrections which agrees almost exactly 

 with Suda's letter — our data are very slightly 

 at variance with the later corrections. 



Table 1 summarizes the Japanese Atlantic 

 catch and fishing effort for the period studied. 



Through 1965 the Japanese fleet accounted 

 for 90% or more of all Atlantic longline catches. 

 The percentage decreased rapidly in 1966 

 and following years as the Japanese reduced 

 their effort and the Chinese (Taiwan) and 

 South Koreans increased theirs. In 1969 the 

 Japanese fleet only took about 30% of the 



total Atlantic longline catch, but fishing oper- 

 ations were widely enough distributed in time 

 and space that the Japanese fleet could still 

 be considered a good sampling device for de- 

 riving indices of catch per unit of effort and 

 abundance. 



The tunas and billfishes were originally 

 identified in the data reports only by their 

 Japanese and English common names. Be- 

 ginning in 1967 the names for the Atlantic 

 tunas and billfishes are given as follows: 



Japanese name Scientific name 



Kuromaguro 



Minamimaguro 



Binnaga 



Mebachi 



Kihada 



Mekajiki 



Nishimakajiki 



Nishikurokajiki 



Shirokajiki 



Nishibashokajiki 



Kuchinagufurai 



Katsuo 



Thunnus thynnus 

 T. maccoyii 

 T. alahinga 

 T. obesns 

 T. albacares 

 Xiphias gladius 

 Tetraptums albidus 

 Makaira nigricans 

 M. indica 



Istiophorus albicans 

 Tetrapturus pflnegeri 

 Euthynnus pelamis 



METHODS 



English name 



Bluefin tuna 

 Southern bluefin 

 Albacore 

 Bigeye tuna 

 Yellowfin tuna 

 Swordfish 

 White marlin 

 Blue marlin 

 Black marlin 

 Sailfish 



Longbill spearfish 

 Skipjack tuna 



The area covered in this study is the At- 

 lantic Ocean, exclusive of the Mediterranean 

 Sea, but including the Gulf of Mexico and 

 Caribbean Sea, from lat 45 °N to 40 °S, west 

 of long 20 °E. Twelve of the 6,045 observa- 

 tions in 1956-68, including some 72,000 hooks 

 in 1965-68, occurred just north or south of 

 this area and are not included in subsequent 

 consideration. Two hundred fifty 5° X 5° 

 squares all or part water are included. Two 

 hundred thirty of these were fished at least 

 once during the 13-year period. The 20 squares 

 in which there was no fishing are in coastal 

 areas or at the southern boundary. 



The number of month-squares for which 

 there are observations in a given year varies 

 from 23 in 1956 to 1,053 in 1965. An average 

 year has about 464 of a possible 2,760 (230 

 x 12) month-squares. When the data are 

 grouped into quarters of the year, the range 

 is from 19 quarter-squares in 1956 to 548 

 quarter-squares in 1965, with an average of 

 about 264 of a possible 920 (230 X 4) quarter- 

 squares. Since the mean density is 29% (264/ 

 920) for quarter-squares vs. 17% (464/2,760) 



