

PERCENTAGE OF OCCURRENCE 

 20 40 60 80 100 % 





i i i i i i i i i i 



s 





V/////////////////////A 





Ck 



1 



f D : 43 \ 

 \N: *2J 



3D 



y// .. y /M 











1 1 DAY V///A 



NIGHT 



Figure 2. — Vertical distribution of swordfish larvae as 

 seen from catches in surface (S) and subsurface (Sb) 

 larva-net tows. The numbers of day (D) and night (N) 

 stations at which larvae were caught are shown in 

 parentheses. 



The difference between the surface and subsurface 

 catches was quite marked during the day but not as 

 much during the night. This difference probably 

 represents diurnal vertical movements among larval 

 swordfish. 



GEOGRAPHICAL DISTRIBUTION 



The occurrence of larvae was plotted by unit 

 areas of 1° squares (Fig. 3). Also included in the 



same figure are the areas of relatively high catch 

 rates for adult swordfish. The adult catch rates 

 were based on 1970 data from the Japanese longline 

 fishery, and included unit areas of 5° squares where 

 the annual average catches exceeded 1.0 fish per 

 1000 hooks fished. (All unit areas where the total 

 fishing effort consisted of less than 20,000 hooks 

 were excluded.) 



The distribution of the larvae is seen to be con- 

 tinuous in tropical and subtropical waters extending 

 from the central Indian Ocean clear across to the 

 eastern Pacific Ocean in the vicinity of long. 120°W. 

 The apparent absence of larvae in the South China 

 Sea and in the western Indian Ocean is probably 

 attributable to lack of sufficient sampling effort in 

 those waters since Taning (1955) and Gorbunova 

 (1969) have shown the presence of larvae in these 

 areas. 



The northernmost record of larval occurrence in 

 the western Pacific was at lat. 31°N, long. 132°E, in 

 the vicinity of Kyushu. In the central Pacific it was 

 at lat. 25°N, long. 158°W, just to the north of the 

 Hawaiian Islands, and in the eastern Pacific, at lat. 

 9°N, long. 120°W. The southernmost occurrence in 

 the southwestern Pacific was at lat. 22 C S, long. 

 170°E, and in the southeastern Pacific at lat. 

 22°38'S, long. 105°24'W. Although no larvae were 

 caught in waters south of lat. 10°S in the central 



Figure 3. — Distribution of swordfish larvae (dots) and adults (hatched) in the Pacific and Indian Oceans. The adult 

 distribution is represented by areas in which longline catches averaged greater than 1.0 fish per 1000 hooks during 1970. 

 and where fishing effort exceeded 20.000 hooks fished. 



262 



