FISHERY BULLETIN: VOL. 72, NO. 4 



140* IW 



Figure 5. — Locality records and nighttime abundance of Nematoscelis gracilis and N. megalops adults in the Indian Ocean: a - NE 

 Monsoon period. (Solid lines represent approximate boundaries of distribution of A^. gracilis "old form," broken lines represent those of 

 "new form," and wavy lines those of N. megalops. ) 



15°47'E, 5 June 1963). (See Figure 14b.) Three 

 adult males and one female belonging to the new 

 form were caught at this station, but no old form 

 was found. Probably these new forms were trans- 

 ported westward by the Agulhas Current (Figure 

 7a). 



Pacific Ocean 



Nematoscelis gracilis is recorded from the 

 equatorial zone of the Pacific (Brinton, 1962). 

 Populations of this species were also shown to 

 have been carried by the Kuroshio system to as far 

 as lat. 40°N, east of Japan. The numerical density 

 was found to be much higher in the east than in 

 the west. In the present survey based on mid- 



water trawls from the Pacific, a similar pattern of 

 distribution was observed (Figure 7a). The new 

 forms were also found to occur in the Pacific, but 

 only south of the Equator. There Reid (1965) rec- 

 ognized an eastward flow at about 400-800 m (on 

 the basis of acceleration potentials at 125 cl/ton 

 (lat. 2°-8°S) and 80 cVton (lat. 8° - 20°S) 8 T). How- 

 ever, in the eastern Pacific the same latitudes are 

 occupied by old forms where Reid (1965) and Love 

 (1972) reported a narrow tongue of low oxygen, as 

 low as 0.2-0.5 ml/1, extending westward. The con- 

 tour of oxygen concentration of 0.5 ml/1 extended 

 as far west as long. 130°W between the Equator 

 and lat. 10°S (at 160 cl/ton ft T surface, 150-200 m). 

 This may account for the fact that new forms do 

 not reach eastward to the coasts of Chile and Peru. 

 The association of old forms with oxygen-poor 



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