30" 



130° 



120° 



FISHERY BULLETIN: VOL. 78, NO, 3 



80° 70° 



20" 



10° 



10° 



20° 



•5 



•3 



•3 



•19 



•I 



•II 



•18 



•20 



•7 



•7 

 •2 

 •7 

 7^^9- 



•6.6 



2«| 



•6 



I.I 

 2 



) 



•4 



•1.4 



•2 



it'^ 



10. 



• •i-7«^ie 



Halobates sericeus 



130° 



120° 110° 100° 90° 



Figure 6. — Halobates sericeus distribution, as in Figure 3, 



80° 



70° 



ure 6). It occurs completely outside the range of//. 

 sobrinus (Figures 4, 5) and shows only very small 

 overlap with//, micans (Figures 3, 5). 



Halobates splendens , rarest of the four EAS- 

 TROPAC species, has not been found north of 

 about lat. 8° N (Figure 7 ). The captures reported in 

 the Chile Current (Figure 2) indicate that this 

 species may be primarily associated with the cen- 

 tral South Pacific watermass or the South Amer- 

 ican coastal current System. Sampling in this 

 region is insufficient at present to permit better 

 definition of its range. 



The distributions oi Halobates spp. appear to be 



controlled by two major influences: 1) the patterns 

 agree with broad, general surface-circulation pat- 

 terns, and 2) species' regions of high abundance 

 generally tend not to overlap. We do not know 

 whether the nonoverlap is due to competitive ef- 

 fects or to physiological adaptations by each 

 species to a particular environmental regime. 



Abundance 



Two important difficulties in deriving quantita- 

 tive estimates of Halobates spp. abundance are: 1) 

 most neuston nets (including ours) tend to skip out 



586 



