FISHERY BULLETIN: VOL. 78. NO. 3 



^ 



10 20 30 40 50 60 70 

 % of Samples Containing H. micans 



FIGURE 10. — Percentage of samples containing Ha/o6a?es mi- 

 cans and//, sohrinus compared by cruise series (Table 1). Series 

 numbers are shown beside each point. Note inverse relationship. 



CONCLUSIONS 



Four pelagic species of Halobates — H. micans, 

 H. sericeus, H. sobrinus, and//, splendens — are 

 found in the eastern tropical Pacific area. Within 

 the EASTROPAC area, the ranges of the four species 



agree well with dominant oceanic zones or do- 

 mains; e.g., tropical-equatorial, central water- 

 mass, and coastal upwelling. The worldwide dis- 

 tributions of the four species in the Pacific Ocean 

 have also been found to agree with recognized 

 oceanic domains (Herring 1961; Savilov 1967) al- 

 though at present data are still insufficient to 

 clearly define some boundaries, especially in the 

 southern tropical Pacific. Although species may 

 cooccur in the EASTROPAC area, geographical 

 regions of high abundance for H. micans, H. so- 

 brinus, and H. sericeus show little overlap. Our 

 estimates for maximum abundance (lower 

 bounds) for the two more abundant species, H. 

 micans andH. sobrinus, are 400-10, OOO/km^. This 

 is likely to be conservative because they can avoid 

 nets and because the neuston net used in our study 

 did not sample in an ideal manner. We found Halo- 

 bates to be most abundant in 24°-28° C waters. The 

 two abundant species showed very patchy dis- 

 tributions. Present temporal and spatial cov- 

 erages are insufficient to allow us to define possi- 

 ble seasonal variations in population density or 

 structure. 



It seems clear that the distributions of Halobates 

 spp., inhabiting a strictly two-dimensional world, 

 are governed by the same oceanic processes which 

 shape the distributions of other marine species 

 that inhabit a three-dimensional world. /^ 



A. Series 10 (March 1967) 



1-120 



oi 4— I 



Q. 



E 



co ^ 

 ~\ 



|2H 



I' 



oH- 



NO. SAMPLES 



16 



22 24 



TEMPERATURE °C 



FIGURE 11. — Number of Halobates 

 specimens (data for all four species 

 combined) per positive sample vs. sea- 

 surface temperatures. A. Series 10, 

 March 1967. B. Series 40, August 1967. 

 (Exact dates and area covered given in 

 Table 1 and Figure 1.) 



B Series 40 (August 1967) 



NO. SAMPLES 



MEAN NQ INDIVIDUALS/SAMPLE 



20 22 



TEMPERATURE °C 



590 



