BADCOCK and BAIRD SYSTEMATICS OF STERNOPTYX 



and apparently excluded only from polar seas and 

 the Mediterranean ( Jespersen 1915; Geistdoerfer 

 et al. 1970; Baird 1971; Haruta and Kawaguchi 

 1976; Borodulina 1978). The geographic distribu- 

 tions of the species are presented in Figures 10 and 

 1 1 and, when coupled with the recent Russian data 

 (Borodulina 1978), exhibit certain distinct pat- 

 terns. The species tend to be limited to areas with 

 hydrographically similar characteristics (sensu 

 Baird 1971) and often exhibit mutually exclusive 

 distributions. The horizontal distributions con- 

 form in general to zoogeographically distinct re- 

 gions in the oceans (e.g., Baird 1971; McGowan 

 1977; Backus and Craddock 1977), the nature and 

 limits of which are only generally defined. From 

 the limited number of observations of vertical dis- 

 tribution in areas of sympatry, species which 

 share the water column tend to have separate 

 depths of maximum abundance. 



Sternoptyx obscura is confined to the Indo- 

 Pacific. In the eastern Pacific and Indian equato- 

 rial regions, it is the sole representative of the 

 genus. In the periphery of its distribution, it can be 

 relatively abundant (e.g., basins off southern 

 California) and can occur in sympatry with S. 

 diaphana and S . pseudobscura (Figures 10, 11). In 

 general the geographic distribution resembles 

 that of a number of other species, e.g., Myctophum 

 aurolanternatum, Cyclothone acclinidens. 



Scopelarchoides signifer, Rosenblattichthys alatus 

 (Nafpaktitis and Nafpaktitis 1969; Parin et al. 

 1973; Johnson 1974; Mukhacheva 1974; Quero 

 1974; Becker and Borodulina 1976), that are ap- 

 parent equatorial Indo-Pacific endemics. 



Sternoptyx diaphana and S. pseudobscura occur 

 in the Atlantic and Indo-Pacific and overlap for 

 much of their ranges (Figures 10, 11). Sternoptyx 

 pseudobscura, however, is apparently uncommon 

 in the western North Atlantic and the Caribbean, 

 where S. diaphana is abundant, yet it is well rep- 

 resented in the Gulf of Mexico. The occurrence of 

 all three species in Indonesian basin regions is 

 indicative of the zoogeographic complexity of the 

 mesopelagic ichthyofauna of that area. 



Sternoptyx pseudodiaphana is widely distribut- 

 ed in the Southern Ocean (see also Borodulina 

 1978) and associated boundary currents in the 

 Southern Hemisphere (Figure 11). Evidence from 

 other studies (e.g., Alvarino 1965; Gibbs 1968; 

 Krefft and Parin 1972; Nafpaktitis 1973; Mayer 

 1975; Bertelsen et al. 1976) has indicated that the 

 subtropical convergence area, at least in the South 

 Pacific, is a distinct zoogeographic region with a 

 number of endemic or characteristic species. The 

 occurrence of S. pseudodiaphana off South Aus- 

 tralia, in the Indian Ocean, and across the South 

 Atlantic between lat. 32°-40° S reinforces the con- 

 cept that many elements of the subtropical con- 



60^ 



'C) 



— I — 

 60* 



— r 



9cr 



■60° 



■40° 



20° 



20° 



•40° 



— 1 



90* 



—I — 

 60* 



— I 



30* 



— t— 

 0° 



— I — 

 30° 



120° 150° 180* ISO* 120* 



Figure 10. — Distribution of Sternoptyx obscura and S, pseudobscura (also from Baird 1971; Haruta and Kawaguchi 1976). 



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