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FISHERY BULLETIN: VOL 77, NO. 4 

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FIGURE 11.— Distribution of Sternoptyx diaphana and S. pseudodmphana (also from Baird 1971; Haruta and Kawaguchi 1976). 



vergence fauna in the Pacific have circum- 

 Southern Ocean distributions (Craddock and 

 Mead 19701. McGinnis (1974) has presented evi- 

 dence in support of counterclockwise circulation in 

 the Pacific subantarctic with observed endemism 

 in mesopelagic fishes resulting from zoogeograph- 

 ic isolation of that region. Sternoptyx pseudo- 

 diaphana from this area can be distinguished 

 from Atlantic forms and the evidence present- 

 ed here is not in conflict with the McGinnis 

 hypothesis. In the tropical eastern North Atlantic 

 S. pseudodiaphana extends as far north as lat. 20° 

 N, long. 21° W (where it exists in sympatry with 

 S. diaphana ) and it is not unlikely that it occurs in 

 the Gulf of Guinea (Figure 11). Although some 

 specimens have been taken in the Benguela Cur- 

 rent area, the general paucity of material at pre- 

 sent available from the South Atlantic precludes 

 judgment as to whether a link exists between the 

 North Atlantic and Subtropical Convergence 

 populations. A potentially disjimct distribution, in 

 a manner less extreme than is expressed by 

 Stomias boa boa (Gibbs 1969), is given some tenta- 

 tive support by the apparent differences observed 

 between postlarvae from the North Atlantic and 

 South Pacific. Thus it is possible that the North 

 Atlantic population of S. pseudodiaphana is a di- 

 verging form of the Subtropical Convergence 

 stock. Finally, mention should be made of the 



single specimen apparently caught near the 

 Philippines. There is no obvious mistake in the 

 station labelling for this individual (Challenger 

 Stn. 218). The species range extends considerably 

 northward in the Atlantic and future studies may 

 also confirm a more complex distribution pattern 

 in the Pacific than present data would indicate. 



The species oi Sternoptyx are the deepest dwell- 

 ing of the marine hatchetfishes and do not exhibit 

 marked diel vertical migration. There are few cap- 

 ture records from opening/closing nets but new 

 data are provided from recent comprehensive sur- 

 veys (0-2,000 m) at three locations, in the eastern 

 North Atlantic and Gulf of Mexico, where 

 discrete-depth trawls were taken (Hopkins and 

 Baird 1973; Badcock and Merrett 1976). Sternop- 

 tyx diaphana and S. pseudohscura occur sympatri- 

 cally at all three locations. Sternoptyx pseudodia- 

 phana was found only at the eastern Atlantic 

 stations where it was the least abundant species 

 at lat. 18° N but more common at lat. 11° N. Indi- 

 viduals of all species were taken over a broad 

 depth range (ca. 500-2,000 m) but were only abun- 

 dant over a much more restricted depth zone (Ta- 

 ble 5). Thus, S. diaphana and S. pseudobscura, 

 which have broad areas of sympatry, tend to have 

 distinctly separate zones of maximum abundance 

 while S. pseudodiaphana , at the limits of its dis- 

 tribution, is somewhat intermediate and overlaps 



816 



