198 U.S. NATIONAL MUSEUM BULLETIN 291 



16, The three-dimensional distribution of Bathyteuthis is governed 



in part by physicochemical characteristics, but the primary lim- 

 iting factor in the distribution of this bathypelagic species is a 

 biological phenomenon : organic productivity. High organic 

 production accounts for the abundance of specimens from the 

 Southern Ocean, Peru Current, Gulf of Panama, eastern 

 Atlantic, etc. 



17. The vertical range of B. abyssicola in the Antarctic Ocean is deter- 



mined to extend from 500 to 2500 m with a peak of abundance 

 between 1000 and 2250 m. 

 IS. Larvae and juveniles tend to live at shallower depths than adults. 

 The occurrence of adults in the shallower end of the range is 

 generally related to unusual oceanographic conditions, e.g., up- 

 welling along the Antarctic Divergence. 



19. B. abyssicola^ a true bathypelagic squid, lives at least 1000 m 



above the ocean floor. 



20. Although B. abyssicola occurs throughout the Antarctic Ocean 



it is not equally abundant in each region ; its relative abundance 

 is greatest in the Drake Passage Convergence, the southern 

 Peru Current, the South Pacific and the South Pacific Con- 

 vergence regions and least in the South Atlantic (Scotia Sea) 

 region. 



21. The relatively few tows that caught exceptional numbers of B. 



abyssicola were made during the austml spring and summer 

 seasons in the convergence zones. 



22. The size- frequency composition of the sample population con- 



sists of a major peak at 31 to 47 mm mantle length and a second- 

 ary peak at 11 to 23 mm ML. 



23. The sex ratio of the total population is about 1:1, but males pre- 



dominate below 43 mm MTj and females greatly predominate 

 above 47 mm ML. 



24. A comparison of 3-meter IKMT catches reveals that tows in the 



Antarctic were three times more successful and caught ten times 

 the number of B. abyssicola than tows in the Gulf of Guinea. 



25. B. abyssicola is the most common pelagic cephalopod captured in 



Antarctic waters ; the vertical ranges and the relative abundance 

 of the three next most common species of oegopsids are com- 

 pared with those of B. abyssicola. The ranges of these species 

 overlap between 500-1000 m, but B. abyssicola replaces them 

 at greater depths. 



