184 U.S. NATIONAL MUSEUM BULLETIN 291 



Table XV.— Seasonal and regional occurrence of the 16 tows that caught 9 or more 



specimens per 2-hour tow 



Elt. Sta. 



Number 



99 



1201 



1262 



1269 



248 

 1287 

 1324 

 1327 

 1328 



846 



847 



858 

 1364 

 1383 



354 



382 



in the Scotia Sea region with the poor success to unsuccessful ratio of 

 6 to 20 or only 23% successful. This region has been shown to be 

 sparsely populated with B. ahyssicola, so the low success may be related 

 to area. On the other hand, Cruise 9 covered the same general area 

 in August and September and it scored an 8:7 success ratio (53%), 

 still fairly low in comparison w^th other areas, but it may indicate 

 an increase in abundance during the austral spring. Unfortunately, 

 no further data are available for this region. The remaining winter 

 tows were made in the Drake Passage and the South Pacific and these 

 amounted to 14 successful tows and 7 unsuccessful tows for a 66% 

 success rate, equally as successful as spring and summer tows. 



It appears then that B. ahyssicola can be caught with about the 

 same frequency of success in most regions of the Antarctic during 

 most of the year. But the data suggest that more individuals are 

 present during the austral spring and summer or at least that they 

 tend to congregate in patches in the region of the convergence. This 

 suggests a correlation with the spring-summer peak of high organic 

 productivity in the surface waters of the Antarctic Ocean. 



No evidence exists to suggest that there are significant differences 

 in the size of B. ahyssicola over the seasons. Specimens of all sizes 

 and all stages of maturity have been taken throughout the year; often 

 specimens that range from larvae through juvenile and maturing 

 stages, to ripe and spent individuals occur in the same trawl-haul. Few 

 tows tliat catch more than 2 or 3 specimens have all individuals of the 

 same size or stage of maturity, unless they are shallow tows which 

 tend to have predominantly larvae and juveniles. The 16 tows that 



