4o8 DISCOVERY REPORTS 



(1939), for instance, reports a scattered population of blues and fins frequenting the west Graham 

 Land channels from June to September 1921, the records of baleen whales killed during the winter 

 whaling that used to be carried on at South Georgia suggesting that the over-wintering population 

 is not altogether an insignificant one, and that of the Antarctic whale population as a whole it is 

 principally the blues and fins that overwinter.^ It is interesting, too, to record that whales are some- 

 times obliged to overwinter. Taylor (1957), for instance, reports the recent trapping of minkes in ice 

 pools on the Graham Land coast, while Porsild (191 8) describes a similar trapping of schools of 

 narwhals and white whales, and even an occasional humpback, in Disko Bay, stating that the pheno- 

 menon had been known for over 200 years and was by no means rare. 



The gross distribution of the staple whale food is shown by seasonal symbols in Fig. 142, the 

 symbols employed in this instance representing catches of not less than 1000 in the stramin nets, 

 the higher order of abundance being chosen with a view to investing the seasonal distribution and 

 relative abundance of this important class, the staple diet of whales, with the fullest possible signi- 

 ficance. Catches of less than 1000 are distinguished as before by small black plots throughout the 

 year. The principal facts thus illustrated may be summarised as follows: 



(i) The paramount importance of the East Wind-Weddell surface stream as the principal carrier 

 of the massive concentrations of older adolescents and adults, euphausians over 20 mm. long, that 

 are the staple diet of the whales. 



(2) The pronounced abundance of such concentrations that is found in this system in summer and 

 the absence or relative scarcity of them that is found, in the northern zone at least, in autumn and 

 winter. 



(3) The insignificance, most pronounced in the Pacific sector, of the West Wind drift as a staple 

 feeding-ground for the whales. 



(4) The absence or conspicuous scarcity of the staple feed in a large area of the Atlantic East Wind 

 zone between 30° W and 30° E, an area which might be supposed to be an eddy or backwater separating 

 the west-flowing from the east-flowing stream. 



(5) The absence of adolescent and adult krill from the wide expanse of shelf water at the head of the 

 Ross Sea. 



(6) The vast area of the principal region of staple abundance which in the depth of winter is 

 encompassed by the polar pack. 



Gross distribution of the total euphausian surface population 



The gross distribution and relative abundance of the total euphausian surface population is shown 

 in Fig. 143. Using the gatherings (larval, adolescent and adult) of the stramin nets in their 

 entirety, this figure is based as before (p. 349) on the combined observations of every southern cruise 

 that has been made since these operations first began. While it emphasises primarily the overriding 

 importance of the East Wind-Weddell surface stream as the principal carrier of the total population 

 it distinctly suggests that, as a feeding-ground, or potential feeding-ground, the East Wind drift, 

 although of manifest importance, ranks only second to the lower latitude region of euphausian 

 abundance in the northern or Weddell zone. The disparity however, though apparent, is largely 

 unreal. For in the ice-free parts of the northern zone sampling can be carried on all through the year, 

 the gatherings of the total population in consequence becoming enormously swollen with the masses 

 of older Calyptopes, and of Furcilias and early adolescents as they successively appear in the plankton. 



* In 5 years of winter (July-September) whaling at South Georgia, covering the years 1914-18, 930 baleen whales 

 were killed, an average of 186 every winter. The vast majority were blue and fin, only five being humpback (Risting, 

 1927). 



