-39- 



that although sei whale populations remained fairly 

 constant in the early seventies, population models used 

 to describe this population's characteristics may not 

 adequately represent its actual population dynamics. 

 Population adjustments may have resulted from declines in 

 other baleen whales and changed interactions with those 

 species. The changes, which may include expanded sei 

 whale feeding grounds and an increase in overall abundance, 

 will be discussed later. 



e. Feeding Habits 



The quantities and type of food consumed by baleen 

 whales in the Antarctic has received much attention 



(Mackintosh and Weller, 1929; Hardy and Gunther, 19 35; 

 Peter, 1955; Marr, 1956; Nemoto, 1959, 1962; Banister and 

 Baker, 1967; Laws, 1977a, 1977b) . Tables 6 and 7 present 

 information on relative biomass and variety of food items 

 consumed by whales in the Southern Ocean. Krill seems to 

 be the main food for blue, fin, humpback, and minke whales 



(Mackintosh, 1965). About 80% of the blue, fin, and 

 humpback whale diet is krill. It is all consumed during the 

 whales' 3 to 5 month austral siommer feeding period 



(Mackintosh 19 70) . Sei whales are somewhat less dependent 

 on krill and it may account for less than half their diet 



(Mackintosh, 1970) . But, since the serious decline of other 

 whales, sei whales have been moving farther south into 

 heavy krill zones where other whale species formerly fed 

 and now may be eating more krill (Nemoto, 1962) . Minke 

 whales, with a current estimated total biomass of only 1.4 

 million tons, consume more krill than any other baleen whale 

 in the Antarctic (Laws, 1977a). One reason for this high 

 level is that minke whales presumably remain south of the 

 Convergence all year long while other baleen whales are 

 south of the Convergence only during their intensive feeding 

 period. 



Food habits of different Antarctic baleen whales re- 

 flect several factors, including food distribution, 

 morphological characteristics of the whales' feeding 

 apparatus, individual species' feeding behavior, and the 

 presence of other whales and competitors. Comparing blue, 

 fin, and sei whales, one notes a trend of feeding areas with 

 sei whales in the more northerly areas, fin whales a little 

 further south, and blue whales the farthest south (Gulland, 

 1974). Food items taken by the different species varies 

 also. Blue whales eat Euphausiids primarily, fin whales 

 euphausiids and copepods , and sei whales mainly copepods 

 (Nemoto, 1970) . The three species each have a character- 

 istically different feeding apparatus representing different 



