-43- 



a. Distribution 



These seals have a circumpolar distribution (Figures 13, 

 14, 15, 16). Crabeater, leopard, and Ross seals use pack 

 ice principally whereas Weddell seals are usually found in 

 fast ice areas adjacent to the continent, ice shelves, and 

 offshore islands. 



1) Crabeater Seals 



Crabeater seals appear to prefer being relatively close 

 to the ice edge in cake and brash ice of 7 to 8 octas con- 

 centration (Gilbert and Erickson, 1977) . Siniff et al. (1970) 

 and Erickson et al. (1971) showed the relationship between 

 crabeater seal distribution and the ice type selected. These 

 authors found that seals selected unconsolidated pack ice 

 covering between 30% and 70% of the water surface. 



Concentrations of subadult crabeater seals observed by 

 Siniff et al. (1977b) may have broad biological significance 

 since similar crabeater concentrations have been previously 

 observed, but perhaps not understood in the context of what 

 they actually represented. Laws and Taylor (19 57) reported 

 a major die-off of crabeater seals and assumed that it was 

 caused by a viral infection. Solyanik (1964) also reported 

 a concentration of up to 3,000 crabeater seals. Lindsey 

 (1938) described concentrations of crabeater seals in fast 

 ice in the Bay of Whales in 1934. If concentrations of crab- 

 eater seal subadults are more prevalent than previously 

 thought, it may be that young individuals from large areas 

 of pack ice concentrate in the areas and feed as a group near 

 continental areas or offshore islands. Localized concentra- 

 tion areas may, therefore, be critical to crabeater seal 

 stock stability over a wide area, and disruption or harass- 

 ment of seals in concentration areas may be particularly 

 harmful. 



2) Leopard Seals 



Leopard seals are normally found in areas dominated by 

 cake and brash ice between 60° S. and 80° S. although 

 occasionally individuals have strayed to the southern tips of 

 Africa, South America, Austrialia, and New Zealand. Normally 

 solitary in pack ice, they sometimes concentrate on sub- 

 antarctic islands (Kemp and Nelson, 1931; Marr, 1935, 

 Hamilton, 1939; Bechervaise, 1962) . Gilbert and Erickson 

 (1977) showed a close correlation between leopard and crab- 

 eater seal densities and suggested that in addition to the 

 physical characteristics of the ice flows, predation on 

 crabeaters contributed to this high correlation. 



