H-28 



RESEARCH PROGRAMMES 



colonial birds, the major limiting factor may be availability of nest sites, there is evidence 

 indicating that food availability is still an important factor. In terms of food consumption, 

 birds and large whales are each estimated to take about 40 million tons annually while seals 

 take about twice as much--80 million tons. OriginaUy the large whales were estimated to have 

 taken nearly 200 million tons annually of krill, squid and fish before their stocks were depleted 

 by whaling. 



The staggered southerly migration of baleen whales and their feeding preferences for 

 different class sizes of krill and other zooplankton reduce competition. However, it has been 

 demonstrated that longitudinal segregation also occurs with the larger and older whales arriving 

 first to occupy certain areas of the feeding grounds, and younger, later arrivals being displaced 

 to the periphery (Laws, 1960). At South Georgia, for example, where the different species 

 overlap, competition for krill of the same size occurs. The growth and pregnancy rates 

 of Blue and Fin whales have increased and the mean age of sexual maturity has decreased 

 during the periods of expanding whaling operations in response to increased food abundance 

 (Laws, 1977 and in press). Similar increases in pregnancy rates and advancement of maturity in 

 Sei Whales have been shown to precede large scale exploitation of the species, and so could not 

 be a direct result of hunting. This lends support to the belief that the increased early 

 pregnancies and growth rates are indirect responses to whaling through its effect on food supply. 



There is no direct evidence of a change in abundance of krill-eating Crabeater Seals, but 

 there is evidence of an increased rate of reproduction. Their mean age of sexual maturity in 

 Whaling Zone I (the Sanctuary) has decreased from 4 years in 1955 to 2.5 in 1970 during a 

 period of rapid depletion of whale stocks (Laws, 1977). At South Georgia the population 

 explosion shown by the krill-feeding Fur Seal Arctocephalus gazella is very marked and other 

 colonies are developing in the Scotia Arc. Their distribution overlaps the baleen whale feeding 

 distribution and the much more rapid recovery of -4. gazella in comparison with y4. tropicalis 

 can probably be attributed to changes in krill availability. 



2.5.4 Objectives. 



The objectives of the programme will be: 



1. Identification of unit breeding or management stocks, their location, movements and 

 possible mixing. 



2. To obtain full data by species, sex, age and size for all catches. 



3. Stock assessment and the estimation of potential yields when appropriate. 



4. An understanding of trophodynamics. 



5. An understanding of interactions between whales, seals and birds and with other 

 groups at a similar trophic level, such as fishes and squids. 



6. Formulation of suitable management and conservation procedures. 



Objective 2 is being met under schemes operated by the Bureau of Whaling Statistics, and 

 in respect to seals and birds by the Antarctic Treaty (Agreed Measures for the Conservation of 

 Antarctic Flora and Fauna). The Convention for the Conservation of Antarctic Seals calls for 

 reporting of catches. 



2.5.5 Research programmes 



1. The mapping of seasonal pack ice distribution and type is particularly important in 

 extrapolating sample seal densities to larger areas and, again primarily for seals, in assessing the 

 significance of residual pack ice regions in summer for the separation of stocks. (Objectives 1 , 2 

 and 4) 



2. Research should be carried out throughout the range of species including, for whales 

 and birds, the winter period outside the Southern Ocean. 



