-4- 



All of the breeding stocks for each species of concern 

 should be maintained in a robust condition. In the Antarctic 

 as in other ocean areas, there are natural variations in 

 climate which have negative effects on populations. Unusually 

 warm years, in which pack ice extent is very limited, occur 

 occasionally. These may affect the productivity of plants, 

 and the food supply for zooplankton, fish and birds. In 

 addition some populations may become more vulnerable to 

 predators. Acceptable breeding habitat for seals may 

 be limited. Unusually severe weather, such as prolonged 

 blizzards, may kill all the young of the year for an 

 entire bird rookery. In an undistrubed state, populations 

 can recover from bad years. The size of the breeding 

 stocks of each species should not be reduced to marginal 

 levels where recovery from an unusual year would be slow. 



For the Antarctic marine ecosystem to remain healthy, 

 its overall productivity should be maintained. The balance 

 between populations and hence the structure of the 

 ecosystem should be maintained both in the system as a whole 

 and in local areas. The inherent resilience of the system, 

 that is its ability to recover from bad years, should not 

 be endangered. 



2. Conservation Objectives 



In addition to maintaining the health of the Antarctic 

 marine ecosystem, other tenets of the proposed federal 

 action include preventing the overexploitation of any 

 Antarctic marine living resource and ensuring that any 

 harvesting of one species does not adversely affect the 

 health of dependent or related species. 



Understanding of the biology of the Antarctic marine 

 ecosystem is incomplete. Populations of whales are best 

 known , although information is by no means complete. 

 Estimates of abundance, growth and reproduction, and mor- 

 tality rates are available for the harvested species. 



There is less current information on protected 

 species in the absence of data provided by commercial 

 catches. Abundance estimates are available for seals, but 

 vary over wide ranges. Some information on reproductive 

 rates is also available. However, very little is known 

 of the distribution or survival rates of juveniles, and 

 consequently recruitment into the breeding population 

 cannot be predicted. Since most birds congregate on 

 islands or the coast of the Antarctic continent for breeding, 

 abundance estimates are available for the species and 

 rookeries which have been studied. 



