-37- 



G. Shipping Traffic 



There is considerable shipping traffic in the Drake 

 Passage by vessels too large to pass through the Panama 

 Canal. Commercial shipping, including oil tankers, passes 

 through that area, usually north of the Antarctic Conver- 

 gence which lies about midway between South America and 

 the Antarctic Peninsula in the Drake Passage. In addition 

 scientific vessels and commercial fishing vessels are found 

 throughout the southern ocean at various times of year. 

 Relatively few vessels penetrate the pack ice zone. 



H. Ecosystem Responses to Disturbance 



Even though the Antarctic marine ecosystem is relatively 

 undisturbed in comparison with other oceanic regions, it is 

 not a pristine area by any means. There has been harvesting 

 of seals, whales, fish, krill, and penguins. Whaling has 

 had the largest impact on stocks, with the populations of baleen 

 whales drastically reduced from levels of a century ago. 



Because baleen whales consume enormous quantities of 

 krill during the summer season, the reduction in whale numbers 

 has reduced the impact of whale predation on krill populations 

 and has allowed more krill to become available to other pre- 

 dators. There is evidence that other populations within 

 the ecosystem are adjusting to the changing abundance of 

 whales. Penguin populations are increasing (Conroy, 1975) 

 and there is evidence that seal populations are increasing 

 also (Laws, 1977b). It is clear that the whale populations 

 themselves are changing. Both population size and age at 

 sexual maturity are different from original stock levels 

 (Gambell, 1976; Laws, 1977a). 



The Antarctic marine ecosystem as well as the Antarctic 

 continent have been used as a scientific laboratory. Data 

 on the biology of the Antarctic marine ecosystem come from both 

 scientific and commercial investigations. Carefully controlled 

 harvesting with good data reporting can create an opportunity 

 for a controlled experiment on the Antarctic marine ecosystem 

 which can provide a great deal of information about its 

 biology. 



I . Potentially Harvestable Resources 



An ecosystem viewpoint is a necessary perspective on the 

 ecology and management of renewable resources in Antarctic 

 waters. There are many potentially harvestable resources: 

 fish, squid, seals, whales, krill and possibly birds. These 

 populations are not independent but are closely related. 



