C-20 



Antarctic than fin whales. Present annual consumption of 

 krill by whales is approximately 42 x 10^ million tons 

 (Laws, 1977), less than half of the total consumption by 

 seals and also less than consumption by squid. 



Sperm and killer whales are present in the Antarctic 

 ecosystem, but do not consume krill directly. They eat 

 fish and squid and are one step removed from krill in the 

 food chain. 



Data on whales are based on fishery statistics and 

 are very good estimates of population size and consumption 

 rates. Seal information is almost reliable as that of 

 whales. Both aerial and shipboard techniques have been 

 used to estimate seal populations. 



In Figure 2, phytoplankton production and bird, seal 

 and whale standing stocks are the most reliable numbers. 

 Krill and other zooplankton estimates are considerably less 

 reliable. Fish and squid estimates are the softest numbers 

 in the table, essentially educated guesses. 



Predation Table 



Figure 3 shows estimates of the total biomass flowing 

 along the arrows of the conceptual model of Figure 1. 

 Values are in units of 10° tons and represent annual totals 

 for the area south of the Convergence. Flows are located 

 with the donor compartment as column heading and the recei- 

 ver compartment as row heading. Flow from krill to penguins, 

 which represents consumption of krill by penguins, is in the 

 krill column and penguin row of the matrix and is 14.4 x 10" 

 tons per year. 



Ice algae production is about 5% of phytoplankton pro- 

 duction (Green, 1977). Ice invertebrates feeding on ice 

 algae provide a mechanism for putting that carbon into the 

 water column. Zooplankton and fish larvae eat ice algae. 

 For the higher trophic levels , the matrix has been derived 

 from the predator perspective. 



Estimates of predation on krill by fish, squid, pen- 

 guins, seals, and baleen whales were documented in the dis- 

 cussion of Figure 2. Consumption of other zooplankton, 

 fish, squid, and birds are from Green (1977), Laws (1977) 

 and Prevost (in press). 



Bird and mammal consumption rates are based on exten- 

 sive data. Fish and squid consumption rates are specula- 

 tive . 



