650 



Fishery Bulletin 89(4). 1991 



>50%FISH 



50%-100% Kflll 



Isopods & polychaetes 



Polychaeles & Gastropods 



Fish & Polychaetes 



GIBB Benthic 



Mirn lnvert 

 MICR Feeders 

 SQUA 



0.1 



0.2 



0.3 0.4 



0.5 0.6 

 Similarit \ 



0.7 



0.8 0.9 



Figure 3 



Dendrogram representing the classification of Antarctic demersal fish into 

 trophic groups based on dry weight of their gut contents. Refer to Table 1 

 for key to species codes. Species grouped together within a box were iden- 

 tified as having significantly similar diets. 



Krill-eaters 



Seven species were grouped as krill-eaters. The hier- 

 archical cluster analysis places C. gunnari, P. brevi- 

 ceps, and P. hansoni in a single cluster and identifies 

 others within this group as distinct clusters. The cluster 

 analysis arranged these species in order of decreasing 

 proportion of krill in the diet (Fig. 3, from top to bot- 

 tom). These species are probably more pelagic in nature 

 than other members of the community, with the pos- 

 sible exception of N. nudifrons (Permitin and Tarver- 

 diyeva 1972, Targett 1981). 



C. gunnari and P. breviceps had the most similar 

 diets (Table 6), feeding almost exclusively (>97%) on 

 krill. Psilodraco breviceps diet consisted 100% of krill 

 (Table 3), but only three specimens were examined and 

 the true variability of this species' diet may not be ac- 

 curately represented here. 



Champsocephalus gunnari is the most important 

 commercial species around South Georgia (Kock 1986, 

 Gabriel 1987, McKenna and Saila 1989). It leads a more 

 pelagic existence than its local relatives (C. aceratus, 

 P. georgianus) (Kock 1985b). Its heavy dependence on 

 krill has been documented (Targett 1981, Permitin and 

 Tarverdiyeva 1972, Permitin and Tarverdieva 1979, 

 Tarverdiyeva and Pinskaya 1980, Kock 1981). In this 

 sample, its diet was composed almost entirely (99%) 

 of krill (Table 3). 



Little is known about the life history of P. hansoni, 

 except for its heavy dependence on krill (Targett 1981). 



In 1987-88, its diet consisted primarily of 

 krill (91%), but it also fed on fish and 

 tunicates (Table 3). Its diet overlapped 

 those of C. gunnari and P. breviceps by 

 more than 90% (Table 6). 



Patogonothen brevicauda is endemic to 

 a shallow shelf region west of South Geor- 

 gia known as Shag Rocks. Its diet con- 

 sisted of 80% krill and 20% fish (Table 3). 

 Its diet overlapped that of four other spe- 

 cies (C. gunnari, P. hansoni, P. breviceps, 

 and N. rossii) by more than 70%, due to 

 the heavy dependence on krill (Table 6). 

 Nototheniops nudifrons is thought to be 

 benthic in nature (Targett 1981, Permitin 

 and Tarverdiyeva 1972, Permitin and 

 Tarverdieva 1979). However, in 1987-88, 

 66% of its diet consisted of krill (Table 3) 

 and the remainder was composed of epi- 

 benthic invertebrates. Rocks accounted for 

 about 0.5% of the average dry-weight con- 

 tents. Its diet overlapped that of four other 

 species (C. gunnari, P. brevicauda, P. han- 

 soni, and P. breviceps) by 62% (Table 6). 

 Notothenia rossii is a large (90 cm) spe- 

 cies that was the mainstay of the commer- 

 cial catch during the early 1970s (Kock 

 1986). Its diet was diverse, but it was grouped with the 

 krill-eaters because 46% of its food was krill (Table 3). 

 Fish was the second-most-important item in its diet and 

 included Parachaenichthys georgianus, M. microps, 

 P. hansoni, and iV. larseni. Notothenia rossii'?, diet 

 overlapped most (74%) with those of Pseudochaenich- 

 thys georgianus and P. brevicauda (Table 6). 



Nototheniops larseni is considered to be one of the 

 most pelagically adapted of the nototheniids (Targett 

 1981). Previous work has shown that its diet is often 

 dominated by krill (Permitin and Tarverdyieva 1972 

 and 1979, Targett 1981, Daniels 1982). In this study, 

 krill comprised only one-third of its diet, and 56% was 

 pelagic tunicates and amphipods (Table 3). Its diet 

 overlapped that of N. nudifrons by 55% (Table 6). 



Consumers of benthic invertebrates 



All of the members of the 'benthic invertebrate feeders' 

 group had diets which were distinct from one another 

 as well as from members of the other major groups. 

 However, these fish all seemed to be closely associated 

 with the bottom. 



Notothenia squamifrons diet was the most unusual 

 of all the species examined. It included a large propor- 

 tion (49%) of tunicates (salps) (Table 3). The remainder 

 of its diet consisted almost entirely of benthic inver- 

 tebrates. Krill made up only 4%. The preponderance 



