DANIELS: FEEDING ECOLOGY OF ANTARCTIC FISHES 



Pleuragramma antarcticum was observed under 

 fast ice in schools of several thousand individuals 

 on three occasions. Individuals darted about and 

 frequently approached the ice-water interface 

 where they appeared to bite at and consume 

 small amphipods {Nototropis sp.). Individual 

 juvenile T. neumesi also entered the water col- 

 umn under an ice cover or during other periods 

 of low light intensity. These fish generally were 

 found in shallow-water brown algae, Desmeristia 

 anceps, beds except when ice was present and 

 light conditions were favorable. They then left 

 the beds individually and occupied the water 

 column where they fed on the undersurface of 

 the ice, or the substrate or in the column. On one 

 occasion, one large N. neglecta (400 mm SL) en- 

 tered the water column and ate several P. antarc- 

 ticum from a school before returning to a rock 

 outcropping. Fishes using this feeding method 

 usually fed upon motile invertebrates, such as 

 eupausiids, pteropods, and amphipods, or other 

 fishes often associated with the pelagic or 

 cryopelagic communities. 



Grazing, although never observed, appeared 

 to be an important feeding method in some spe- 

 cies, most notably TV. neglecta, during spring and 

 summer. Individuals were collected with large 

 sheets of macroalgae (e.g., Phyllogigas grandi- 

 folius, Iridaea obovata, or Desmeristia spp.), 

 solitary, epiphytic diatoms (Trigonium acticum, 

 Cocconeis imperatrix, Amphora sp., Grammato- 

 phora sp., Licmophora sp., and Achnanthes sp.), 

 and epibenthic diatoms (Biddulphia anthropo- 

 morpha, Melosira sol, Amphora sp., Grammato- 

 phora sp., Licmophora sp., Achnanthes sp., and 

 Isthmia sp.) in their stomachs. 



It was inferred from stomach contents that 

 fishes commonly switched from one feeding 

 method and/or foraging area to another with 

 season. Notothenia neglecta ambushed prey from 

 rock outcroppings and algae beds through much 

 of the year. During the spring and summer 

 plankton blooms, however, some individuals be- 

 gan to search for food on homogeneous mud bot- 

 toms away from any protective rock crannies, as 

 evidenced by large numbers of mud-bottom iso- 

 pod Serolis polita in some stomachs in Decem- 

 ber. During spring and summer, individual N. 

 neglecta cropped macroalgae and harvested 

 diatom mats from mud and gravel bottoms. Noto- 

 thenia gibberifrons used the slurp feeding meth- 

 od to forage in more northern areas but am- 

 bushed its prey in southern areas (Daniels and 

 Lipps 1978). 



Diets 



Diets varied among the 14 species examined so 

 that fishes could be ranked from specialized 

 feeders to feeding generalists (Tables 2, '.I, 4). 

 Seven species were generalists (high P and H) 

 and seven species were specialists (low Pand //). 

 Generalists consumed a variety of organisms 

 which were phylogeneticly and morphologically 

 distinct. Specialists preyed upon organisms with 

 similar morphologies or in the same prey taxon. 

 There appeared to be two types of specialists: in 

 one group, Cryothenia peninsulae, Harpagifer 

 bispinis, Artedidraco skottsbergi, and Parachaen- 

 ichthys charcoti, the diet consisted largely of 

 organisms from one prey taxon; while in the 

 second, Trematomus newnesi, Pleuragramma 

 antarcticum, and Prionodraco evansii, relatively 

 few prey taxa were consumed in approximately 

 equal numbers. Although quantitative data on 

 food availability were not collected, generalists 

 also appeared to be feeding opportunists that ate 

 the most abundant available prey. Individuals in 

 the generalist species also tended to be general- 

 ists. Individual N. neglecta commonly consumed 

 prey from 5 to 10 taxa (87% of sample) and most of 

 the available prey in the algae beds of Arthur 

 Harbor (Lowry 1969) were found in stomachs of 

 N. neglecta. Specialists tended to be more selec- 

 tive. In the rubble bottom community where H. 

 bispinis was collected, gastropods, small echino- 

 derms, and errant polychaetes were abundant, 

 yet, except for the scaleworms, which became 

 seasonally important, were rarely found in H. 

 bispinis stomachs. Individuals in the specialist 

 species also tended to be specialists; 91% of the 

 H. bispinis examined had consumed prey from 

 one or two taxa. 



Amphipods were the prey item most fequently 

 taken by fish (Tables 2, 3, 4). However, they were 

 the most important component by volume in only 

 H. bispinis and A. skottsbergi. Polychaetes were 

 also frequently consumed and were an important 

 part of the diet of N. nudifrons, N. larseni, T. 

 scotti, and A. skottsbergi by both number and 

 volume. Isopods, gastropods, and pelecypodsalso 

 occurred consistently, but were relatively minor 

 components in most diets. Other taxa were im- 

 portant dietary items for only particular species 

 or at particular times of year. Euphausiids, 

 Euphausia superba and E. chrystallorophias, 

 dominated the diets of N. larseni, T. scotti, T. 

 neumesi, T. bernacchii, Pleuragramma antarc- 

 ticum, and C. peninsulae by number and volume. 



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