McKenna; Trophic relationships of Antarctic demersal fish of South Georgia Island 



649 



Table 6 



Proportional prey overlap in the diets of 15 Antarctic demersal fish species collected off South Georgia I., based on the dry-weight 

 abundance of prey items in each species diet. Proportional similarity coefficient values are given in the upper subdiagonal of the matrix. 

 Variance of the proportional similarity coefficient values are given in the lower subdiagonal of the matrix. Values of >0.5 have been 

 underlined. 



ACER ARTE ELEG GIBB GUNN GUNT HANS LARS MICR NUDI PARA PSEU PSIL ROSS SQUA 



ACER 



ARTE 



ELEG 



GIBB 



GUNN 



GUNT 



HANS 



LARS 



MICR 



NUDI 



PARA 



PSEU 



PSIL 



ROSS 



SQUA 



0.1388 

 0.2576 

 0.0839 

 0.1009 

 0.2926 

 0.1426 

 0.1014 

 0.2215 

 0.1009 

 0.4035 

 0.3429 

 0.1009 

 0.3335 

 0.0437 



0.1665 0.7514 

 - 0.0460 

 0.0439 

 0.2522 

 0.1521 

 0.1505 

 0.1637 

 0.1697 

 0.1231 

 0.2804 

 0.1505 

 0.1505 

 0.1505 

 0.1874 

 0.1736 



0.0488 

 0.0438 

 0.2354 

 0.0856 

 0.0439 

 0.2041 

 0.0446 

 0.2904 

 0.2858 

 0.0438 

 0.2701 

 0.0425 



0.0924 

 0.3253 

 0.0514 



0.0468 

 0.0452 

 0.0919 

 0.1448 

 0.3968 

 0.2611 

 0.0845 

 0.0459 

 0.0452 

 0.1687 

 0.2610 



0.1139 

 0.1862 

 0.0459 

 0.0491 



0.1916 

 0.0841 

 0.2449 

 0.0209 

 0.2370 

 0.1713 

 0.2419 

 0.0039 

 0.2515 

 0.0432 



0.3723 

 0.1846 

 0.3043 

 0.0475 

 0.7416 



0.2333 

 0.2449 

 0.1994 

 0.2354 

 0.3629 

 0.4335 

 0.1916 

 0.4416 

 0.0416 



0.1575 

 0.1980 

 0.0896 

 0.0966 

 0.9073 

 0.7852 



0.2810 

 0.0938 

 0.2360 

 0.2130 

 0.2837 

 0.0841 

 0.3245 

 0.0883 



0.1145 

 0.2166 

 0.0460 

 0.1757 

 0.4286 

 0.4286 

 0.4661 



0.1663 

 0.3561 

 0.1713 

 0.2420 

 0.2449 

 0.3251 

 0.2472 



0.3311 

 0.2827 

 0.2798 

 0.5578 

 0.0213 

 0.2751 

 0.1008 

 0.2107 



0.1139 

 0.3434 

 0.0468 

 0.3111 

 0.6224 

 0.6208 

 0.6275 

 0.5561 



0.7878 0.7033 



0.3212 



0.2656 

 0.2215 

 0.2001 

 0.0193 

 0.3146 

 0.2233 



0.1716 

 0.2419 

 0.2354 

 0.2544 

 0.1720 



0.1846 

 0.6373 

 0.0930 

 0.2194 

 0.4778 

 0.2630 

 0.2194 

 0.3311 

 0.2200 



0.1566 

 0.1713 

 0.4038 

 0.0451 



0.1846 

 (1.6353 

 0.0482 

 0.4099 

 0.6683 

 0.4542 

 0.4106 

 0.2758 

 0.4099 

 0.8056 



0.2419 

 0.4640 

 0.0423 



0.1139 

 0.1846 

 0.0459 

 0.0475 

 0.9961 

 0.7416 



0.4819 

 0.2229 

 0.3833 

 0.1918 

 0.4929 

 0.7497 

 0.9073 0.5799 



0.4286 

 0.0197 

 0.6208 

 0.2194 

 0.4099 



0.2499 

 0.0416 



0.5165 

 0.4079 

 0.5270 

 0.5872 

 0.7433 

 0.4913 



0.0458 

 0.2043 

 0.0444 

 0.3132 

 0.0451 

 0.0435 

 0.0926 

 0.2948 

 0.2566 

 0.2170 

 0.0470 

 0.0442 

 0.0435 

 0.1531 



0.1393 



>39% Fish 



c 



^ 50% Knll 



Isopods & Amphipods 



Tunicates & Amphi pods 



PolyohaBt es & Gastro pods 



Amphipods & Polvchaetes 



0.1 



0.2 0.3 



0.4 



0.5 0.6 



Smul.inl v 



0.7 



ACER 

 PARA 

 PSEU 



FlSh- 

 eaters 



ELEG_ 



GUNN 

 PSIL 



GUNT 

 HANS 



Krlll  

 eaters 



LARS 

 ROSS 



ARTE I 



SQUA Benthic 



GIBB ' nve f 1 

 Feeders 

 I 



MICR 



0.8 



0.9 



Figure 2 



Dendrogram representing the classification of Antarctic demersal fish into 

 trophic groups based on numerical abundance of prey items in their guts. 

 Refer to Table 1 for key to species codes. Species grouped together within 

 a box were identified as having significantly similar diets. 



Parachaenichthys georgianus has a scaleless, elon- 

 gate body. Its mouth is tube-shaped and probably func- 

 tions like a slurp gun. It may be an ambush predator 

 like the C. aceratus. Its diet consisted mainly of fish 

 (59%) and roughly equal proportions of krill and shrimp 



(Table 3). None of the fish it consumed 

 were identifiable. Its diet overlapped most 

 (80%) with that of the Pseudochaenichthys 

 georgianus (Table 6). 



Pseudochaenichthys georgianus also 

 preyed heavily on other fish (59%)(Table 

 3). Like C. aceratus, it has a large mouth. 

 However, it tended to feed on smaller fish 

 and more krill than C. aceratus and did not 

 eat shrimp. It fed on a variety of other fish 

 species including N. larseni, C. gunnari, 

 M. microps, and Parachaenichthys georgi- 

 anus. Its diet overlapped most (80%) with 

 that of Parachaenichthys georgianus. 



D. eleginoides is the largest of all Antarc- 

 tic demersal fish, growing to over 2m, and 

 is an active predator (Fischer and Hureau 

 1985). It is known to be pelagic during 

 some stages of its life (Fischer and Hureau 

 1985), but the presence of rocks in a few 

 stomachs indicates that some had been 

 feeding close to the bottom. It fed almost 

 exclusively on fish (97%) (Table 3). Based 

 on identifiable fish in the guts, it preyed 

 on M. microps, N. larseni, Parachaenichthys georgi- 

 anus, and its own young. Stomachs from this species 

 often contained a single fish that was as much as 53% 

 of the size (TL) of the predator. Its diet overlapped 

 most (75%) with that of C. aceratus. 



