THE DIET OF THE ANTARCTIC TOOTHFISH IN THE ROSS SEA

This brief review documents the species composition of prey consumed by the Antarctic toothfish, Dissostichus mawsoni, in the Ross Sea. The diet for a sample from McMurdo Sound in the southwestern Ross Sea indicates that fishes, especially Pleuragramma antarcticum, and mysids dominate the diet by both frequency of occurrence and dry weight. P. antarcticum is 71% by occurrence and 89% by weight; the corresponding figures for mysids are 60% and 11%. Channichthyids (icefishes) are the second most abundant prey fish. Farther north on the shelf edge and slope, fishes and cephalopods (squid) are the most frequently consumed prey groups at 78-86% and 5-14%, respectively. Pleuragramma are absent from the warmer slope waters and thus prey fishes were other notothenioids and non-notothenioids. Channichthyids and the macrourid (grenadier or rattail) Macrourus whitsoni dominated the diet at 54% and 37%, respectively. In the deep oceanic waters (60-70°S) north of the shelf break the diversity of pelagic and epipelagic fishes is low. Here the diet of D. mawsoni consists of relatively small squid of at least six different genera. It can be concluded that D. mawsoni is a generalized piscivorous predator that feeds primarily in the water column and occasionally on the substrate. There is variability in the diet within Subarea 88.1 that reflects the abundance of various species of prey fish within the shelf, slope and oceanic communities of the Ross Sea.