The diet of Antarctic fur seals around Heard Island was investigated in May and June 1990. Fish predominated in samples, occurring in an average of 93.4% of droppings. Otoliths from pelagic fish (mainly myctophids) constituted over 96% of all otoliths. There was an increase in the occurrence of squid from 3.4% in summer 1987/88 to 49.3% in the present study. For the fish species Gymnoscopelus nicholsi (Gilbert), 10.3% of otoliths recovered from scats were considered suitable for measurement compared with 30.5% from scats at Heard Island in 1987/88; this greater level of erosion provides further evidence that the seals were foraging further afield. The study demonstrates a significant difference between summer 1987/88 and winter 1990.

Between September 1987 and February 1988, Antarctic fur seals Arctocephalus gazella (Peters) at Heard Island fed mainly on fish with an average 95.2% of scats in monthly collections containing fish remains. Pelagic myctophids constituted more than 50% of fish taken by fur seals at the beginning of the summer season and again at the end when there was an influx of non-breeding male seals. During the middle period from October to December, fish from the surrounding shelf area comprised the bulk of the diet. These included various benthic nototheniid species, the bentho-pelagic ice fish Champsocephalus gunnari Lönnberg and skate (Bathyraja spp.), the latter being found in over 60% of scats in October and November. The population of Antarctic fur seals at Heard Island is increasing at about the same rate as at South Georgia. There the increase is thought to be due to the high availability of krill E. superba, but in the present study no euphausiid remains were found, so the increasing population at Heard Island has been supported on a diet of fish. Whether this population increase can be sustained in future on a diet of fish is arguable. Trial fishing around Heard Island indicates that one of the major dietary items of the seals (C. gunnari) is of probable commercial importance and therefore any plans for the establishment of a fishery on Heard Island grounds must be considered in this light.

Icefish (Champsocephalus) were taken as bycatch during krill fishing operations from a research vessel. The data indicate that the bycatch of fish in the commercial krill fishery may be significant in some areas of the South Georgia shelf. The problem is thought to be least in open ocean krill fishing.

The occurrence of fish in the diet of the Antarctic fur seal (Arctocephalus gazella) at Bird Island, South Georgia was investigated by analysis of fish otoliths in scats (faeces) collected during late May to early November 1983. Of the 55 scats examined, 49 contained fish remains, and 45 contained fish otoliths. Ten fish species were represented by 415 otoliths, and 33 otoliths were too digested to be identified unequivocally. Fish size was estimated from otolith size based on published allometric equations. Four coastal notothenioid fishes dominated the fish component of the diet: Champsocephalus gunnari and Gobionotothen gibberifrons each comprised about 40% of the total fish mass; Chaenocephalus aceratus was ranked third by mass and the smaller Lepidonotothen larseni occurred in one quarter of the scats but was of lower importance in terms of mass. The length-frequency distribution of C. gunnari landed by the commercial fishery in October 1982 to June 1983 is similar to that which comprised the bulk of the diet in the present study. Compared with recent studies on the fish component of the diet in the literature, the dominance of C. gunnari is generally similar, however, there was a greater proportion of G. gibberifrons during the 1983 winter and spring than reported for recent winters.

During the last decade, methods for detecting DNA polymorphisms have proliferated at a bewildering pace. Today the investigator must choose among various types of genetic markers as well as between a variety of methods for discovering and screening polymorphisms. Polymorphisms useful for the analysis of population structure are found in both mitochondrial and nuclear genomes. Marker development may proceed along two routes: 1) discovery of species–specific markers, and 2) application of universal methods. Species-specific markers are based on sequence data from the target species or close relatives, whereas universal markers are based on the use of polymerase chain reaction (PCR) primers targeted to regions highly conserved across diverse taxa. Markers commonly employed include mitochondrial DNA polymorphisms, microsatellites, anonymous nuclear loci and known genes (both coding and noncoding regions). Methods for detecting polymorphisms range from technically simple (RFLP analysis) to more sophisticated mutation scanning methods. We review the application of these approaches to several key Antarctic species (the Patagonian toothfish Dissostichus eleginoides, the mackerel icefish Champsocephalus gunnari, and the squid Martialia hyadesi Rochebrune & Mabille, 1889) and present preliminary data on genetic polymorphisms in toothfish and icefish.