The diet of the Subantarctic fur seal (Arctocephalus tropicalis) at Marion Island

Abstract

Faecal analysis (n = 804 scats) was employed to examine the diet of the Subantarctic fur seal Arctocephalus tropicalis at Marion Island over a period of seven years (2000 - 2006). Despite the biases associated with the method, useful information was gained on seasonal and inter-annual fluctuation in the presence of prey species in the diet1 2. The indices used to investigate these variations were percentage numerical abundance, percentage presence and reconstituted body size (mass and length) of prey species taken. The diet was diverse and myctophid species predominated. Cephalopods were minor prey species (n = 39 scats). The five main prey species were Gymnoscopelus bolini, G. piabilis; G. fraseri; G. nicholsi and Protomyctophum tenisoni. In all respects G. bolini predominated throughout the study period, although in most comparisons no statistically significant differences in the relative contribution amongst the main prey species in the diet were found. Seasonal and inter-annual variations in the contributions of these species to the diet presumably resulted from changes in the relative abundance and distribution of prey3. Future research will attempt to relate this variability to environmental variability4.