Trophodynamics of the Antarctic toothfish (Dissostichus mawsoni) in the Antarctic Peninsula Subarea 48.1: prey composition and fatty acids profile

The Antarctic toothfish is the largest notothenioids species in the Southern Ocean, playing a key ecological role in the trophic web, as food source for marine mammals, and as top predator in deep-sea ecosystems, structuring the population dynamics of its prey through a trophic cascade. Most ecological information on this species rely on samples from areas where direct fishing is allowed by CCAMLR, whereas in areas such as the Antarctic Peninsula (AP), where it is prohibited, there are still important gaps. Here we characterize the trophic ecology of Antarctic toothfish in the northern tip of the AP, based on a combination of dietary morphological identification of prey composition and fatty acid analysis from samples collected in two seasons (2020-2021). From the 159 stomachs sampled, results showed that the diet of D. mawsoni was mainly composed of Macrouridae (24.75 IIR %), Anotopteridae (2.66%IIR) and Channichthyidae (2.26%IIR) with other prey items such as Cephalopods (8.42%) as relatively important items. Other rare groups found were crustaceans and penguin remains. Prey composition did not vary between years, sexes and sizes classes. On the other hand, based on a total of 27 fatty acid profiles identified, we observed two statistically different prey groups of fishes (Anotopteridae-Macrouridae-Channichthyidae) and cephalopods. These results provide important information to improve our understanding of the trophic dynamics of this species, its generalist feeding behavior probably consuming the most abundant prey, and updated information on its benthic-demersal ecological role in the AP, highly relevant for its ecosystemic fisheries management