Activity budgets for the sedentary Argentine sea bass Acanthistius patachonicus inferred from accelerometer data loggers

The amount of energy an animal uses to move may constitute a significant fraction of its energy budget, so detailed descriptions of wild animal activity budgets can help to understand the ecology of a species, both at the individual and at the population levels. The rocky-reef fishes inhabiting the northern Patagonian gulfs of Argentina are important economic and recreational resources for which no activity or energy budgets are available. This fish assemblage may reach high aggregated biomasses (exceeding several hundreds of kilogrammes of fish distributed along a few hundred metres of linear reef ledges) and is not clear how such biomasses can be supported by the low productivity of the Patagonian coastal waters. We used animal-attached accelerometers to characterise the behaviours and activity budgets for the most abundant and ubiquitous species of this assemblage, the Argentine sea bass or Mero' Acanthistius patachonicus (Jenyns, 1840; Osteichthyes: Serranidae). Sixteen individuals were tagged (two in captivity and 14 free-living) and an ethogram was generated from acceleration recordings in varying environmental conditions. Two algorithms were used to classify the behaviours of wild fish. Both showed generally similar results during the cold-water season (8-10 degrees C), but differed slightly in the warm-water season (16-18 degrees C). Overall, sea bass were more active during warm season (mean time spent engaged in active behaviours; 46%, range; 24-60%). In contrast, during cold season fish only spent a mean of 29% of their time in active behaviours (range; 15-49%). No clear response to tidal state or ambient light was found, but some fish were more active during the night in the cold water season. Here, we provide the first activity budgets for the conspicuous Argentine sea bass, which contribute to our understanding of rocky-reef fish behaviour in Patagonia.