Environmental drivers of yellowtail kingfish, Seriola lalandi, activity inferred through a continental acoustic tracking network

1. Identifying the species response to changing environments can contribute towards proactive and adaptable resource management and, although obtaining observations can be logistically challenging for aquatic species, can be postulated through monitoring.2. A network of acoustic tracking receivers (n = 93) across south-eastern Australia was used to identify the effects of environmental conditions on the activity of the yellowtail kingfish (Seriola lalandi, n = 63), an economically important species with a crucial role in pelagic ecosystems. Activity (measured via tri-axial acceleration) provides an insight into the energetic expenditure of animals, which is linked to movement, behaviour, and physiological processes.3. Kingfish activity was strongly influenced by sea surface temperature and hour of day, with smaller effects from distance to nearest landmass and bathymetry. Activity also decreased during higher tides and periods of greater moon fraction. Findings show that the energetic responses of kingfish are sensitive to long- and short-term changes, which can regulate behaviours and physiological processes. Changes in kingfish activity and movement (residency and space use) were further investigated at a seasonal aggregation in a small temperate estuary (approx. 120 km(2); Coffin Bay, South Australia), where individuals remained during the austral spring and summer (September-April), with a complete exodus in winter. Fifty per cent of tagged fish returned to this estuary in three consecutive years, indicating its importance for aggregating kingfish.4. While residing in Coffin Bay, kingfish activity varied between interconnected areas, with temperature, hour of day, tide height, and moon fraction again identified as important explanatory variables. These findings have implications for the energetic budgets of large pelagic fish in subtropical and temperate regions, which are facing rapidly changing climates.5. These results are important for understanding and accounting for the potential responses and physiological impacts of future climatic conditions on migratory pelagic species.