The enlargement of Cotter Reservoir, Australian Capital Territory (ACT), was completed in 2013 increasing the capacity from 4 GL – 78 GL. This reservoir is home to the nationally endangered Macquarie perch, a medium-sized deep-bodied Percichthyid, native to south-eastern Australia. Previous tracking studies looked at the diel and seasonal movements of this species in the pre-existing reservoir using radio telemetry. This study aimed to look at the seasonal differences in movement using acoustic telemetry in the newly inundated reservoir. A total of 105 adult Macquarie perch were acoustically tagged and tracked from October 2016 to June 2019. The movement metrics characterised were home range, diel range, diel activity and diel mobility. Environmental conditions such as time of day, water temperature, day length and barometric pressure were also investigated in relation to movement of Macquarie perch. This study indicates that adult Macquarie perch have changed their scale of movement based on an increase in available reservoir habitat. This has important implications for access to critical habitat and food resources and is a vital piece of information for management of reservoir bound populations of medium bodied fish.