Background: Understanding the movement behaviour of flow-dependent fish species is one of the foundational principles underpinning the effective management of highly modified riverscapes. Aim/Methods: To determine how variations in river discharge and instream barriers affect the residency, survival and movement of golden perch (Macquaria ambigua) in the degraded Gwydir River system within the northern Murray–Darling Basin, we monitored the movement of 25 acoustic-tagged golden perch for 3 years using a linear array spanning ~180 km of the systems lower reaches. Results: Golden perch were largely sedentary for extended periods, with movements constrained by the barrier maze that now defines the Gwydir system. High flows facilitated passage over instream barriers, with the highest periods of activity occurring in spring and early summer. Our findings are indicative of the behaviour of a highly constrained and isolated population of golden perch that is now likely to be neither a source nor a sink. We propose that the population could now be considered a false sink, perpetuated by re-stocking of hatchery reared fingerlings. Conclusion: To rehabilitate the golden perch population in the Gwydir and in other systems’ in similarly poor condition throughout the Murray–Darling Basin, will require major institutional and societal change.