In the field of restoration ecology, understanding, and indeed measuring, links between management interventions and target environmental outcomes is much debated. For aquatic systems, fish are often used to justify investment in restoration, such as watering, invasive species control, or habitat rehabilitation. However measuring the drivers of change in inherently complex systems, following management interventions, at population scale, is problematic. Here we provide an example of a well-designed, long term experiment, measuring population scale response of fish to a large intervention. Between 2005 and 2008, 4500 pieces of structural woody habitat (SWH) were restored in a reach of the Murray River, and a 7 year monitoring program implemented. We hypothesised that the size of the fish population in this study reach would increase in comparison to reference reaches, through increases in immigration and survival, and decreases in emigration. In particular, while previous programs have shown that native fish use re-introduced SWH, there have been few studies undertaken which show this use is directly related to an increase in population size, rather than a redistribution of fish already present (ie a ‘honeypot’ effect). Our presentation will discuss final results of this seven year experiment, and show a significant increase in population size for Murray cod following the intervention. We present a multiple lines of evidence approach to define fish population change in response to the management intervention. The monitoring approach used here can be applied to monitor outcomes of many management interventions, including provision of environmental water or fish stocking.