This paper uses an index number profit decomposition approach to examine recent drivers of change in profitability in two key Commonwealth prawn fisheries, the Northern Prawn Fishery and the Torres Strait Prawn Fishery. This approach allows for the drivers of profitability that can be influenced by a fishery manager (fish stocks and productivity) to be separated from those that cannot (output prices and input prices). The results reveal that a divergence in the economic performance of the two fisheries has been the result of differences in productivity trends. These differences are the likely result of differences in fishery management arrangements between the two fisheries.