IUU fishing is an activity driven by economic factors, that is, the IUU fisher's expected net benefit. When expected net benefit is positive, the activity will continue somewhere, somehow. This underscores the importance of co-operation, international and regional, to ensure that the expected benefits from IUU activities are reduced by making sure potential loopholes are identified and fixed.OECD work on IUU fishing activities focuses on identifying new strategies that are based on the economics of the IUU activity. A number of key economic, institutional and social drivers have been identified, including excess fishing capacity, market value (price) of fish, the level of MCS (including VMS) operations and associated sanctions against IUU fishing, domestic management regimes, weak international legal frameworks and poor economic and social conditions in many parts of the fisheries world. These economic, institutional and social drivers underpin or weaken the profitability of IUU activities.In devising new strategies and measures to combat IUU fishing, it is essential to identify instruments that either reduce the expected income stream or alternatively increase the costs of the activity. To change the "expected benefit" of IUU fishing operations a number of actions can be taken. Among the promising avenues are efforts to step up monitoring and surveillance of IUU fishing activities. However, to be effective these also require that sufficiently restrictive levels of fines and penalties are in place. In the longer term, emphasis is also needed on more general development and educational activities that can provide fishers with alternative sources of income.