The effects of six common forms of fisheries support are estimated using a bioeconomic model of the global fishery. The results show that all have the potential to provoke overfishing, to lead to fish stocks being overfished, to encourage illegal, unreported or unregulated (IUU) fishing and to increase fleet capacity, but that their effects can vary significantly both in scale and how they are distributed at the fleet level. The fisheries management system can mitigate, though not entirely eliminate, these impacts. Supports based on reducing the cost of inputs purchased by fishers provoke the greatest increase in fishing effort, with associated risks of overfishing. This includes fuel subsidies, which are also shown to deliver less than 10% of their value in actual benefits to fishers in some cases, making them the least effective means of transferring income to fishers of those evaluated. Payments based on improving fishers' business operations provided the greatest benefit to fishers and had relatively less tendency to increase fishing effort. If only USD 5 billion in fuel support was converted into support of this type, fishers would see increased income of more than USD 2 billion, while at the same time reducing effort and improving fish stocks. Such a change would also provide relatively more benefit to smaller fishers.