Illegal, unreported and unregulated fishing (IUU) is an issue around the world. Fishing industry observers believe IUU occurs in most fisheries, and accounts for up to 30% of total catches in some important fisheries.

Illegal fishing takes place when vessels or harvesters operate in violation of the laws of a fishery. This can apply to fisheries that are under the jurisdiction of a coastal state or to high seas fisheries regulated by regional fisheries management organisations (RFMO). According to the UN Food and Agriculture Organization (FAO), Fisheries and Aquaculture Department, illegal fishing has caused losses estimated at US$23 billion per year.

Unreported fishing is fishing that has been unreported or misreported to the relevant national authority or RFMO, in contravention of applicable laws and regulations.

Unregulated fishing generally refers to fishing by vessels without nationality, vessels flying the flag of a country not party to the RFMO governing that fishing area or species on the high seas, or harvesting in unregulated areas.

The drivers behind illegal, unreported and unregulated (IUU) fishing are similar to those behind many other types of international environmental crime: pirate fishers have a strong economic incentive – many species of fish, particularly those that have been over-exploited and are thus in short supply, are of high financial value.

Such IUU activity may then show a high chance of success – i.e. a high rate of return – from the failure of governments to regulate adequately (e.g. inadequate coverage of international agreements), or to enforce national or international laws (e.g. because of lack of capacity, or poor levels of governance). A particular driver behind IUU fishing is the failure of a number of flag states to exercise effective regulation over ships on their registers – which in turn creates an incentive for ships to register under these flags of convenience.

Since no one reports catches made by pirates, their level of fishing cannot be accurately quantified.