Can fishing vessels turn off their AIS?

Fishing vessels can turn off their AIS – and Global Fishing Watch can help detect when this appears to occur. We can also flag instances where ships disappear or appear suddenly, jump thousands of miles at once, or appear to fish on land. AIS was primarily designed as a safety mechanism to help avoid collisions at sea, so turning off AIS can put a vessel and its crew at risk of being hit by another ship.