Does fishing on drifting fish aggregation devices endanger the survival of tropical tuna?

Fishermen hold empirical knowledge that tuna aggregate under floating objects, such as lengths of old rope, pieces of wood, or even large marine mammals. There is still no full explanation for this aggregation behaviour, but the past 20 years have seen purse-seine fishery operators take advantage of the associated concentrations of fish. Fishermen cast off floating rafts equipped with buoys which act as FADs.