As the name suggests, they help fishermen catch more fish. A FAD is essentially flotsam (something floating out at sea). It is seemingly still unknown as to why fish choose to congregate around flotsam but they sure like doing so. Perhaps there is something appealing in flotsam whilst for miles and miles in every direction there is nothing but open sea.
The fisherman in most parts of the world are using these devices and the type of device can vary depending on which sea it is in, whether it is close to land or if it’s far out at sea. Whilst local small sized fisheries build simple homemade devices which anchor to the seabed, the larger commercial fishing fleets will set up multiple floating smart FADs and they will attach sonar and GPS in order to track their position and the amount of fish in the vicinity.
FADs make the lives in fishermen a lot easier, however, they can have an adverse reaction on the ecosystem by catching fish that have not yet gone through one reproduction cycle, as well as bycatch of turtles and other species which often don’t survive once being chucked back into the sea.
Having said that it’s important to note that FADs have advantages. In the Pacific where overfishing of the reefs are causing damage to the reef ecosystem, shifting to Tuna fishing through FADs protects this environment. This is perhaps why many nations in the Pacific are promoting and sharing information on how to build moored FADs which can be built to last.