A fish gathering device (FAD) is an artificial object used to attract fish that live in open ocean areas, such as marlin, tuna, and mahi-mahi. These devices usually include floating buoys or objects attached to the ocean floor. People have used different types of FADs for many years in traditional fishing practices in regions like Island Southeast Asia (especially the Philippines), Japan, and Malta. Today, FADs are also widely used in modern commercial and sport fishing activities.

Fish behaviour

Fish are interested in floating objects, which they use to mark places for mating. They gather around items like floating debris, rafts, jellyfish, and seaweed. These objects help fish see better in open water and provide safe places for young fish to hide from predators. The young fish, however, attract predators. A study in French Polynesia using sonar found large groups of young bigeye tuna and yellowfin tuna closest to the devices, within 10 to 50 meters. A less dense group of larger yellowfin and albacore tuna gathered 50 to 150 meters away. Even further out, up to 500 meters, mature tuna were spread out. The groups varied in size and sometimes overlapped. Other fish also used the FADs, and the groups scattered when it got dark.

Types

Drifting FADs move with ocean currents and are not attached to the sea floor. They can be man-made or natural, such as logs or driftwood. Some drifting FADs have sonar and GPS tools, which allow operators to track them from satellites and monitor fish populations nearby.

Moored FADs stay in one place and are fixed to the sea floor with heavy objects like concrete blocks. A rope made of floating materials, such as polypropylene, connects the FAD to the sea floor and ends with a buoy. The buoy may float on the water’s surface for about 3 to 4 years or remain underwater to avoid dangers like storms and ships. Subsurface FADs last longer, about 5 to 6 years, because they experience less damage. In some cases, the rope above the buoy is made of metal chain. If the buoy becomes loose, the rope sinks to the ocean floor, reducing the risk of hitting passing ships.

Traditional FADs

Fish aggregating devices have been used for many years by fishermen in Island Southeast Asia, Japan, and Malta. These devices are most commonly found in the Philippines, where they are called payao. Payao are long, narrow bamboo rafts that are tied to the ocean floor with rocks. They are usually placed in deep water, but some are also used in shallower areas near the coast. The rafts are about 4 meters (13 feet) long and 1.5 meters (4.9 feet) wide, with one end narrowing. Below the raft, palm leaves from coconut or nipa palms are hung with weights, reaching depths of about 30 meters (98 feet). There are several types of payao, including simple bundles of bamboo, flat rafts with trailing palm fronds (called bonbon), vertical bundles with palm fronds on the top and bottom (called arong), and double-layered rafts with palm fronds both above and below the water.

Modern payao use steel floats shaped like cylinders, bullets, or rectangles, which are stronger in rough seas. These floats are tied to cement anchors placed up to 5,000 meters (16,000 feet) deep. Fish are caught using handline fishing, surface trolling, or small nets called purse seines. Payao are traditionally used to catch fish that swim near the ocean surface, such as tuna, mackerel scad, and kawakawa. These devices can produce up to 200 metric tons of fish. Thousands of payao are placed in groups across the Philippines. Payao have also been introduced to fishermen in Vietnam, Thailand (called sung), Fiji, the Solomon Islands, the Federated States of Micronesia, Papua New Guinea, and other countries in Oceania.

In Indonesia, Malaysia, Timor-Leste, and among the Moken people of Myanmar, a similar method is used and called rumpon or roempon in Malay. This method uses a bamboo raft tied to the ocean floor, with palm leaves or grass bundles attached along its length. Fish attracted to the rumpon are caught using dip nets or encircling nets.

In Japan, fishermen use floating bamboo bundles to attract mahi-mahi, which are then caught with encircling nets. In Malta, a similar method called kannizzati is used to catch mahi-mahi and pilot fish. This method uses flat cork rafts tied to the ocean floor, and fish are caught using encircling nets, long lines, or trolling. Today, kannizzati rafts are often made from polystyrene and have palm fronds from introduced Canary Island date palms (Phoenix canariensis).

Applications

Drifting FADs are common in the Atlantic, Pacific, and Indian Ocean purse seine fisheries. By 2005, they attracted over 1 million tons of tuna (about one-third of the world's total tuna catch) and more than 100,000 tons of other marine animals. The main tuna species targeted by FADs are skipjack (Katsuwonus pelamis), bigeye tuna (Thunnus obesus), and yellowfin tuna (Thunnus albacares). Other animals caught include albacore, dolphin fish, wahoo, blue marlin, striped marlin, mako shark, silky shark, whitetip shark, Galapagos shark, mackerel, and bonito.

Before FADs were used, commercial tuna fishing relied on purse seining to find tuna schools by observing birds and dolphins on the ocean surface. The need for dolphin-safe tuna fishing practices led to the development of FADs. Both recreational and commercial fishing operations use FADs.

Since 1990, the increase in FADs has improved the amount of fish caught by fishing fleets. However, this has caused major negative effects, such as catching smaller fish and a large number of non-target species. This raises concerns about the health of pelagic shark populations.

The U.S. state of Hawaiʻi operates 55 surface FADs near its islands to support sport fishing and marine research.

Blue water FADs can help marine protected areas by keeping fish inside these zones long enough to improve local fish populations. One study found that even a small number of FADs can help increase fish numbers significantly.

Removal

In the Indian Ocean, some nonprofit organizations aim to lessen the harm caused by pollution and damage to coral reefs by removing floating devices that drift onto and harm corals. Oceanika, a United Nations registered nonprofit group, conducts regular missions to remove these devices.