Fish Aggregating Devices, or FADs, are objects found floating in the ocean, designed or occurring naturally to attract marine life. These can be anything from a simple piece of debris to a sophisticated, purpose-built structure. They create an artificial habitat that draws various species from the open ocean. FADs serve as gathering points for fish and other marine organisms, influencing their distribution in the vast marine environment.
Understanding Fish Aggregating Devices
Fish Aggregating Devices vary greatly in complexity and materials. Simple FADs might consist of natural debris like logs or seaweed. More intentionally deployed FADs often use materials such as bamboo, old fishing nets, ropes, and buoys, often incorporating a subsurface structure. Some modern FADs integrate advanced electronics, including GPS trackers and sonar, to monitor their location and the biomass of fish beneath them.
FADs are categorized into two main types: anchored and drifting. Anchored FADs are fixed to the seabed, remaining in a stationary position. These are typically deployed in coastal areas or shallower offshore waters. Drifting FADs are free-floating and move with ocean currents and winds, often traversing vast distances across the open ocean. Their appearance and size can vary significantly, ranging from small, makeshift rafts to large, elaborate structures several meters in diameter.
How FADs Attract Marine Life
Marine life gathers around FADs for several reasons. One primary attraction is the shelter they offer from predators and strong ocean currents. For smaller fish, the FAD provides a solid object to hide near, reducing their vulnerability in the vast, exposed open ocean. This physical structure also creates a shaded area, appealing to many marine species.
FADs also act as a foundation for a localized food web. Algae and small invertebrates attach to the FAD’s submerged surfaces, initiating a food chain that attracts smaller baitfish. These smaller fish then draw in larger predatory species, creating a concentrated feeding ground. For many pelagic species, FADs serve as navigational aids in an otherwise featureless environment, providing a reference point for schooling and migration. This allows them to conserve energy by congregating rather than expending effort searching for others.
Uses of FADs in Fishing
Fish Aggregating Devices are utilized in both commercial and recreational fishing operations due to their ability to concentrate fish. Commercial fishing fleets, particularly those targeting tuna, rely on FADs to enhance their catch efficiency. Purse-seine nets are often deployed around FADs to encircle and capture large schools of tuna, as well as other species that aggregate beneath them. This method allows vessels to locate and capture fish more quickly than searching the open ocean.
Recreational anglers also employ FADs, though typically on a smaller scale, to improve their chances of success. Sport fishermen might target pelagic species like mahi-mahi, wahoo, or tuna that associate with these floating objects. The use of FADs has a long history, evolving from observations of fish congregating around natural debris to the deliberate deployment of purpose-built structures, increasing the productivity of fishing efforts across various scales.
Impacts on Marine Life and Ecosystems
The widespread use of Fish Aggregating Devices, particularly drifting FADs in commercial fisheries, presents concerns for marine life and ocean ecosystems. One major issue is bycatch, the unintentional capture of non-target species. Large purse-seine nets deployed around FADs often ensnare a diverse array of marine animals, including sharks, sea turtles, marine mammals, and juvenile fish. Many of these bycatch species are released, but often with injuries or high mortality rates.
Another impact is “ghost fishing,” which occurs when abandoned, lost, or discarded FADs continue to drift in the ocean. These derelict FADs, often made of durable materials like plastic and netting, can entangle marine life for years, leading to injury or death. This phenomenon contributes to marine pollution and poses a threat to marine biodiversity. Additionally, FADs can alter local ecosystems if they drift into sensitive habitats, such as coral reefs, where they might introduce non-native species or cause physical damage.
The efficiency of FADs in concentrating fish also contributes to concerns about overfishing. By making fish stocks easier and more predictable to catch, FADs can accelerate the depletion of target species, as well as the non-target species that aggregate with them. To mitigate these impacts, various management efforts are being explored and implemented. These include biodegradable FADs, which break down more quickly in the environment, and FAD tracking systems that allow for better monitoring and recovery of deployed devices. Regulations such as time and area closures for FAD fishing aim to provide temporary protection for vulnerable species and allow fish stocks to recover.