A recent Pew report documented the growing and largely unmanaged proliferation of drifting fish aggregating devices (FADs) in the world’s oceans. By our conservative estimate, over 120,000 FADs are dropped into tropical waters every year by the purse seine tuna fishing industry. Tuna gather under the floating devices and then are caught in large nets set by fishing vessels.
But most FADs are never recovered from the ocean. They continue to fish, becoming what’s called ghost fishing gear or marine debris, and are left to sink or wash ashore, sometimes in sensitive coastal habitats such as coral reefs. FADs made of old fishing nets are notorious for entangling nontargeted species, including turtles, sharks, and other marine life. Increasingly sophisticated technologies allow fishermen to determine how much tuna has gathered under some FADs—and whether they are worth returning to at all.
FADs are used widely in every ocean region, particularly by vessels flagged to the United States and the European Union. The evidence shows that the uncontrolled increase in FAD use over the past 20 years in skipjack fisheries worldwide has harmed other tunas— including bigeye—as well as sharks, sea turtles, and other marine animals. Fisheries scientists agree that the significant increase in FAD use has contributed to the overfishing of bigeye tuna in the Atlantic and Pacific oceans.
Fishery managers increasingly recognize that greater regulation of FADs is needed to ensure that their use does not harm tuna stocks, nontarget species, or ecosystems as a whole. Still, the international bodies responsible for management of tuna fisheries have been slow to respond.
So far, regulators have taken only small steps toward managing FADs, such as requiring vessels to use devices that are biodegradable and designed to reduce the risk of entangling nontarget marine life such as sharks. These attempts to combat marine debris, limit ghost fishing, and reduce unintended catch represent positive steps. However, none of these policies addresses the fundamental problem of unmanaged FAD use: the overfishing of tunas. Without policies designed to reduce the capture of bigeye around FADs, too many of these fish—almost all too young to reproduce—will continue to be caught, removed, and eaten.
Bigeye tuna management options that could address overfishing have one common factor: They encourage—or better yet, require—industry to catch fewer immature fish. Managers could design FAD-fishing closures of sufficient duration and size to reduce fishing around FADs; limit fishing in potential bigeye “hot spots” where that species is known to aggregate in larger numbers; restrict fishing on schools of tunas gathered under floating objects; or simply cap the number of juveniles that can be legally caught.
Implementation of one or more of these policies could put bigeye tuna in the Atlantic and Pacific oceans on a path toward recovery.
Amanda Nickson directs Pew’s global tuna conservation efforts.