For centuries, fishermen have known that tuna and other species form large schools under floating objects, whether natural or man-made. Industrial tuna fishing crews utilize this knowledge to construct specialized fish aggregating devices, or FADs, which make it easier to find and catch fish.
Recent advances in technology allow fleet owners to track their FADs and even estimate the amount of tuna beneath them using sonar, transmitting the location and numbers back to their home office by satellite. These advances have come at a price. While using FADs dramatically increases fishing efficiency, it also raises the risk of overfishing an already- dwindling tuna population, as reflected in the record haul of tuna caught in association with floating objects in recent years.
The Western and Central Pacific Fisheries Commission (WCPFC)—an international body composed of governments with fishing interests in the western and central Pacific Ocean—will hold its annual meeting Dec. 1–5, 2014, in Apia, Samoa. The Pew Charitable Trusts is calling on Commission members to take a science-based, precautionary approach to managing the tuna fishing industry’s use of FADs, which also put at risk other valuable and vulnerable species, including sharks and sea turtles.
Bigeye’s big problem
The western and central Pacific is home to the world’s largest skipjack tuna fishery. A majority of this catch is made in association with FADs. According to an analysis by the Commission’s Scientific Committee, one-third of the tuna populations under its management are overfished and in need of rebuilding. In 2013, fishing vessels landed 1.8 million metric tons of skipjack, the most commonly caught tuna species, and more than 82,000 metric tons of bigeye tuna, both records. In fact, overfishing of bigeye has continued for so many years that this population is at only 16 per cent of its unfished size.
The unmanaged proliferation of FADs is a major driver of bigeye overfishing. Juvenile fish, those too young to reproduce, regularly aggregate with skipjack and other species that form large schools around floating objects. Vessels using fish aggregating devices land 90 per cent of the bigeye caught in the region even though their intended catch is skipjack.
Trouble for sharks
Worldwide, about 100 million sharks are caught and killed in fisheries each year. Large-scale, industrial fishing has depleted several species that live in the open ocean, including silky, blue, and oceanic white-tip sharks. These top predators are known to congregate around FADs, and hundreds of thousands get caught up in nets along with tuna. Sharks are also particularly vulnerable to getting caught by fishing vessels that use wire leaders and shark lines. Without an improvement in management, vulnerable sharks will continue to experience unsustainable pressure.
Scientists report that more-effective management of FAD use is essential to rebuilding the bigeye tuna population and to reducing shark mortality. Taking steps to improve oversight of this fishing gear would also lead to increased transparency and accountability for vessels operating in the western and central Pacific.
To help western Pacific bigeye recover from overfishing, scientists have called for purse seine vessels, which use large nets to catch fish, to make a 36 per cent cut in the number of times they put their nets in the water around a FAD. This reduction would likely allow many more juvenile bigeye to mature and ultimately reproduce, helping the population to recover. This would also reduce the number of silky, oceanic white-tip, and blue sharks caught incidentally by these vessels, a result known as by-catch.
A second way to manage fish aggregating devices is by simply capping the number of vessels that rely on them, or by limiting the number of floating objects that a vessel can deploy. In 2013, a record 297 boats fished for tuna in the Commission’s management area using purse seine gear, and most of these relied on FADs to locate fish. This year, early reports indicate that the number continues to grow, with approximately 305 vessels expected to target tuna in the area.
The WCPFC was established in 2004 through a treaty based on relatively modern principles of fisheries management and the objective of ensuring the long-term conservation and sustainable use of highly migratory fish stocks in the western and central Pacific Ocean. But 10 years later, the bigeye tuna population continues to be overfished and several shark populations remain vulnerable and threatened. If nations follow a precautionary, science-based approach to adopting conservation and management measures this December it would begin to restore some balance to the region’s fragile marine ecosystems.