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Improvements in the design of fish-aggregating devices (FADs) could make a major difference in improving the sustainability and efficiency of skipjack tuna fishing in the Pacific Ocean, according to the International Seafood Sustainability Foundation.
The Washington, D.C.-based NGO is pushing for better FAD management and practices, focusing on the skipjack fishery in the Western and Central Pacific Ocean. It asserts that improvements in the design of FADs could help to cut bycatch of overfished bigeye and yellowfin tuna, as well as other species like sharks, dolphinfish, and turtles.
From surveys by the Parties to the Nauru Agreement (PNA) – an organization made up of Pacific Island nations that control a large amount of tuna resources within their exclusive economic zones (EEZ) – as many as 50,000 FADs are likely now in use in the Western and Central Pacific tuna fishery, up from 30,000 just five years ago.
FADs became more popular in the 1990s due to dolphin-free campaigns and regulations. Tuna seiners used to locate tuna by spotting and tracking down dolphins and seabirds feeding on the schools, but in catching the tuna they also netted and killed dolphins. FADs, which can be as simple as a bamboo raft trailing some disused netting, then came into common use. Fish tend to gather around FADs, though the reason for this behavior is not well known.
Some disadvantages of FADs soon became apparent. Many FADs end up abandoned, lost, or discarded, contributing to the problem of plastic litter in the sea. There is also a higher bycatch rate when fishing on FADs, with particular concern about juvenile bycatch of overfished bigeye and yellowfin tuna, as well as sharks, rays, and sea turtles. But two trends are currently transforming the traditional FAD into a more modern, and potentially less environmentally harmful, product.
The first is that attached GPS satellite devices now allow the use of drifting FADs (DFADs). While the cost of the GPS and sonar can be more than JPY 100,000 (USD 1,000, EUR 800) per unit, vessels pay large fees based on the number of fishing days they spend in an EEZ, so they find it profitable to make the most efficient use of their days. Additionally, attaching a sonar device to a DFAD allows fishermen to remotely monitor which ones have attracted a large biomass underneath. A vessel may then focus its effort on the FADs that will yield the most fish for their effort.
As advances in technology greatly increase the number of fish a single seiner may catch, regional fisheries management organizations (RFMOs) such as the Western and Central Pacific Fisheries Commission have been considering strategies to manage their use. Fishing effort is usually managed by vessel days and gear, but the increased use and efficiency of electronic DFADs may now merit their inclusion as regulated gear.
The ISSF has made that recommendation to the WCPFC, along with several others. In some fisheries, supply and support vessels set DFADs, so that fishing vessels can concentrate on catching fish. The ISSF recommends the regulation or banning of setting FADs from support vessels as one way to reduce fishing effort in its report titled “ISSF 2016-11: ISSF Survey Paper on the Treatment of Supply Vessels.”
As DFADs are equipped with transmitters, it should be possible to supply all of the data to fisheries managers to allow them to better understand the number and location of DFADs, better estimate stocks of fish, and to pick up oceanographic data such as water temperature and movement of currents, according to the ISSF.
In addition to better data sharing, the organization is encouraging the WCPFC to mandate non-entangling DFAD design to reduce shark mortality. Most DFADs in the Western and Central Pacific Ocean are made with bamboo rafts trailing large-mesh seine nets –considered to be high entangling-risk FADs. ISSF is promoting an industry-wide conversion to less entangling-risk FADs and non-entangling FADs. The former are made of smaller mesh nets, such as those used for anchovies and sardines, while the latter are made of ropes and canvas, with biodegradable materials preferred to address the plastic waste problem.
This conversion will help reduce mortalities of oceanic whitetip and silky sharks, which are the sharks found most frequently around DFADs. Because these sharks must keep moving to pass water over their gills, when they get caught in the net of a DFAD, they cannot swim and soon die. As the carcasses may subsequently become free and fall off the net, this phenomenon is called “cryptic fishing” bycatch, as it generally isn’t noticed or recorded.
One recommendation the ISSF isn’t making is an outright ban on FADs, as every fishing method has its own problems. Rather, they seek to improve their design and management. The PNA has applied FAD closures in the past order to protect overfished bigeye tuna from being taken as bycatch, but found that overall catches of bigeye did not decline, as fishing effort was refocused to the high seas after the ban went into place in its EEZ.
The ISSF has numerous other recommendations for the WCPFC and other RFMOs overseeing large tuna fisheries, including the use of scientific assessments in setting catch rates and greater observer coverage of the fishing fleet. The current push is on the WCPFC because other RFMOs have already established working groups to consider measures to manage FADs.
“In the WCPO, FAD sets account for about 30 percent of tropical tuna catches. There is a need globally for measures that help better monitor and manage FAD usage in every ocean region,” ISSF President Susan Jackson said. “Shark mortality and other FAD-fishing ecosystem impacts in the WCPO also have to be addressed, for which the wide-scale adoption of non-entangling FAD designs is a critical step.”