PNA data offers a better understanding of drifting FADs

In recent years, concern has been growing about bycatch of juvenile bigeye tuna by purse-seiners setting nets on drifting fish aggregation devices (dFADs). The main target of the purse-seiners is the more plentiful skipjack tuna, but as bigeye inhabit the same tropical seas, they are often taken as well.

The devices typically consist of a raft or buoy trailing a length of disused netting tied into the shape of a string of sausages, used to attract tuna – which like to gather under floating objects. Modern dFADs are equipped with a solar-powered GPS device and a fish finder to report their location and the amount of fish gathered under them. Support vessels manage the deployment and retrieval of the dFADs, so that fishing vessels can concentrate on fishing. 

In the Pacific, the Western and Central Pacific Fisheries Commission (WCPFC) enacted closure periods for dFAD deployment, but after receiving some encouraging data on bigeye stocks last year, the commission raised catch limits and reduced the closure periods. Still, the WCPFC has called for further study of dFADs and their interactions with fish and the environment. But until recently, dFADs were exclusively monitored by fishing companies without real-time data-sharing with regulatory bodies, making any extensive study on dFADs difficult.

However, the authors of a recent report in the journal Scientific Reports titled “Environmental versus operational drivers of drifting fish aggregation devices (dFADs) beaching in the Western and Central Pacific Ocean,” were given access to data provided by the Parties to the Nauru Agreement (PNA) that allowed them to simulate the dispersal and movement of dFADs, taking deployment sites and ocean currents into account.

The data-sharing has led to a much better understanding of how dFADs interact with the natural environment, according to Lauriane Escalle, the lead author of the dFAD report. She and her co-authors estimated that between 30,000 and 65,000 dFADs are deployed annually in the Western and Central Pacific Ocean. Due to the counter-clockwise flow of the South Equatorial Current, dFADs are deployed near islands in the east and allowed to drift west across the fishing grounds. Equatorial countries such as Kiribati have many FADs moving through their waters, so a significant number wash up on its shores where they may drag on coral beds, causing damage. If dFADs are not retrieved, they often end up beaching or entangled in coral to the west on Tuvalu, on the northeast shore of Papua New Guinea, or the neighboring Solomon Islands.

Since the currents are largely responsible carrying dFADs to this area, changing deployment locations would have little effect. The authors instead suggest management approaches combining dFAD deployment limits, the use of biodegradable dFADs, recoveries at-sea close to sensitive areas, and removal of beached dFADs.

The PNA is a group of Pacific island nations that jointly manage tuna resources. They have instituted their own controls on dFADs and also operate a Vessel Day Scheme under which fishing vessels pay based on the number of days they operate in the exclusive economic zones of the members. To manage these in real-time and across national boundaries, the PNA has introduced a data-sharing platform that includes tracking and monitoring of dFADs called the Integrated Fisheries Information Management System (iFIMS).

The system was initially developed for Papua New Guinea’s National Fisheries Authority (NFA). It now contains sections for data for the NFA, PNA, the fishing industry, and flag states of the fishing fleets.

Escalle said that while PNA data was used, it was not accessed through the new platform.

“We are using data from the PNA FAD tracking program, but through a SPC/PNA collaboration, we directly receive the data on a daily basis, with a two-month delay, and have a copy of the database,” Escalle told SeafoodSource.

In future studies, real-time data may be available. But the platform is not limited to data on dFADs. Through its 16 management portals, it also offers many other functions. For example, it allows patrol boats on surveillance missions at sea to check vessel licenses online. Papua New Guinea’s NFA can share import/export data related to fisheries with the government’s Customs Department, and it can share catch data with the Pacific Community (SPC) for stock assessments. The PNA can access data and reporting needed to manage purse seine fishing in PNA waters under its Vessel Day Scheme. And data can be managed for verification of chain-of-custody of fish needed for Marine Stewardship Council certification of its skipjack and yellowfin purse-seine-free fishery.

This is part of a general trend toward real-time electronic monitoring and reporting in the fishing industry. Scientists and fisheries managers will have much better data to work with in future. The downside from the fishermen’s point of view is that their formerly private information, such as favorite fishing locations, must be shared.

Photo courtesy of Shutterstock


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