The science of sustainable seafood, explained

John West Accused of Breaking Sustainable Tuna Pledge

John West, a seafood cannery known for its tuna products in the UK, is under scrutiny by Greenpeace UK for catching 98% of its tuna with Fish Aggregating Devices (FADs).  FAD purse seine tuna fishing is considered unsustainable by organizations like Greenpeace and Monterrey Bay Aquarium because of the, “indiscriminate killing of marine life,” due to the bycatch associated with this gear type.

Exacerbating the problem is John West’s commitment to 100% sustainability by the year 2016, a promise made in 2011. Ariana Densham believes the use of FADs is, “undermining the world-leading standard set by UK supermarkets,” and suggests John West will fail to keep its word by next year. She calls for consumers to avoid John West tuna products altogether.

Comment by Laurent Dagorn and Gala Moreno

While FADs certainly have their benefits for purse seine tuna fishing, their impact on tuna stocks and the broader marine ecosystem has increasingly come into question – specifically regarding the bycatch of non-target species. FAD´s are usually viewed as fishing tools with detrimental impacts on the ecosystem because they kill other marine wildlife. However this fact is inherent to any fishing gear. Fishing impacts the ecosystem, no matter which fishing gear is used. Therefore, the important issues with FADs are 1) quantifying, with scientific data, how big that impact actually is, 2) determining if the impact is acceptable for the amount and diversity of fish caught, 3) comparing it with the impact of other fishing gears, and 4) implementing measures to reduce an impact if it is too high for the ecosystem, taking into account all fishing impacts.

A recent paper, Is It Good or Bad to Fish with FADs? What are the Real Impacts of the Use of Drifting FADs on Pelagic Marine Ecosystems?, which was peer-reviewed and published by the journal Fish and Fisheries, presents some useful findings that dive into three important topics: tuna stocks, bycatch of non-target species and ecosystem impact.

Impact of FADs on Tuna Stocks

Although FADs appear to have no more substantial impact on tuna stocks than other fishing methods, as all components of fishing upon a stock contribute to overfishing, there is a real concern for overfished tuna species caught at FADs, as well as for the catch of undersized (not juveniles) tunas.

Ongoing research to find solutions

  • Acoustic discrimination of tuna species at FADs, so that those FADs with overfished or undersized tuna species are avoided by fleets.
  • Tuna behavior prior to setting and within the net to design escape windows for overfished species or undersized tuna i.e., bigeye tuna
  • Shallower FAD structures to examine if they don’t attract bigeye tuna

Catch of Juveniles

Sustainability of tunas and pelagic ecosystem is achieved by reducing the overall impact of all fishing gears as each harvesting strategy has its specific effects on the ecosystem. As an example, many people express concern that the catch of juvenile bigeye on floating object sets is very high. Over 65% of the bigeye catch in FAD sets, in weight, consists of immature individuals. The catch rate of juvenile bigeye in pole-and-line fisheries is even higher, 100%. In contrast, the catch in weight of juvenile bigeye in longline fisheries is only 2%-8%. But, the catch of juveniles is not necessarily unsustainable. The fact is that a fish stock can become overfished by taking too many juveniles, by taking too many adults, or by taking too many of both. To put it another way, it is bad to catch too many of tomorrow’s spawners, but it is also bad to take too many of today’s spawners. In the western Pacific, where bigeye has been subject to overfishing, the impact of longline and purse seine fisheries on spawning biomass is very similar in magnitude. The RFMOs need to manage all sources of fishing mortality on the stock, not only those that catch juveniles.

Bycatch of Non-Target Species

On average, bycatch (species other than skipjack, yellowfin and bigeye tuna) represents between 1.7 and 8.9% of a purse seine vessel’s catch, depending on the ocean, and consists primarily of other bony fish and sharks. Credible data on the full composition of bycatch globally is difficult to obtain because observers onboard collect them and therefore depend on observer coverage and their specific focus, which varies by ocean. While improved data collection is essential, current estimates reveal important details regarding bycatch of non-target species. So, although current data and research do not indicate that FADs are inherently bad, all types of fishing sets require active management, which is only possible through improved understanding of FADs and their use. Work to achieve this improved understanding – ISSF’s bycatch research cruises – have led to the development of innovations such as the non-entangling FAD design. With ISSF support, scientists are also testing net release panels for non-target species, which could further minimize bycatch. Because the issues here are complicated, and the biology impacted is varied, the impact of FADs on different species is broken down below:


·     The shark bycatch-to-tuna catch ratio in purse seine fisheries is quite small, on average, less than 0.5% in weight. However, the global magnitude of catch of the purse seine fishery is quite large, so reducing the mortality caused by these fisheries can contribute towards global conservation efforts.


·     Whale shark interaction rates with tuna purse seine gear are very low and these interactions do not occur in FAD sets.


·     Rays are an uncommon catch in tuna purse seine gear, generally less than 0.1% by weight, and again do not occur in FAD sets.

·     Sea turtles are caught in very small numbers ­– from a few tens up to a couple of hundreds of individuals per year in every ocean – by purse seiners. Most of them (> 90%) are released alive relatively easily and any FAD entanglement can be eliminated with the use of non-entangling FADs.


·     A large (80% to 95%) portion of the catch of non-target tunas in FAD sets is minor tuna species and other bony fishes. In some cases, these are eaten by the crew. In other cases, local markets have developed to commercialize these fish. But, in most cases, they end up being discarded at sea, which is a wasteful practice that undermines the FAO Code of Conduct for Responsible Fisheries. Retention and creation of a market for this catch should be encouraged.



       Ongoing research to find solutions

  • For sharks: Testing escape windows to release them from the net
  • For sharks, bony-fish and tunas: Testing species spatial and social behavior when splitting one FAD in two (potential species segregation and hence catching less by-catch in one of the FADs).
  • For sharks and bony-fish: encircling them before the set or inside the purse seine net to release them outside the net.

 Proposed solutions

  • To reduce turtle bycatch: do not cover FAD surfaces with mesh (see guide for non entangling FADs)
  • To reduce shark entanglement: Use non-meshed materials such as ropes or canvas sheets for hanging components (see guide for non entangling FADs)
  • To reduce sharks, turtles, rays and whale sharks by-catch: Best practices to release by-catch from purse seiners.
  • To reduce bycatch with little impact on total target catch: avoid setting on small tuna schools at FADs

All types of fishing gears require active monitoring and management and FADs are no exception. ISSF strongly supports several initiatives such as greater data reporting, since our understanding of FAD usage and its impacts (e.g. bycatch) depend on more and better data. We support improvement of data, on a global scale, collected by observers and vessel operators, to accompany science-based FAD management advice.


Additional Resources

Dr. Laurent Dagorn
A French senior scientist working for the Institut de Recherche pour le Développement (IRD, France), Laurent Dagorn, PhD, has published more than 100 scientific papers, of which more than 60 were in peer-reviewed international journals. His main research interest concerns the ecosystem approach in tuna fisheries, from the investigation of the behavioural ecology of tropical pelagic fish associated with floating objects (e.g. fish aggregating devices – FADs) to the development of mitigation techniques. He has spent about 15 years in the Pacific (French Polynesia, Hawaii, California) and Indian (Seychelles, La Réunion) oceans, collaborating with various scientific organisations and tuna RFMOs. Laurent Dagorn has been the coordinator of a FP5 European Union project (FADIO) on the behaviour of fish at drifting FADs in 2006, and of a FP7 EU funded project (MADE) dealing with the mitigation of adverse ecological impacts of open ocean fisheries (tuna purse seiners and longliners). He has supervised 10 PhD students from 7 different countries. Since 2015, he is the head of the research lab MARBEC (Marine Biodiversity, Exploitation and Conservation) gathering more than 200 scientists from the French research institutions IRD, Ifremer, CNRS and University of Montpellier, located in the South of France (Sète, Montpellier, Palavas) and in the tropics. He is a member of the Scientific Advisory Committee of the International Seafood Sustainability Foundation (ISSF) and chairs the Bycatch Committee of this foundation, and he is also a member of the Scientific and Technical Advisory Committee of the International Pole and Line Foundation (IPNLF).
Dr. Gala Moreno
With a doctoral degree in tuna behavior around Fish Aggregating Devices (FADs), her research is mainly focused on understanding the effects of FADs on tunas and pelagic ecosystem and finding solutions to reduce adverse impacts of FADs. She has spent 16 years, working with purse seine fishers from Indian, Atlantic and Pacific Oceans to gather their knowledge on tuna behaviour and understand their strategy working with FADs. She worked in AZTI Tecnalia as senior researcher in Fishing technology and Tuna research areas, where she was coordinating within AZTI, GAP2 a European project on the value of stakeholder driven science within the context of fisheries’ governance, MADE a European research project devoted to mitigate the impacts of FADs on pelagic ecosystem and FADIO European project on tuna behavior around FADs. Gala has been head on numerous research projects related predominantly to tuna behavior and technology associated with fishing and fisheries management. She is currently research associate in ISSF, member of the by-catch steering committee of ISSF since 2010 as well as member of Fisheries Acoustic Science and Technology (FAST) working group of ICES since 2005. A frequent invited presenter at conferences and published on topics including tuna behavior, FADs and Local ecological knowledge. Gala has taught university-level courses on FADs, eco-ethology of pelagic species and hydro acoustics for pelagic species monitoring in the University of Basque country and Instituto Español de Oceanografía.

Share this story:


Subscribe to our newsletter:

Read more:

One Response

  1. Useful reading. Thank you!

    Two shark-related questions/comments:

    Laurent, wondering about your Filmalter et al 2013 paper? FAD ghostfishing of sharks could be a major component of its bycatch, no? (And one with a relatively straightforward solution.)

    In addition to percentages, could you provide estimates of total weight of bycatch by the gears you mention. You allude to the fact that the sheer size of the PS fishery means that even though bycatch rates are low, total amount could still be high. How high? More or less than caught by longliners? If you split FAD and free-school shark bycatch, is that a difference worth noting? (Or maybe the quality of the LL v PS shark bycatch – is one fishery more likely to catch more vulnerable species than the other?) Just trying to place in the context of the various tuna fisheries. Thanks again.

Leave a Reply

Ray Hilborn's every-so-often newsletter

The best way to keep up with our stories.