Though fishing with fish aggregating devices (FADs, or more generally, floating objects) has been in practice for hundreds of years, the amount of FADs being used by purse seine vessels has increased steadily in the last two decades. In 2019, the last year for which we have complete data, FAD sets accounted for 38% of the more than 5 million tonnes of tropical tunas (bigeye, skipjack and yellowfin tuna) caught globally. For skipjack tuna, FAD sets accounted for 46% of the 3.2 million tonnes caught. Clearly, fishing on FADs is a crucial means of providing an important food source for the world.
Indeed, fishing on FADs is efficient and widely used. But the use of FADs also comes with downsides that are of concern and must be addressed. I would like to share with you some of the work that we at ISSF have been doing — together with our research, NGO, and industry partners — to ensure that these fisheries are sustainable for the long term.
One of the main concerns about FADs has long been that sets on floating objects have higher rates of bycatch of non-tuna species than sets on free-swimming schools. Many claims related to this have been campaigns that are not rooted in science. One of our earliest areas of work on FADs, therefore, was analyzing independent observer data to accurately document bycatch in purse seine fisheries. It turned out that bycatch rates on FAD sets (2.24%) are indeed higher than in free school sets (0.43%), but much of it is of species that are actually utilized such as mahi-mahi and the minor tuna species. Also, this rate is small compared to the bycatch of other tuna fishing gears such as longlines and gillnets.
In fact, what really matters in addressing the bycatch in FAD fisheries is not so much identifying a particular number, but rather identifying and focusing on those bycaught species that are of conservation concern. Because of their low reproductive rates and other life history characteristics, silky sharks — which are often caught in FAD sets (they are caught on free school sets, too, but less often) — are a vulnerable species.
We have therefore identified ways in which silky shark bycatch can be mitigated, and many fleets have adopted some of these practices voluntarily. In addition, regional fisheries management organizations (RFMOs) in the Pacific and Indian Oceans have adopted best practice guidelines for the safe release of sharks and rays.
Of similar concern is the entanglement of silky sharks and other wildlife in the netting used as hanging structures in traditional FADs. This is a phenomenon known as “ghost fishing,” and it was first identified by ISSF-supported marine scientists in 2013. Thanks in part to ISSF advocacy efforts and those of partner organizations, tuna RFMOs now require FADs to be either completely non-entangling or of low risk of entanglement. This issue was identified and addressed in the span of three to six years, an encouraging sign of progress and political will.
A large proportion of the yellowfin and bigeye tuna caught on FADs is immature. Many people assume catching immature fish or “juveniles” results in overfishing, but this is not necessarily the case. A fish stock can be overfished by catching too many juveniles, by catching too many adults, or by catching too many of both. In terms of overfishing, what matters is how fishing affects the reproductive potential of the stock. Catching adults affects today’s reproductive potential, while catching juveniles affects it sometime into the future.
A different impact from catching juvenile yellowfin and bigeye tunas is that the maximum catches that can be sustained — the so-called Maximum Sustainable Yield, or MSY — is lower than if fishing is selectively shifted towards larger individuals. This is not a biological impact in the sense of overfishing. It is an issue for fishery managers to address in terms of allocation between fishing gears. RFMOs need to define management objectives and adopt harvest strategies that will achieve those objectives.
Many of the FADs that are deployed each year are lost or abandoned and some end up in vulnerable habitats such as coral reefs. In addition, when FADs are made with plastic materials such as old netting, these losses add to marine debris as FAD decay.
ISSF scientists have conducted at-sea research, as well as consultations with fishers through workshops, to identify ways in which these impacts can be mitigated. A major part of this work is focused on how to transition to FADs made mostly or completely of biodegradable materials. As of today, biodegradable FAD trials are being conducted in all oceans, and we are confident that a viable FAD that is fully biodegradable (except for the buoy and flotation) will be identified soon.
Another aspect of mitigating these impacts is preventing the loss or abandonment of FADs and incentivizing their recovery. While some RFMOs are encouraging or adopting FAD recovery targets, these targets are likely insufficient. One of the problems is that there are no clear rules of FAD ownership and responsibilities, with weak controls regarding accountability. As a result, FADs deployed by a given vessel may be appropriated by other vessels that encounter them. RFMOs must address this issue by adopting clear rules of ownership and responsibilities.
ISSF has identified six elements that are of utmost importance for FAD management:
ISSF also adopted a conservation measure on FAD management. The measure requires ISSF participating companies to conduct transactions only with those purse seine vessels whose owners develop and make public FAD management policies that explain how their vessels are addressing the six elements above. The aim is that this increased transparency into vessel practices will spur RFMOs to continue improving FAD management.
As mentioned at the opening of this article, the use of FADs is responsible for an important portion of the world’s tuna catch. Without FADs, the level of tuna catch would be significantly reduced, even for those species like skipjack tuna, the stocks of which are at healthy levels of abundance worldwide. Global food security would surely suffer as a result.
And a wholesale shift to an alternative, FAD-free method — which would be necessary to meet global demand for a protein-rich food source like tuna — is not without concern. Because no fishing method is without environmental impact, a decrease in fishing on FADs and the corresponding increase in fishing via other methods would only serve to increase the impact of the non-FAD method. For example, as FAD fishing effort shifts to free school sets, pressure on adult stocks of yellowfin tuna increases — a problem for a species that is currently overfished or close to being overfished in some oceans.
Finally, FADs also present a unique opportunity to improve our understanding of the pelagic ecosystem. All FADs are equipped with GPS tracking systems. Many FADs have sophisticated echosounders that measure the biomass of tunas aggregated underneath. As this information is increasingly made available voluntarily by many fleets to marine scientists, we are learning more about tuna behavior and improving tuna stock assessments. It is important that these data contributions to RFMOs become the norm in order to make such analyses routine.
RFMOs have made progress on FAD management over the last 10+ years. Ten years ago, for example, the only controls in place were time/area prohibitions on FAD use in some oceans. Today, all RFMOs have some management system in place for tropical tuna fisheries that includes several essential elements of FAD management like data reporting on FAD fishing and activities; seasonal closures; FAD limits; 100% observer coverage; and the safe release of sharks and rays. And as discussed, the way RFMOs worked to adopt non-entangling FAD requirements in response to “ghost fishing” reveals that fisheries managers can be moved when research findings and political will converge.
We look forward to RFMOs persisting in this vein: they must progress FAD management measures while also ensuring that current FAD requirements are being followed. All RFMOs have a compliance process, and this process must address FAD management requirements.
We still have work to do toward improving the use of FADs while ensuring that there are plenty of fish in the sea. But we’ve made substantial progress to date. ISSF and likeminded organizations will continue to work toward achievable, science-based solutions for reducing the impact of FAD fishing on global tuna fisheries and the broader marine ecosystem.