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Drifting fish aggregating devices (dFADs) are human‐made floating objects widely used by tropical tuna purse seine (PS) fisheries to increase catch of target species. However, dFAD use has several negative impacts, including increased potential for overfishing, higher juvenile tuna catch, higher bycatch compared to other PS fishing modes, ghost‐fishing, and generation of marine litter. Based on these impacts, some stakeholders, especially environmental non‐governmental organizations and other competing fishing industries, suggest that dFADs should be completely banned. We list the pros and cons of dFAD fishing; address how to improve current management; and suggest solutions for the sustainability of dFAD fishing in the long term. A dFAD ban would lead to major changes in the availability and sourcing of tuna for human consumption and decrease the licensing revenue received by many developing states. Most importantly, we argue that tools exist today to manage for, reduce or eliminate most of the negative impacts of dFADs (e.g., bans on discards, limits on active dFADs, biodegradable non‐entangling constructions, time‐area deployment closures, recovery programs, and full data transparency, among others). Management decisions based on sound scientific reasoning are needed to address the legitimate concerns surrounding dFAD use and ensure the sustainability of both pelagic and coastal ecosystems and tropical tuna PS fisheries. [ABSTRACT FROM AUTHOR]

Mapping and predicting the potential risk of fishing activities to large marine protected areas (MPAs), where management capacity is low but fish biomass may be globally important, is vital to prioritizing enforcement and maximizing conservation benefits. Drifting fish aggregating devices (dFADs) are a highly effective fishing method employed in purse seine fisheries that attract and accumulate biomass fish, making fish easier to catch. However, dFADs are associated with several negative impacts, including high bycatch rates and lost or abandoned dFADs becoming beached on sensitive coastal areas (e.g., coral reefs). Using Lagrangian particle modeling, we determined the potential transit of dFADs in a large MPA around the Chagos Archipelago in the central Indian Ocean. We then quantified the risk of dFADs beaching on the archipelago's reefs and atolls and determined the potential for dFADs to pass through the MPA, accumulate biomass while within, and export it into areas where it can be legally fished (i.e., transit). Over one‐third (37.51%) of dFADs posed a risk of either beaching or transiting the MPA for >14 days, 17.70% posed a risk of beaching or transiting the MPA for >30 days, and 13.11% posed a risk of beaching or transiting the MPA for >40 days. Modeled dFADs deployed on the east and west of the perimeter were more likely to beach and have long transiting times (i.e., posed the highest risk). The Great Chagos Bank, the largest atoll in the archipelago, was the most likely site to be affected by dFADs beaching. Overall, understanding the interactions between static MPAs and drifting fishing gears is vital to developing suitable management plans to support enforcement of MPA boundaries and the functioning and sustainability of their associated biomass. Article impact statement: Left unchecked, drifting fish aggregation devices could reduce the efficacy of static marine protected areas. [ABSTRACT FROM AUTHOR]

Recently, several large marine protected areas (MPAs) have been established globally, and it is hoped that they will aid the recovery of populations of highly mobile, large pelagic species. Understanding the distribution of these species within MPAs is key to delivering effective management, but monitoring can be challenging over such vast areas of open ocean.Historical fisheries data, collected prior to MPA establishment, can provide an insight into the past distributions of target species. We investigated the spatial and temporal distribution of yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) tuna catch using logbook data from the purse seine fishery in the British Indian Ocean Territory from 1996 to 2010, before it was established as an MPA in April 2010.Generalized additive models were used to predict tuna presence and relative abundance from fishing records in relation to temporal and environmental variables. Significant variables included sea salinity, temperature, and water velocity.Predictions from the models identified a distinct hotspot for large yellowfin tuna within the MPA, and areas of high predicted relative abundance of skipjack tuna. We recommend that these areas are used as focal points from which populations can be monitored and investigations into tuna residency time can occur, so that the effectiveness of the MPA in conserving highly mobile pelagic fish can be determined. [ABSTRACT FROM AUTHOR]

Abstract Fish aggregating devices (FADs) have over recent decades, become an integral tool in commercial tuna fisheries due to their increased efficiency over free school catches. Technological development has further aided in their increased usage and reliance by many fleets. The negative consequences of FADs include higher rates of non-target species such as juvenile bigeye and yellowfin tunas. Management of this negative consequence has to date been undertaken by spatial and/or temporal closures to fishing. These closures can result in an economic burden to fishermen via reduced catch rates, coastal states trying to sell access rights to fishing grounds at the same rate with no closure in place, and canneries through variability in supply and subsequent volatility in market prices. This paper examines the economic benefits of replacing closures with FAD set limits which place a hard limit on the total number of FAD sets that can be made in any given period. The analysis indicates that economic gains can be achieved at all levels of the supply chain from the fishing vessel through to the consumer. Highlights • FAD closures cause an economic burden on all parts of the supply chain. • FAD set limits can achieve the same environmental outcome. • FAD set limits can reduce the economic burden across the supply chain. [ABSTRACT FROM AUTHOR]

This research focuses on the description of the spatial and temporal distributions of mobulid ray species (Mobula birostris, Mobula mobular, Mobula thurstoni, Mobula tarapacana and Mobula munkiana) using data from the observer program (1993-2014) of the Inter-American Tropical Tuna Commission (IATTC). The tuna purse seine operations in the region extend from 70 to 150°W to 20°S-30°N. Significant differences on the captures per sets between fishing modes and species were found. Results showed that the most common species taken are M. thurstoni, M. mobular and M. birostris in School sets (sets on unassociated tuna schools). The temporal distributions showed high variability of the catches by species and years. The spatial distribution showed several areas of importance depending of the type of fishing, such as the coast of Peru, Galagapos or the Costa Rica Dome, and possible relationships with some oceanographic processes of the eastern Pacific Ocean (i.e. coastal and seasonal upwelling systems). The frequency of the captures per set showed that, although the greatest numbers caught in a set were very low (around 53.7% of sets with one capture), in some areas and periods there were captures of aggregates of hundreds of individuals of some of these species, such as Galapagos Islands during December, Costa Rica Dome during August, or Baja California during June. These events are of biological interest, and may offer good opportunities for conservation. This project has been developed with the aim of identifying the most important areas for these bycatch species and thus, improving the knowledge on them to reduce their mortality. [ABSTRACT FROM AUTHOR]

Concerns about the ecological impact of recent increases in the use of drifting fish-aggregating devices (FADs) have led to implementation of FAD limits worldwide in purse-seine fisheries targeting tropical tunas. However, quantitative analyses supporting such management measures are needed. Analyses of observer data for purse-seine vessels operating in the eastern Pacific Ocean (EPO) during 2012–2015 were conducted. FAD fishing strategies identified in this analysis were found to vary with distance to the coast. Vessels that operated furthest offshore made a large number of FAD deployments and fished primarily on FADs they deployed themselves. Vessels that operated closest to the coast made the fewest FAD deployments and fished about equally on FADs they deployed themselves and on FADs deployed by other vessels. Independent of the FAD fishing strategy, the estimated relationship between deployments and sets was increasing but nonlinear, with a reduced rate of return beyond about 200 deployments. An analysis of the relationship between deployments and standardized catch per successful set, however, provided some support for the hypothesis that more deployments may allow vessels to optimize fishing efficiency. These results highlight the complexity of EPO FAD fishing strategies and have management implications for limits on FAD usage globally. [ABSTRACT FROM AUTHOR]

Monitoring and managing fisheries bycatch is increasingly recognized as a critical component of robust fisheries management frameworks. This review, addressing this subject, begins by defining bycatch and analyzing the reasons it happens, from accidental to intentional discarding. It identifies the most common species composing bycatch of the main tuna fisheries using purse seine and longline gear. Considerations of options available to estimate bycatch, their potential biases and uncertainties, and ways to address these issues are discussed. The formulas used to estimate bycatch also point to the options to reduce them, lowering bycatch per unit of effort or lowering effort itself. It shows that a mean can be reduced by reducing all its component figures, or by eliminating the high values at the extreme of the distribution (i.e., where a small proportion of events causes a large proportion of the problem), a common issue in bycatch. A generic strategy is described that can be applied to all gears and fisheries, and it is then described for the fisheries of interest, showing examples of its application. These cover many mitigation actions based on gear and operational changes. Management options aiming at reducing bycatch are also mentioned. A detailed description of the ways the strategy has been implemented for purse seiners and longliners is provided. Finally, market strategies, education and awareness of stakeholders, mainly fishers, and some potential future developments are briefly described. [ABSTRACT FROM AUTHOR]

Understanding the relationship between environmental variables and pelagic species concentrations and dynamics is helpful to improve fishery management, especially in a changing environment. Drifting fish aggregating device (DFAD)-associated tuna and non-tuna biomass data from the fishers’ echo-sounder buoys operating in the Atlantic Ocean have been modelled as functions of oceanographic (Sea Surface Temperature, Chlorophyll-a, Salinity, Sea Level Anomaly, Thermocline depth and gradient, Geostrophic current, Total Current, Depth) and DFAD variables (DFAD speed, bearing and soak time) using Generalized Additive Mixed Models (GAMMs). Biological interaction (presence of non-tuna species at DFADs) was also included in the tuna model, and found to be significant at this time scale. All variables were included in the analyses but only some of them were highly significant, and variable significance differed among fish groups. In general, most of the fish biomass distribution was explained by the ocean productivity and DFAD-variables. Indeed, this study revealed different environmental preferences for tunas and non-tuna species and suggested the existence of active habitat selection. This improved assessment of environmental and DFAD effects on tuna and non-tuna catchability in the purse seine tuna fishery will contribute to transfer of better scientific advice to regional tuna commissions for the management and conservation of exploited resources. [ABSTRACT FROM AUTHOR]

Catch and fishing effort time series are used by managers to safeguard the availability of resources in the future. Fisheries organizations estimate the status of a stock and the levels for sustainable harvest. Based on these indicators, regulations are developed to guarantee the availability of food and sustain economic growth. For example, tuna stocks are important not only in terms of nutrition, but also for the welfare, culture, revenue, and employment of the countries that rely upon them. However, fisheries time-series are the result of many natural and non-natural factors and are usually difficult to predict. Here, we propose a method to aggregate fisheries time series in space and time, to detect hidden periodicities, to predict the time series in the future and to identify the most stressed locations in the fishing area. We apply our method to tuna fisheries data in the Indian Ocean and compare it with respect to other methods. We demonstrate that the method is able to highlight periodic patterns in this high fishing activity area and to forecast the fisheries time series in the future. We use a research e- Infrastructure to comply with modern approaches supporting reproducibility, repeatability, and results sharing. [ABSTRACT FROM AUTHOR]

The certification by the Marine Stewardship Council of the unassociated-sets purse seine fishery of the Parties to the Nauru Agreement (PNA) has the potential to improve stocks of the fishery's main three tuna species, as well as to allow the PNA to extract more resource rents from the fishery. In this paper we analyze the economic and biological effects of this certification with a tractable bioeconomic model. We find that under plausible assumptions certification of tuna from the PNA unassociated-sets purse seine fishery can enhance stock size of skipjack tuna and bigeye tuna, but is likely to reduce stocks of yellowfin tuna due to the unassociated-sets fishery's high catch rate for this stock. The PNA's access fee declines in most scenarios considered. [ABSTRACT FROM AUTHOR]

Drifting Fish Aggregating Devices (dFADs) are currently made with synthetic and non-biodegradable materials contributing to the increase of marine litter and other potential ecosystem impacts. Tuna RFMOs have promoted the research and progressive replacement of existing FADs by non-entangling biodegradable FADs (bioFADs). Here, we present the results of the first large-scale biodegradable FAD project in the Indian Ocean to develop and implement the use of non-entangling biodegradable dFADs. The bioFAD tested were fully non-entangling without netting minimizing completely the risk of entanglement. Tested bioFADs significantly contribute to the reduction of the synthetic plastic-based materials, increase the use of biodegradable materials and reduce the total material weight used in FADs, reducing their overall ecosystem impacts. The results of testing 771 bioFADs in real fishing conditions, showed that the fishing performance regarding presence/absence of tuna around dFADs, first day of tuna detection, proportion of FADs occupied by tuna, biomass aggregation underneath the FADs and catch per set between bioFADs and conventional dFADs were similar. This provides support for the efficacy of bioFADs regardless of the degradation experienced by the biodegradable materials tested. Although some bioFADs lasted up to one year, the degradation of the biodegradable material was important and some bioFADs lost their original structure after the study period, suggesting the need to find alternative designs for bioFADs that will suffer less structural stress than those bioFADs made of biodegradable material but with conventional design. The lessons learnt in this large-scale trial will contribute to refining the future designs of biodegradable FADs. • First large-scale biodegradable FAD project for tropical tuna fisheries in the Indian Ocean. • Tested biodegradable FADs were fully non-entangling dFADs without netting, which minimized completely the risk of entanglement. • Tested biodegradable FADs significantly contribute to the reduction of synthetic plastic-based materials. • Tested biodegradable FADs increase the use of biodegradable materials. • Tested biodegradable FADs reduce the total material weight used, reducing the overall ecosystem effects of FADs. [ABSTRACT FROM AUTHOR]

Abstract: Several tuna regional fisheries management organizations (t-RFMOs) have adopted retention requirements for skipjack, bigeye and yellowfin tunas caught by purse seine vessels to reduce discards, create disincentives to catch small fish, and incentivize the development and adoption of more selective technologies. Although retention policies in the t-RFMOs have been limited to target tunas in purse seine fisheries, some have advocated for an expansion of those policies, and t-RFMOs could consider expanding retention policies to a greater number of species and/or to other gear types. This paper discusses the benefits and costs of broader retention policies for purse seine and longline tuna fisheries in the western and central Pacific Ocean (WCPO). Using bycatch data from observers and logbooks from the U.S. purse seine and longline fleets operating in the WCPO, this paper documents the types and magnitude of fish discarded. For the purse seine fishery, this information was used to estimate direct impacts of having to off-load at the initial point of landing in key Pacific Island ports. For the longline fishery, estimates of direct impacts were limited to Honolulu and Pago Pago, American Samoa, the two primary ports where U.S. catch is landed. Expanding retention policies beyond the target tunas and to other gear types would further reduce discarding and possibly provide stronger incentives to develop and use more selective techniques. Beyond impacts to the ecosystem and fisher behavior, adopting broader retention policies may have other implications, and this paper explores those implications on vessels, processors, and communities. In general, as is the case with most direct interventions on fishing operations, there will be both benefits and costs, and the magnitude of those impacts will depend on the scope and extent of any expanded retention policy. [Copyright &y& Elsevier]

The use of fish aggregating devices ( FADs) by purse seine fisheries has come under increasing criticism for its potential deleterious impacts on tuna stocks, for high levels of by-catch and threats to the biodiversity of tropical pelagic ecosystems. Here, we review the current state of scientific knowledge of this fishing technique and current management strategies. Our intent is to encourage objective discussion of the topic and highlight areas worthy of future research. We show that catching juvenile tuna around FADs does not necessarily result in overfishing of stocks, although more selective fishing techniques would likely help obtain higher yield. Levels of non-tuna by-catch are comparable to or less than in other commercial tuna fisheries and are primarily comprised of species that are not considered threatened. Accordingly, to minimize impacts on ecosystem balance, there is merit in considering that all species captured in purse seine fisheries (excluding vulnerable species such as turtles and sharks) should be retained, but the consequences of such a measure should be carefully examined before implementation. The take of vulnerable species could be further reduced by introduction of additional mitigation measures, but their potential benefits would be limited without parallel efforts with other gears. Finally, there is no unequivocal empirical evidence that FADs represent an 'ecological trap' that inherently disrupts tuna biology although further research should focus on this issue. We encourage RFMOs to expand and improve their FAD management plans. Under appropriate management regimes, FAD fishing could be an ecologically and economically sensible fishing method. [ABSTRACT FROM AUTHOR]

Abstract: Tuna purse seining in the Pacific Islands region is the world’s largest tuna fishery. Currently some organizations are publicising the desirability of replacing at least some of the purse seining with pole-and-line fishing—a technique which requires significant quantities of live baitfish. This research was undertaken to determine the quantity of baitfish required to replace purse seining. It is estimated that to catch a million tonnes of tuna annually in the Pacific Islands region (i.e. replace the purse seine fishery) would require about 31,250t of baitfish per year. Historical catches of baitfish suggest that catches this large may not be possible. There is also some question of the practicality and desirability of a substantial increase in baitfish harvesting in the region. [ABSTRACT FROM AUTHOR]