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Purpose: The Comorian fisheries land around 20 000 t fish annually, for the domestic market. The fleet is divided into a handful of segments, all of them artisanal in nature and practices, using a variety of gear and fishing strategies. Some fishers use fish aggregating devices installed in the territorial waters. This study aims at understanding the comparative environmental impacts of the Comorian fisheries segments, as well as the efficiency of fisheries operations as compared with similar fisheries and alternative sources of animal proteins for the domestic population. Material and methods: This study applied life cycle assessment to estimate, comparatively, the environmental impacts of the different types of fishing unit, segregated by island, boat size and gear, as well as against alternative sources of protein for the Comorian population and neighbouring artisanal fisheries. Results and discussion: Comorian fisheries, whose landings are dominated by tunas, seem less efficient than other regional small-scale fisheries and feature higher environmental impacts than alternative animal protein sources available in the country. The widely adopted practice of trolling, highly energy intensive, dominates Comorian fisheries. Passive gear-based fishing strategies also feature higher than expected energy-related impacts. The environmental benefits of using fish aggregating devices are not clear. The impacts on biodiversity are a cause for concern, especially in the reef areas off Mohéli. Conclusions: Given the cost of public investment on FADs, the fragility of the devices (a FAD can be lost or become ineffective fairly quickly if it is not maintained), and the supposedly significant impact of the FAD network on domestic tuna fishing yields, data on FADs is essential for decision-makers. Other elements for fisheries decision-makers, which are currently lacking, include the monitoring of octopus and reef fish stocks, the effect of co-management agreements on stocks and ecosystems, and a sustainable data collection strategy. The latter would be helpful to better understand the relative importance of fishing strategies, particularly FADs, in relation to fuel intensity. Improving the Comorian fishery's efficiency would be a key driver to improve its sustainability. [ABSTRACT FROM AUTHOR]

Tropical tuna fisheries support some of the largest artisanal and industrial fisheries worldwide. Approximately 37% of the tropical tuna catch by industrial purse seiners is obtained from tuna associated with drifting fish aggregating devices (DFADs), where three tuna species coexist: skipjack (Katsuwonus pelamis) , bigeye (Thunnus obesus), and yellowfin tuna (Thunnus albacares) , with stocks subject to different health status. Purse seine fishers heavily rely on acoustic technology to detect and assess the quantity of tuna at DFADs. Yet, accurately distinguishing between species using solely acoustic methods is limited by insufficient knowledge about each species' acoustic response across frequencies. This study was carried out on six swimbladdered individuals belonging to two sets with mean lengths of 51.9 ± 9.5 and 52.9 ± 2 cm. It focuses on the frequency response obtained from ex situ measurements of yellowfin tuna recorded at 38, 70, 120, and 200 kHz, which revealed a flat response across frequencies, with b20 values of −72.4 ± 9, −73.2 ± 8, -72.3 ± 8, and −72.3 ± 9 dB, respectively. These results, contrast with previous findings on bigeye and skipjack, demonstrating the discrimination potential of acoustics in these three species. To harness this potential, a discrimination algorithm was developed. [ABSTRACT FROM AUTHOR]

Purse‐seine fishers using drifting fish aggregating devices (dFADs), mainly built with bamboo, plastic buoys, and plastic netting, to aggregate and catch tropical tuna, deploy 46,000–65,000 dFADs per year in the Pacific Ocean. Some of the major concerns associated with this widespread fishing device are potential entanglement of sea turtles and other marine fauna in dFAD netting; marine debris and pollution; and potential ecological damage via stranding on coral reefs, beaches, and other essential habitats for marine fauna. To assess and quantify the potential connectivity (number of dFADs deployed in an area and arriving in another area) between dFAD deployment areas and important oceanic or coastal habitat of critically endangered leatherback (Dermochelys coriacea) and hawksbill (Eretmochelys imbricata) sea turtles in the Pacific Ocean, we conducted passive‐drift Lagrangian experiments with simulated dFAD drift profiles and compared them with known important sea turtle areas. Up to 60% of dFADs from equatorial areas were arriving in essential sea turtle habitats. Connectivity was less when only areas where dFADs are currently deployed were used. Our simulations identified potential regions of dFAD interactions with migration and feeding habitats of the east Pacific leatherback turtle in the tropical southeastern Pacific Ocean; coastal habitats of leatherback and hawksbill in the western Pacific (e.g., archipelagic zones of Indonesia, Papua New Guinea, and Solomon Islands); and foraging habitat of leatherback in a large equatorial area south of Hawaii. Additional research is needed to estimate entanglements of sea turtles with dFADs at sea and to quantify the likely changes in connectivity and distribution of dFADs under new management measures, such as use of alternative nonentangling dFAD designs that biodegrade, or changes in deployment strategies, such as shifting locations. [ABSTRACT FROM AUTHOR]

Catch per unit of fishing effort (CPUE) is often used as an indicator of tuna abundance, where it is assumed that the two are proportional to each other. Tuna catch is therefore typically simplified in tuna population dynamics models and depends linearly on their abundance. In this paper, we use an individual-based model of tuna and their interactions with drifting Fish Aggregating Devices (dFADs) to identify which behavioural, ocean flow, and fishing strategy scenarios lead to an emergent, non-linear dependency between catch, and both tuna and dFAD density at the ∼1○ grid scale. We apply a series of catch response equations to evaluate their ability to model associated catch rate, using tuna and dFAD density as terms. Our results indicate that, regardless of ocean flow, behavioural, or fisher strategy scenario, simulated catch is best modelled with a non-linear dependence on both tuna and dFAD abundance. We discuss how estimators of CPUE at the population scale are potentially biased when assuming a linear catch response. [ABSTRACT FROM AUTHOR]

We investigated the associative behavior of skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares), and bigeye (T. obsesus) tuna within multi‐species aggregations associated with drifting fish aggregating devices (dFADs) in two different regions of the western Indian Ocean: the Mozambique Channel and the Seychelles, using acoustic telemetry. We documented the residence and absence times of tunas at two temporal scales (coarse and fine scale) and made comparisons between regions. A total of 56 tunas were tagged and released at 7 different dFADs (4 in the Mozambique Channel and 3 in the Seychelles) during four research cruises. We recorded the first observations of skipjack tuna making excursions of more than 24 hours away from dFADs before returning and confirmed findings of other studies showing that yellowfin tuna can make long excursions (4.07 days) before returning to their home dFADs. Combining both studied regions, average residence times were 7.59 days (min 0.03; max 16.49), 6.64 days (min 0.01; max 26.72), and 4.58 days (min 0.09; max 18.33) for bigeye, yellowfin, and skipjack tuna, respectively. Exponential models best fitted the residence times for all three tuna species, indicating time‐independent probabilities of departure from dFADs. For yellowfin tuna, at a coarse temporal scale, no regional differences were observed in the residence times. However, at a fine temporal scale, regional differences were apparent in both residence and absence times. This study provides new information on the associative behavior of tunas at dFADs in the Indian Ocean which is key to improving the science‐based management of dFADs. [ABSTRACT FROM AUTHOR]

Juvenile silky sharks (Carcharhinus falciformis) regularly associate with floating objects yet the reasons driving this behaviour remain uncertain. Understanding the proportion of time that silky sharks spend associated with floating objects is essential for assessing the impacts of the extensive use of fish aggregating devices (FADs) in the tropical tuna purse‐seine fisheries, including increased probability of incidental capture and the potential of an ecological trap.Previous studies provided insight into the amount of time that silky sharks spent at an individual FAD but were unable to assess neither the time spent between two associations nor the proportion of time spent associated/unassociated.The percentage of time that juvenile silky sharks spend unassociated with floating objects was estimated through the analysis of horizontal movements of 26 silky sharks monitored with pop‐up archival tags. Under the assumption that a high association rate with drifting FADs would align the trajectories of tracked sharks with ocean surface currents, a novel methodology is proposed, based on the comparison of shark trajectories with simulated trajectories of passively drifting particles derived using a Lagrangian model.Results revealed that silky shark trajectories were divergent from surface currents, and thus unassociated with FADs, for at least 30% of their time. The potential of the methodology and the results are discussed in the context of increasing FAD densities in the Indian Ocean. [ABSTRACT FROM AUTHOR]

Man-made floating objects in the surface of tropical oceans, also called drifting fish aggregating devices (DFADs), attract tens of marine species, including tunas and non-tuna species. In the Indian Ocean, around 80% of the sets currently made by the EU purse-seine fleet are on DFADs. Due to the importance and value of this fishery, understanding the habitat characteristics and dynamics of pelagic species aggregated under DFADs is key to improve fishery management and fishing practices. This study implements Bayesian hierarchical spatial models to investigate tuna and non-tuna species seasonal distribution based on fisheries-independent data derived from fishers’ echo-sounder buoys, environmental information (Sea Surface Temperature, Chlorophyll, Salinity, Eddie Kinetic Energy, Oxygen concentration, Sea Surface Height, Velocity and Heading) and DFAD variables (DFAD identification, days at sea). Results highlighted group-specific spatial distributions and habitat preferences, finding higher probability of tuna presence in warmer waters, with higher sea surface height and low eddy kinetic energy values. In contrast, highest probabilities of non-tuna species were found in colder and productive waters. Days at sea were relevant for both groups, with higher probabilities at objects with higher soak time. Our results also showed species-specific temporal distributions, suggesting that both tuna and non-tuna species may have different habitat preferences depending on the monsoon period. The new findings provided by this study will contribute to the understanding of the ecology and behavior of target and non-target species and their sustainable management.

A key challenge in small-scale fisheries that use moored fish aggregating devices (mFADs) is the ability to accurately quantify multi-sector fishing activity through fishery-independent methods. Here, we present a novel fishery-independent assessment of multi-sector fishing activity associated with a newly developed open access mFAD programme off San Juan, Puerto Rico. We identified three fishing sectors (recreational, charter and commercial) and 158 individual fishing vessels that routinely operated in the vicinity of the mFADs. The results indicate that daytime fishing activity varied by time of day, day of week, location and sector. During fishing tournaments, the data revealed that fishing activity increased threefold; across monitoring periods, for-hire charter vessels were the most consistent day-to-day user segment, and recreational activity peaked on weekends. Our study represents a new technique for rapidly identifying and detecting multi-sector fishing activity near mFADs and highlights the potential to gather comparable data wherever mFADs are deployed. The results are used to discuss how this technique can be used to assess the performance of mFADs to identify sector overlap and guide management in determining deployment patterns and facilitate the design of cost-effective surveys to estimate mFAD vessel activity, and potentially catch, of mFAD-associated species.

Abstract Importance of participatory approaches in the management of small-scale fisheries is being increasingly highlighted today throughout the world. Brush park fishery in Negombo estuary, Sri Lanka is a small-scale fishery where traditional ecological knowledge (TEK) accumulated over generations is utilized to optimize the harvests. In the present study, the institutional robustness of the community-based management system of this fishery, which is based on TEK was assessed using Ostrom's modified design principles. Results showed that the degree of community-based management is not effective in successful management of this fishery due to common pool nature. Nevertheless, there is potential for integrating some institutional design principles through intervention of centralized management authorities. As such, co-management regimes that empower local communities are needed for the sustainability this fishery. Highlights • Fishers use traditional ecological knowledge for resource management. • Brush park fishers in a Sri Lankan estuary possess a legacy of traditional knowledge. • Management mechanisms were assessed for compliance with Ostrom's design principles. • Community-based management is not sufficient to govern common pool resources. • Co-management regimes are needed to ensure sustainability of brush park fishery in the Negombo estuary, Sri Lanka. [ABSTRACT FROM AUTHOR]

Knowledge of aquaculture–environment interactions is essential for the development of a sustainable aquaculture industry and efficient marine spatial planning. The effects of fish and shellfish farming on sessile wild populations, particularly infauna, have been studied intensively. Mobile fauna, including crustaceans, fish, birds and marine mammals, also interact with aquaculture operations, but the interactions are more complex and these animals may be attracted to (attraction) or show an aversion to (repulsion) farm operations with various degrees of effects. This review outlines the main mechanisms and effects of attraction and repulsion of wild animals to/from marine finfish cage and bivalve aquaculture, with a focus on effects on fisheries‐related species. Effects considered in this review include those related to the provision of physical structure (farm infrastructure acting as fish aggregating devices (FADs) or artificial reefs (ARs), the provision of food (e.g. farmed animals, waste feed and faeces, fouling organisms associated with farm structures) and some farm activities (e.g. boating, cleaning). The reviews show that the distribution of mobile organisms associated with farming structures varies over various spatial (vertical and horizontal) and temporal scales (season, feeding time, day/night period). Attraction/repulsion mechanisms have a variety of direct and indirect effects on wild organisms at the level of individuals and populations and may have implication for the management of fisheries species and the ecosystem in the context of marine spatial planning. This review revealed considerable uncertainties regarding the long‐term and ecosystem‐wide consequences of these interactions. The use of modelling may help better understand consequences, but long‐term studies are necessary to better elucidate effects. [ABSTRACT FROM AUTHOR]

Abstract The multiple Traveling Salesman Problem (mTSP) is a widespread phenomenon in real-life scenarios, and in fact it has been addressed from multiple perspectives in recent decades. However, mTSP in dynamic circumstances entails a greater complexity that recent approaches are still trying to grasp. Beyond time windows, capacity and other parameters that characterize the dynamics of each scenario, moving targets is one of the underdeveloped issues in the field of mTSP. The approach of this paper harnesses a simple prediction method to prove that integrating forecasting within a metaheuristic evolutionary-based method, such as genetic algorithms, can yield better results in a dynamic scenario than their simple non-predictive version. Real data is used from the retrieval of Fish Aggregating Devices (FADs) by tuna vessels in the Indian Ocean. Based on historical data registered by the GPS system of the buoys attached to the devices, their trajectory is firstly forecast to feed subsequently the functioning of a genetic algorithm that searches for the optimal route of tuna vessels in terms of total distance traveled. Thus, although valid for static cases and for the Vehicle Routing Problem (VRP), the main contribution of this method over existing literature lies in its application as a global search method to solve the multiple TSP with moving targets in many dynamic real-life optimization problems. [ABSTRACT FROM AUTHOR]

Fish aggregating devices (FADs) have been widely used by commercial fisheries to increase the catchability of pelagic stocks in the open sea. FADs have the potential to enhance nearshore small-scale fisheries where stocks are often overfished. This study examined changes in catch composition, abundance, catch and effort, and aspects of diversity in Kenya's nearshore coastal fisheries after deployment of anchored fish aggregating devices (AFADs). The study combined both fishery independent and dependent methods in assessing changes in fish assemblages post-deployment. Results showed orders of magnitude increase in length, weight, commercial value, and catch per unit effort (CPUE) of landed catch after deployment of FADs suggesting that FADs had a positive effect on the local fishery. Species richness at FAD sites increased post-deployment (n = 281) compared to pre-deployment values (n = 223). Simultaneous use of several complementary structural indices may be required in order to accurately describe and monitor fish assemblages around the FADs. The findings suggest that AFADs are capable of creating both short and long-term impacts on livelihoods, with the potential to deflect pressure on the overfished nearshore fish stocks. However, more research will be needed on redistribution of fish around FADs, design and placement configuration, and site selection amongst others. [ABSTRACT FROM AUTHOR]

The conservation benefits of the Galapagos Marine Reserve (GMR), created in March 1998, have been consistently proved for endemic species and populations with limited movements. Yet, to date, no study has explored its effects on highly-migratory pelagic species, such as tuna. To this end, the impact of the GMR on the behavior and productivity of tuna fisheries in this region is analyzed. After considering other potential factors, which occurred approximately over the same period (i.e. increase of fleet size, changes in fishing technology, and climatic events, among others), it was found that the creation of the GMR increased fishing productivity in both the Galapagos Exclusive Economic Zone (EEZ) surrounding the GMR, as well as inside the marine reserve. However, the effect was heterogenous among tuna species – the GMR had a positive impact on the fishing productivity of yellowfin tuna (YFT) and skipjack tuna (SKJ) fisheries, but did not have any significant effect on that of bigeye tuna (BET). Then, it is proposed that the GMR effect might be dissipated by the overuse of Fish Aggregating Devices (FADs), especially in the case of BET. [ABSTRACT FROM AUTHOR]

The structure, materials and designs of drifting Fish Aggregating Devices (dFADs) have generally remained rudimentary and relatively unchanged since they first came into use in the 1980 s. However, more recently, dFADs have been increasing in dimensions and the prevailing use of plastic components. Abandoned, lost or discarded dFADs can therefore contribute to the global marine litter problem. Transitioning to biodegradable and non-toxic materials that have a faster rate of decomposition, and are free of toxins and heavy metals, relative to synthetic materials, has been prescribed as an important part of the solution to reducing marine pollution from industrial tuna fisheries that rely on dFADs. This review of the current state of dFADs considers aspects related to the use of biodegradable materials in their construction, including; regulations related to dFAD materials, trials of biodegradable designs and materials and future alternatives. During the last decade, regulatory measures at tuna Regional Fishery Management Organizations (tRFMOs) have gradually moved towards the clear recommendation to use biodegradable materials in dFAD construction together with other measures limiting the number of active dFADs and the use of netting materials. However, to provide operational guidance, more clarity is needed, starting with a standardised definition of biodegradable dFADs among tRFMOs. Research involving dFAD natural and synthetic materials is required, along with improved data collection for monitoring the transition of dFAD materials against specified standards for biodegradable dFADs. In addition, alternative and complementary actions need to be explored to contribute to minimising adverse effects of dFADs on the environment. Acknowledging the current difficulties for the implementation of fully biodegradable dFADs in tuna fisheries, a stepwise process towards the implementation of commercially viable biodegradable dFADs should be considered. [ABSTRACT FROM AUTHOR]

The Fishing Industry in the Philippines plays an important role in the food and employment need of Filipino fishers. By using anchored Fish Aggregating Devices (FADs or payao), the Philippine tuna fisheries was transformed into a million-dollar industry. Minimal studies on exploitation rates and fish behavior around anchored FADs hampered further understanding of this fishery practice. Studies on fish behavior using Local Ecological Knowledge (LEK) are good complement where data is limited. A study using semi-structured interview (n = 46) and three focus group discussions (n = 39 participants) to record fishers' knowledge and observations on the behavior of different fish species around anchored FADs was conducted. This particularly focused on attraction, retention, and departure behavior of fishes in identified FAD sites. Based on the fishers' knowledge, tuna schools are attracted to anchored FADs at 10 km distance. In anchored FADs, tuna form schools segregated by species and size. There was no relationship between the attraction distance and the reported school size and the various waiting times for fish to aggregate below the FADs. There was no variation between the species present at day or night time although fishers have reported a distinction of species found near the surface (0–10 m) and those found at other depths (11–20 m). Juvenile yellowfin tuna (Thunnus albacares), skipjack (Katsuwonus pelamis), and frigate and bullet tunas (Auxis spp.) are found to stay at 25–50 m from the FAD at a depth of >20 m. Adult oceanic tunas reside in deeper waters (75 m). The fish visual census produced similar results with the semi-structured interviews and FGDs but did not observe oceanic tunas at depths of 15–20 m in the anchored FADs examined.

Decline in tuna fish stocks due to weak enforcement of regulations on fishing effort poses a challenge to the sustainability of tuna fishery. Intervention programs to address this problem require an understanding of the operational behaviour of the fishers and how various socioeconomic factors may impact fishers’ decisions to continue or discontinue their fishing efforts. A semi-structured interview questionnaire was developed to find whether fishers are willing to keep, change their fishing strategies or exit the fishery if their regular catch will decline by half. Boat captains, assistant boat captains and crew from General Santos City, Lupon, Mati City and Governor Generoso in the Philippines (n=293) were purposively selected for interviews. Results show that fishers from General Santos City with ancillary industries and Lupon with fewer economic development are more willing to adapt or change their fishing strategies. The catch value or price was found to have a strong influence on the likelihood that anchored FAD tuna fishers will adapt or change their fishing strategy when their catches decline. Fishers whose catch fetched a price of PhP 151.00 (US$ 3.48) and above Php 200 (US$ 4.61) have 80% probability to change their fishing strategy. The proportion of catch sold also had a high influence on the decisions to adapt in the fishery with fishers selling 36% and 73% of their catches have 100% and 70% probability to adapt. The results suggest a reluctance to exit the fisheries even when tuna fishing is no longer economically viable, fishers opt to adapt. [ABSTRACT FROM AUTHOR]

Drifting Fish Aggregating Devices (dFAD) are widely used in purse seine tuna fisheries globally. DFADs are often lost or abandoned by the fishing industry which can lead to marine pollution, entanglement of sensitive species and habitat damage. They are considered as a high-risk lost or abandoned fishing gear due to their common construction with long-lasting synthetic materials, including netting. This study used data collected by fishery observers to investigate materials and designs used in dFAD construction over the last 10 years in the Western and Central Pacific Ocean (WCPO). Results indicated that apart from bamboo, which is commonly used in dFAD rafts with other synthetic materials for buoyancy, very few natural materials are used. The depth of dFAD appendages varied, with a median of 50 m. Most dFADs used netting of various mesh sizes in some aspect of their construction. There is limited information to assess the uptake of lower entanglement risk dFAD designs. Transition towards more environmentally friendly dFAD designs is being promoted by management measures imposed by the Western and Central Pacific Fisheries Commission that include banning of netting by 2024 and encouraging the use of natural materials. Scientific trials are underway to support industry adoption of biodegradable dFAD materials. This paper provides important baseline data to detect and monitor future changes in dFAD construction and materials in response to management measures, and also highlights limitations to data collected by observers that will need to be improved to better monitor these changes. • DFADs in the Western and Central Pacific Ocean (WCPO) are currently constructed from predominately synthetic materials. • Netting remains a dominant material used in dFADs in the WCPO, including the use of larger mesh sizes. • Observer data was valuable to quantify trends in DFAD materials, but reporting of materials/designs pre-deployment is needed. • Transition to non-entangling/biodegradable dFAD designs in the WCPO is just beginning. • This paper provides a baseline to detect and monitor future changes in dFAD construction in the WCPO. [ABSTRACT FROM AUTHOR]

The fisheries sectors in Vanuatu and Timor-Leste are important sources of food and income. Similar to other developing countries and those in the Pacific, they are vulnerable to the impacts of climate change more so because of their geographic location, socioeconomic conditions and political instability. Nonetheless, there are approaches to alleviate the damaging effects of climate change in the region's fisheries sector. Using economic modeling, this paper estimates the economic costs of potential climate change adaptation strategies for the fisheries sector in Vanuatu and Timor-Leste through assessment of alternative future scenarios. Strategies include aquaculture development, natural resource management through establishment and/or expansion of marine protected areas, and deployment of low-cost inshore fish aggregating devices. Modeling results demonstrate that the above innovations will enable the two countries to significantly improve coastal and freshwater fish production in the medium-term (2035) and long-term (2050). Fish consumption is projected to grow due to population and income improvements; yet considerable increases in production will augment demand. Furthermore, national-level gains are projected from these adaptation strategies through fish exports. Improved production under climate change will require significant investments from the national governments of Vanuatu and Timor-Leste and/or private sectors. [ABSTRACT FROM AUTHOR]

Capture fisheries and aquaculture sectors have played major roles in the national economy and food security of Fiji. But climate change may place substantial stress on these sectors within this archipelago. This paper assesses the potential economic impact of two important climate change adaptation strategies in Fiji, natural resource management (NRM) and aquaculture, using a market fish supply–demand model. The model undertakes a comparative analysis of alternative fisheries development scenarios for 2035 and 2050, while taking account of the impact of climate change on the fisheries sector. The modeling and scenario analyses show that promoting aquaculture can help raise aggregate fish production, consumption, and trade. However, the required increases in aquaculture could be massive. While aquaculture development alone is unlikely to meet the growing excess demand for fish in Fiji, it will be an important component in adapting to the negative effects of climate change on capture fisheries. Various NRM strategies, such as marine protected areas (MPAs) and locally managed marine areas (LMMAs), are projected to have positive impacts in Fiji, expanding the stock and catch of fish. But current efforts on various NRM strategies are too small to have any meaningful impact to reverse the declining trends of coastal fisheries catch. Efforts would need to be greatly scaled-up to achieve significant production gains. [ABSTRACT FROM AUTHOR]

The use of fish aggregating devices (FADs) has intensified markedly throughout the world’s tropical and sub-tropical oceans since early 1990s. While information on large-scale industrial FADs focusing on capturing large oceanic resources are documented, there is little data on the consequences of use of traditional-FADs targeting spawning aggregations. In the eastern Arabian Sea, moored FADs composed of natural floating objects were designed and employed in isolated coastal rocky stretches to enhance small-scale artisanal fisheries. Recent increase in export demand for cuttlefishes has resulted in a renewed interest in extensive and unregulated use of FADs in cuttlefish fisheries transitioning from subsistence to market-oriented production. While the FAD-associated cuttlefish fishery has expanded rapidly by taking advantage of the spawning aggregation of the most abundant cuttlefish, Sepia pharaonis , there are many uncertainties with respect to the information on the characteristics of the exploited resource and the vulnerability of the spawning stock biomass (SSB) to fishing pressure. The biological characteristics of S. pharaonis exploited near FADs were compared with those of free-schools exploited by commercial trawling with respect to catch rates, size composition and reproductive status. We also assessed the impact of the aggregation-fishery on SSB and recruitment. Results suggested that the free-schools were assemblages of immature, maturing, spawning and spent individuals. On the other hand, the FADs aggregated larger spawning cuttlefish. Consequently, the annual spawning stock biomass (SSB) reduced from 17,862 t in 2008 to 1467 t in 2013. The number of recruits also reduced from 93.2 million in 2008 to 35.6 million in 2013. The occurrence of only gravid animals in FAD-associated fishery indicated that the cuttlefishes were attracted to the FADs for attaching their eggs. The analysis strongly suggested that (1) the spawning cuttlefish population is vulnerable to FAD-associated fishing; (2) the aggregation-fisheries harvested cuttlefish prior to spawning (high gonado-somatic index); (3) the removal of spawners having high reproductive value led to recruitment overfishing; and (4) aggregations may be more valuable when unexploited, as fishing on pre-spawning individuals can have adverse effects that go beyond the removal of biomass. As a sustainable management strategy, the FAD-based cuttlefish fishery was prohibited by the Fisheries Administration in 2012. [ABSTRACT FROM AUTHOR]

The use of dFADs by tuna purse-seine fisheries is widespread across oceans, and the echo-sounder buoys attached to these dFADs provide fishermen with estimates of tuna biomass aggregated to them. This information has potential for gaining insight into tuna behaviour and abundance, but has traditionally been difficult to process and use. The current study combines FAD logbook data, oceanographic data and echo-sounder buoy data to evaluate different Machine Learning models and establish a pipeline, named TUN-AI, for processing echo-sounder buoy data and estimating tuna biomass (in metric tons, t) at various levels of complexity: binary classification, ternary classification and regression. Models were trained and tested on over 5000 sets and over 6000 deployments. Of all the models evaluated, the best performing one uses a 3-day window of echo-sounder data, oceanographic data and position/time derived features. This model is able to estimate if tuna biomass was higher than 10 t or lower than 10 t with an F 1 -score of 0.925. When directly estimating tuna biomass, the best model (Gradient Boosting) has an error (MAE) of 21.6 t and a relative error (SMAPE) of 29.5%, when evaluated over sets. All models tested improved when enriched with oceanographic and position-derived features, highlighting the importance of these features when using echo-sounder buoy data. Potential applications of this methodology, and future improvements, are discussed. • Tun-AI is a model that is able to estimate the tuna biomass under a dFAD with ML algorithms trained on more than 12.000 set and deployment events. • ML algorithms are trained with echosounder data from dFADs and FAD-logbook data from the spanish fleet. • Our best model has a F1-score of 0.925 for binary classification and a relative error (SMAPE) of 29.5%, when evaluated only over set events. • A larger time window improves the accuracy of the prediction, at least up to 72 h, as circadian patterns in tuna schools become observable in the echosounder data. • Using oceanographic information and position-dependent derived features improves the accuracy of the prediction across all models. [ABSTRACT FROM AUTHOR]

Several empirical and theoretical studies have shown how the exploitation of food sources, the choice of resting sites or other types of collective decision-making in heterogeneous environments are facilitated and modulated by social interactions between conspecifics. It is well known that many pelagic fishes live in schools and that this form of gregarious behavior provides advantages in terms of food intake and predator avoidance efficiency. However, the influence of social behavior in the formation of aggregations by tuna under floating objects (FOBs) is poorly understood. In this work, we investigated the collective patterns generated by different theoretical models, which either include or exclude social interactions between conspecifics, in the presence of two aggregation sites. The resulting temporal dynamics and distributions of populations were compared to in situ observations of tuna behavior. Our work suggests that social interactions should be incorporated in aggregative behavior to reproduce the temporal patterns observed in the field at both the individual and the group level, challenging the common vision of tuna aggregations around FOBs. Our study argues for additional data to further demonstrate the role of social behavior in the dynamics of these fish aggregations. Understanding the interplay between environmental and social factors in the associative behavior of fish with FOBs is necessary to assess the consequences of the widespread deployment of artificial FOBs by fishermen. [ABSTRACT FROM AUTHOR]

Natural floating objects (e.g., logs) have always been a component of the habitat of tropical tunas. However, the introduction of fish aggregating devices ( FADs) modifies this environment. To assess the changes due to the deployment of FADs, we compared the spatial distribution of natural and artificial floating objects ( FADs), using data from observers onboard tuna purse seine vessels in the Indian Ocean from December 2006 to December 2008. Although natural objects occur more commonly in waters south of 7°S and FADs are more common in waters north of 7°S, all types of floating objects can be found everywhere. Using different spatial scales (quadrats of size 1° × 1°, 2° × 2°, 5° × 5°, and 10° × 10°), we computed the proportion of FADs observed in quadrats without natural objects. The scale of 2° × 2° quadrats represented a threshold: distributions of the two types of objects were different at scales smaller than this threshold. The strongest change that has occurred since the introduction of FADs (besides the increased catches) has been the dramatic increase in the total number of floating objects. Since the introduction of FADs, the number of objects has at least doubled everywhere (except in the Mozambique Channel and Chagos) and in some areas (e.g., Somalia area) the multiplication factor has reached as high as 20 or 40. Our study sets the ranges of values of key parameters of the floating object environment, which are crucial in the design of future experimental studies aimed at investigating the impacts of FADs on the ecology of tunas. [ABSTRACT FROM AUTHOR]

In the Western and Central Pacific Ocean (WCPO), which accounts for over half of world tuna production, purse seine effort and catch on floating objects have increased significantly due to a rapid increase in the use of fixed and free-floating fish aggregation devices (FADs). FAD fishing has had an impact on the current status of the stocks of the three main target tunas in the equatorial WCPO, skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares) and bigeye (T. obesus). FADs have been shown to influence the behaviour and movement patterns of the three tuna species with the juveniles of each species occupying shallower habitats when associated with FADs. Aggregation of tunas around drifting objects increases their vulnerability to purse seine gear, particularly for juvenile and small size classes. Further to the impacts on the target stocks, the use of FADs has increased the vulnerability of other fishes to the purse seine method, including some shark and billfish species. Given the concern over FAD-related fishing effort on target and bycatch species, there is a need to understand how FAD use affects target and bycatch stocks. Science needs to better support management decisions are highlighted including the need to identify the magnitude of broader community-level affects. [ABSTRACT FROM AUTHOR]

It is estimated that fish aggregating devices (FADs) are now used for over 40% of world tropical tuna catches, making this technique a major phenomenon for high seas fisheries worldwide, and one that has experienced great expansion over the past three decades. The question of whether the FAD is a good or a bad tool for the exploitation of marine resources depends on many parameters. To respond to this question, it is necessary to distinguish different scales of exploitation (artisanal vs. industrial) and various types of FADs (anchored vs. drifting), but it is also very important to gather more data and conduct further research on this topic to gain a better understanding of the phenomenon and of its impacts. As such, twelve years after the first international conference devoted to FADs, which was held in Martinique (French West Indies), a new multi-scalar global assessment of FAD fisheries development and a review of the progress of research in this field was deemed vital. The latest international conference, “Tuna Fisheries and Fish Aggregating Devices”, was held in Tahiti in November 2011, and it was an event that welcomed nearly 150 conference attendees from 40 different countries, three ocean regions, and the Mediterranean. This is an analysis of the relevant literature gathered by the author in the bibliographic database FADBASE. Then, the major issues already addressed by the scientific community are set out, and gaps and research priorities are highlighted for anchored and drifting FADs management. [ABSTRACT FROM AUTHOR]

Fish aggregating devices (FADs) used in the Gulf of Thailand are made of bamboo poles, twisted wire and coconut leaves, fastened to a concrete block. Purse seines with 2.5 cm mesh size are used to surround the fish, using fishing boats ranging from 18 to 26 m in overall length. Fishing grounds are located in the central Gulf of Thailand at a depth of 25–60 m. Catch per unit effort (CPUE), species composition and size of economically important species were analyzed by collecting data from fishing boats using FADs at nine main fishing ports along the Gulf of Thailand between January and December 2007. The results show that the average CPUE was 3351 kg day-1, which was composed of 88% pelagic fishes, 5% demersal fishes, 4% trash fishes and 2% squids and cuttlefishes. The major pelagic species were Indian mackerel (Rastrelliger kanagurta), Indian scad (Decapterus russelli) and bigeye scad (Selar crumenophthalmus), which made up 25%, 24% and 8% of the total catch, respectively, while neritic tunas (kawakawa; Euthynnus affinis, frigate tuna; Auxis thazard thazard and longtail tuna; Thunnus tonggol) made up 8% of the total catch. The mean length of ten economically important species was smaller than their size at first maturity, while two species were above their size at first maturity. The results indicated that juvenile fish were mostly being caught by FAD fishery, and this may lead to depletion in fisheries resources and economic loss. Although there is a set of measures to control the use of purse seines, effective management of the FAD capacity is also urgently needed. [ABSTRACT FROM AUTHOR]

The pole and line tuna fishery in the Maldives relies heavily on an array of 45 anchored fish aggregating devices (FADs), making it one of the largest anchored FAD-based tuna fisheries in the world. We examined the behaviour of skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares) tuna around anchored FADs (1 000 to 2 000 m deep) in the Maldives using passive acoustic telemetry. Eight neighbouring FADs (distance range: 30 to 95 km, average: 50 km) were equipped with automated acoustic receivers in January 2009, for a period of 13 months. A total of 40 skipjack (37−54 cm FL) and 21 yellowfin (35−53 cm FL) tuna were tagged with Vemco V13 transmitters in January (start of the northeast monsoon, dry season) and November (end of the southwest monsoon, wet season) 2009 and released at the two central FADs within this instrumented array. No movement between FADs was observed for any acoustically-tagged tuna in the instrumented FAD array. These results suggest that FADs in the Maldives may act independently. The maximum time a tagged skipjack remained associated with a FAD was 12.8 days in January but only one day in November. In addition, residence times at FADs were found to differ with time (month) and space (FAD location) for skipjack tuna, suggesting that external biotic factors (e.g., prey, conspecifics or predators) might influence the time this species spends at FADs. In November, the residence times of yellowfin tuna (maximum observed time: 2.8 days) were three times greater than those of skipjack tuna at the same FADs. This specific difference could be explained either by the two species responding to different factors or by the species’ responses being dependent on the same factor but with different thresholds. No particular preference for time of departure from the FADs was observed. Some monospecific and multispecific pairs of acoustically-tagged individuals were observed leaving the FADs simultaneously. Thus, this study indicates a high degree of complexity in the behavioural processes driving FAD associations. [ABSTRACT FROM AUTHOR]

Abstract: Identifying spatial and temporal patterns in fish movements can reveal the driving factors that govern the behavior of fish in their environment. In this study, we characterized the spatial and temporal occupation of 37 acoustically tagged bigeye scads (Selar crumenophthalmus) in an array of shallow Fish Aggregating Devices (FADs) to clarify the mechanism that leads fish to associate with FADs. A comparison of the number of visits and residence times exhibited by the fish at different FADs revealed a strong variability over the array of FADS, with the emergence of a leading FAD that recorded the majority of visits and retained the fish for a longer period of time. We found diel variability in the residence times, with fish associated at daytime and exploring the array of FADs at nighttime. We demonstrated that this diel temporal pattern was amplified in the leading FAD. We identified a 24-hour periodicity for a subset of individuals associated to the leading FAD, thus suggesting that those fish were able to find this FAD after night excursions. The modeling of fish movements based on a Monte Carlo sampling of inter-FAD transitions revealed that the observed spatial heterogeneity in the number of visits could not be explained through simple array-connectivity arguments. Similarly, we demonstrated that the high residence times recorded at the leading FAD were not due to the spatial arrangement of individual fish having different associative characters. We discussed the relationships between these patterns of association with the FADs, the exploration of the FAD array and the possible effects of social interactions and environmental factors. [Copyright &y& Elsevier]