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Ecosystems and biodiversity across the world are being altered by human activities. Habitat modification and degradation is among the most important drivers of biodiversity loss. These modifications can have an impact on species behavior, which can in turn impact their mortality. With around 5 million tons fished yearly, tuna species represent more than 7 % of global marine fish capture, of which two third are captured by purse seine vessels. Because several pelagic fish species, such as tuna, associate with floating objects, fishers have started deploying their own floating objects – Drifting Fish Aggregating Devices (DFADs) – in the early 1990s to increase tuna catchability. Since then, the massive deployment of DFADs has modified tuna habitat, by increasing the density of floating objects, with potential consequences on tuna associative behavior. This use of DFADs by purse seine fisheries is a major concern and it offers an important case study to assess the impact of habitat modifications on species behavior and mortality. In this study we use an individual-based model, based on a correlated random walk calibrated on passive acoustic tagging data, to determine a general relationship between DFAD density and the time tuna spend between two associations with a DFAD. Using this general relationship and fisheries data in the Indian Ocean, we predict that the increase of floating object density, due to DFAD use, strongly increases the percentage of time tuna spend associated, which directly impacts tuna availability to fishers and fishing mortality. This modification of tuna associative behavior could also have indirect impacts on their fitness, by retaining tuna in areas detrimental to them or disrupting schooling behavior. Hence, there is an urgent need to further investigate DFAD impacts on tuna behavior, in particular taking social behavior into account, and to continue regulation efforts on DFAD use and deployments.

This research is motivated by a contradictory reality about the life of traditional fishermen. Traditional fishermen have “sacred” zones for fishing activities which are protected by law due to their highest biodiversity and cultural importance to local fishing communities. On the other hand, 76 percent of the traditional fishermen are classified as poor; the level of poverty headcount index (PHI) reaches 32.4 percent. Based on this contradictory situation, 2 (two) important questions arise: what happens in the fishing area of traditional fishermen and whether the poverty experienced by traditional fishermen starst from this fishing ground. This research took place in Bagan Kuala, a village where the majority of the population are traditional fishermen. This study used an ethnographic approach with two data collection tools, which are interviews and observations. It was found that each traditional fisherman in this village has its own fishing grounds and boundaries. The boundary is marked by fish aggregating device (FAD), which also serve its purpose as fish catcher. Some of the FADs have been owned by fishermen for many generations. Outsiders often trespass this fishing ground, particularly at night where they use modern tools like trawl, destroying the fishermen’s FADs. As a result, there are conflicts and also negotiations involving the locals and outsiders who asked for their permission; the catch was divided depending on the agreement. From these findings, it can be concluded that poverty can start from the fishing ground.

Drifting Fish Aggregating Devices (dFADs) are a major fishing mode for tropical tuna purse seine fisheries worldwide. However, the extent of dFAD use remains poorly understood. We present novel approaches for estimating annual dFAD deployments and number of dFADs monitored by individual vessels, using empirical data and robust estimation procedures. We leveraged observer and logbook data, combined with new dFAD tracking data from the Western and Central Pacific Ocean (WCPO) purse seine fishery, the largest tuna fishery in the world, to evaluate trends in dFAD use across the entire WCPO between 2011 and 2019. Average estimates ranged between 20 000 and 40 000 deployments per year, depending on the methodology, with the total number of deployments appearing relatively stable over the last decade. The median number of active buoys monitored per vessel per day ranged from 45 to 75 depending on the year, well below the current management limit of 350. Our results contrast with other oceans, having fewer buoys monitored per vessel, a unique stable trend, but overall number of deployments two times higher than any other ocean. This study provides a basis for improved monitoring and management of dFAD use in the WCPO, with applicability for other regions.

For centuries fishers have exploited the propensity for tuna to associate with floating objects, yet the reasons and mechanisms behind this behavior remain unclear. The number of man-made floating objects (FADs, Fish Aggregating Devices) undergone a dramatic increase in recent decades, with the development of industrial tuna purse seine fishing. However, current knowledge does not allow for the evaluation of the consequences of this increase on the ecology of tuna. Here, we developed a model of tuna movements in an array of FADs, using passive acoustic tagging data. The model was built using four behavioral rules: (1) when no FAD is perceived, tuna exhibit a random search behavior, (2) individuals can orient directly to a FAD when they perceive it (within a given orientation radius), (3) the associative dynamics of tuna follow a daily rhythm and (4) Continuous Residence Time (CRTs – time spend at FAD by tuna) are independent from previous Continuous Absent Time (CATs- time between two consecutive CRTs). The model is based on only four parameters: swimming speed, path sinuosity, orientation distance and a loss term to account for natural and fishing mortality events. The model was calibrated on 70±10 cm yellowfin tuna (Thunnus albacares), acoustically tagged in two different networks of anchored FADs (Oahu, Hawaii, U.S.A. and Mauritius) with different FAD densities. Our results show that the model can reproduce the time tuna spent traveling between FADs (i.e., time away from the FADs), as well as the total time spent by the fish in the FAD array (total residence time) at both study sites. The parameter sets that best reproduce the experimental data correspond to a steering radius between 2 and 5 km, a sinuosity (correlated random walk parameter) between 0.9 and 0.995 and mortality rates between 1 and 3% per day. This model, thus parameterized, could be used in future studies to predict tuna movements in arrays of different FAD densities and thus provide scientific advice for their management. The same approach can be used for modeling the movements of marine and terrestrial animals detected near aggregation sites.

Indonesia has many archipelagos with long and complex coastlines that connect to the Pacific Ocean in the northeast and to the Indian Ocean in the southwest. Several species of fish in this area are easily attracted to fish aggregating devices (FADs), which are a type of environmentally friendly artificial ocean infrastructures. We investigated characteristics of tidal currents in the Indonesia archipelagos and suitably designed a small-scale tidal-current turbine with an FAD to independently supply electric power to the archipelagos. Moreover, we estimated the amount of electric power generated by the setup. The results indicate that the tidal currents in narrow straits are considerably higher in archipelagos, such as the Maluku and Nusa Tenggara Islands including Bali Strait. Lombok Strait also exhibited the maximum tidal-current velocity of 4 m/s. The small-scale tidal-current turbine was theoretically and numerically designed to utilize the tidal current specific to the Indonesian archipelagos. We estimated the amount of electric power generated by the 2.2-m-diameter turbine with 10-kW class to adjust to the specific archipelagos.

The aims of this study were to compare skipjack catch between FAD and free school fishing grounds and to describe the effect of the oceanographic factors on either skipjack tuna Fish Aggregating Device (FAD) or free school. We used a field survey method for collecting the skipjack catch and the fishing positions for both near FAD and free school areas. Remotely sensed satellite data of sea surface temperature (SST) and chlorophyll-a concentration (Chl-a) were also used to extract the oceanographic data corresponding with both the fishing locations. To find out the vital oceanographic factors, we examined the characteristics of the oceanographic variables and skipjack catch using t-test. Results indicated that the fishing operations of skipjack tuna at FAD tended to locate areas of relatively higher Chl-a than at free school locations. We also found that skipjack tuna catch was higher near the FAD than the other area, where the Chl-a was the most significant factor that affected the difference. This study suggests that the number of skipjack tuna FAD in the coastal waters of Bone Bay should be calculated accurately to ensure and support the tuna fishing management in that study area.

As for several dozen other marine species, tropical tunas show an association behavior with floating objects. These objects can come from plant debris (coconuts, logs, etc.) or human pollution. Others are deliberately constructed by humans and deployed on the high seas or fixed on the seabed close to the coast, with the aim of aggregating tuna in support of fishing activity. The latter are called Fish Aggregating Devices (FADs). Despite the large increase in the number of FADs deployed in all oceans, no study has yet been able to quantify the impact of the addition of FADs on the ecology of tropical tuna, while the majority of their catches take place currently at FADs. The general objective of this thesis is to study the impact of the increase in the number of FADs on the behavior of tuna.For the first time, through passive acoustic tracking data of tropical tunas, it has been shown that travel times between two FADs decrease with increasing FAD density, due to random search behavior. On the contrary, the association time with each floating object increases with the increase of FAD density, which can be explained by a role of social behavior and/or the prey environment. The knowledge gained from the acoustic tagging experiments has allowed the development of a model capable of reproducing the movements of tuna in a FAD array. This simple but robust model is based on three behavioural rules (correlated random walk dynamics, ability of tuna to orient themselves towards a FAD and diel tuna behavior) and four parameters (swimming speed, path sinuosity, orientation radius and mortality rate). The application of this model allowed for the first time to highlight the impact of the increase in FAD density on the movement patterns of tuna in a FAD array. This model offers a predictive tool to evaluate the increase in catchability of tuna due to the increase in FAD density, in the case of drifting or anchored FAD networks. More generally, this thesis provides first quantitative means to evaluate the impacts of FADs on the ecology of tuna.; De même que plusieurs dizaines d’autres espèces marines, les thons tropicaux présentent un comportement d’association avec les objets flottants. Ces objets peuvent provenir de débris végétaux (noix de coco, rondin de bois, etc.) ou de la pollution humaine. D’autres sont volontairement construits par l’humain et déployés en haute mer ou fixés sur les fonds océaniques proches de la côte, dans le but d’agréger des thons en soutien à l’activité de pêche. Ces derniers sont nommés Dispositifs de Concentration de Poissons (DCP). Malgré la forte augmentation du nombre de DCP déployés dans tous les océans, aucune étude n’a encore pu quantifier l’impact de l’ajout de DCP sur l’écologie des thons tropicaux, alors que la majorité de leur captures se font actuellement sous DCP. L’objectif général de cette thèse est d’étudier l’impact de l’augmentation du nombre de DCP sur le comportement des thons. Pour la première fois, à travers des données de suivi acoustique passif de thons tropicaux, il a été mis en évidence que les temps de trajet entre deux DCP diminuent avec l’augmentation de la densité de DCP, s’expliquant par un comportement de recherche aléatoire. Au contraire, les temps d’associations à chaque objet flottant augmentent avec l’augmentation de la densité de DCP, s’expliquant par un rôle du comportement social et/ou de l’environnement en proies. Les connaissances issues des expériences de marquage acoustique ont permis de développer un modèle capable de reproduire les déplacements des thons dans un réseau de DCP. Ce modèle simple mais robuste se base sur trois règles de comportement (une dynamique de marche aléatoire corrélée, une capacité d’orientation des thons vers un DCP et un comportement cyclique journalier) et quatre paramètres (vitesse de nage, sinuosité du trajet, rayon d’orientation et taux de mortalité). L’application de ce modèle a permis pour la première fois de mettre en évidence l’impact de l’augmentation de la densité de DCP sur les schémas de déplacement des thons dans un réseau de DCP. Ce modèle offre ainsi un outil prédictif pour évaluer l’augmentation de la capturabilité des thons due à l’augmentation de la densité de DCP, dans le cadre de réseaux de DCP dérivants ou ancrés. Plus généralement, cette thèse fournit des premiers moyens quantitatifs pour évaluer les impacts des DCP sur l'écologie des thons.

The silky shark Carcharhinus falciformis regularly associates with floating objects in the open ocean, resulting in relatively high levels of bycatch in industrial tuna purse seine fisheries using drifting fish aggregating devices (FADs). This bycatch has contributed to concerns regarding the sustainability of this fishery and its impact on silky shark populations. To investigate fishery interactions, movements of 28 silky sharks (86–235 cm TL, mean = 118 cm) fitted with pop-up and archival tags in the western Indian Ocean, between 2010 and 2012, were examined. Monthly overlap between probability surfaces of sharks and two fishery metrics (FAD-tuna catches and FAD positions) were calculated. Vertical habitat use overlapped almost entirely with operational gear depth. Horizontal movements were extensive (3–5024 km) and covered large areas of the western Indian Ocean. Monthly overlap with FAD distributions was consistently high (64.03–100%) highlighting the need for compliance with FAD design regulations to avoid entanglement. Monthly overlap with tuna catches was more variable (8.43–51.83%). The observed movement patterns suggest static spatial management measures would be have limited conservation impact, however dynamic approaches could be appropriate. Limiting fishery activities directly will likely have the greatest conservation outcomes for silky sharks in the purse seine fishery.

Different fishing strategies have been adopted in the last decades by tropical tuna purse seiners fleet, including fish aggregating device (FAD) and free-swimming school (FSC) fishing strategies, which has raised issues about the different carbon footprint of those fishing modes. Here we show the activity and energy patterns of a Spanish tuna purse seiner operating in the tropical Indian Ocean, based on the monitoring of energy consumption over 10 consecutive fishing trips; and we also assess the fuel use intensity of FAD versus FSC fishing by analysing 14 further trips of different tropical tuna purse seiners. The average time of a fishing trip lasted 33.1±11 days. The dominant activity during the fishing trip was cruising (with 68.5% of the time), followed by inactive period at sea (15.6%), fishing (7.7%), and in port (8.1%). The vessel consumed 381±113 t fuel/trip, of which 90.4% was spent in cruising, 4.3% in fishing, 3.7% during the inactive period at night and 1.6% while staying in port. The main engine consumed 75% of the total fuel, while the auxiliary engines the remaining 25%. Furthermore, our results demonstrated that FAD fishing (543.6 L/t) is more fuel intensive, than FSC fishing (439.4 L/t). However, FADs fishing successful rates are higher, around 95.7±3.8%, than FSC rates (around 80.6%±5.8). It is worth noting that the differences may be driven by seasonality and FSC availability, number of FADs in an area, vessel characteristics and equipment, and skipper skills rather than the adopted fishing strategy. Nonetheless both FAD and FSC fishing are more energy efficient than longline (1069 L/t), trolling (1107 L/t), or pole and line (1490 L/t) fisheries for Atlantic tuna, but similar or slightly less efficient than Maldivian pole and liners.

Incidental capture of juvenile bigeye tuna in fish aggregating device (FAD)-associated purse seine fisheries targeting skipjack tuna have contributed significantly to the degradation of bigeye stocks in the Western Tropical Pacific (WTP) Ocean. One way to reduce this incidental catch is to simply limit purse seine fishing effort; however, skipjack tuna stocks are healthy and economically important to many small island nations in the region. Here we assess whether there is sufficient lateral separation of skipjack and bigeye within FAD-associated purse seine fisheries in the WTP to allow limiting bigeye catch while maintaining a robust skipjack fishery. Based on monthly 5°-longitude-by-5°-latitude catch and effort data, FAD-associated bigeye and skipjack catch per unit effort (CPUE) covary tightly throughout the WTP, such that lateral separation between the two species is generally small. There are, however, significant variations in the amount of separation over both space and time. Waters within the Party to the Nauru Agreement exclusive economic zones (EEZs) belonging to Palau, Solomon Islands, and Tuvalu regularly exhibit some of the smallest bigeye-to-skipjack catch ratios, especially during El Niño. In contrast, waters within Kiribati’s Phoenix Islands EEZ regularly exhibit some of the largest bigeye-to-skipjack catch ratios, which are particularly high during La Niña. In general, El Niño lowers bigeye-to-skipjack catch ratios east of 170°E, while La Niña lowers bigeye-to-skipjack catch ratios west of 170°E. These ENSO-driven variations in separability are larger and more widespread than those driven by seasonality, due to larger associated variations in environmental conditions. Sea surface height anomalies may be particularly useful for demarcating the different environments preferred by skipjack and bigeye throughout the WTP. Sea surface temperatures, temperatures at 100 m, and thermocline depths may also help distinguish between the two species’ preferred habitats in many areas. These analyses can help better inform the complex decisions made by both fishers during operations and fisheries managers during creation of effective, dynamic policies to preserve bigeye stocks in the WTP. They also show that climate variability can have substantial effects on the spatial distributions of top pelagic predators and their interactions with one another.

Place: Oxford Publisher: Pergamon-Elsevier Science Ltd WOS:000582696800013; International audience; In the Tropical Atlantic Ocean, we assessed the accuracy of a Lagrangian model (Ichthyop) forced with velocity fields from a hydrodynamical model (CROCO) and two different remote sensing products (GlobCurrent and OSCAR) using trajectories of oceanographic drifters. Additionally, we evaluated the possibility to expand the drifters data using trajectories of GPS-buoy equipped drifting Fish Aggregating Devices (FADs). The observed and simulated trajectories were compared in terms of spatial distribution, velocity distribution and a nondimensional skill score. For the drifters and FADs, the GlobCurrent and OSCAR products lead to similar performances as the CROCO model-ouputs in the broad studied domain. In the Gulf of Guinea, however, the CROCO model performed significantly better than the other two because the parent solution of CROCO benefited from its communication with a child grid of finer resolution in this region. On average, the simulations lead to an underestimation of the drifter and FAD velocities, likely because the spatial resolutions of the forcing products were insufficient and the time frequency at which they were produced were too low to resolve the relevant oceanic processes properly. We found a low skill for all models to simulate FAD trajectories, possibly because of the devices vertical structure that prevent FADs from drifting like water parcels. Our results therefore suggest that in the Tropical Atlantic the FAD dataset may not be appropriate to use for corroborating Lagrangian simulations.

Sinkable fish aggregating devices (FADs) are used in the waters around Japan. These FADs are designed to submerge when sea currents are fast and to float at the sea surface when currents are slow. However, concerns have been raised about the effect of sinkable FADs on fisheries. We investigated the sinking dynamics of sinkable surface-type FADs and examined the behavior of a migratory fish species using an ultrasonic biotelemetry system to clarify the effects of the FAD sinking on fish behavior. The investigation was conducted in the waters around Yonaguni Island, Okinawa, Japan. Receivers and depth sensors were installed on two sinkable surface-type FADs and one simple surface-type FAD. In addition, transmitters were attached to 17 skipjack tuna which were released around the FADs. The results showed that there was no relationship between the timing of FAD sinking and fish leaving the FAD. Further, FADs dynamics did not decrease the fish attraction ability of FADs. Over the course of the study, the swimming depth in migrating fish was deeper at night than it was during the day. No relationship was observed between daily fish behavior and FAD sinking, but observations of FAD dynamics revealed that high current velocities (>2.5 kn) were more frequent at night. The observation of deeper swimming depth at night was suggested to be related to high current velocities at the surface. Fish were not observed to surface, even during twilight hours, when current velocities were high and when FAD sinking continued for more than a day. The vertical distance between two individuals staying at the FAD tended to increase during single-sinking (SS; i.e., when FAD was single sinking and surfacing) or at night when SS occurred. During continuous-sinking (CS; i.e., when FAD was repeated sinking and surfacing below the sea surface), the vertical distance between individuals increased after the floating body started sinking and the vertical distance between individuals exceeded 60 m, but decreased to less than 20 m after several hours. The vertical distance between fish during CS decreased at night, sometimes coming within 1 m of each other, suggesting that the fish were trying to maintain a school around the FADs.

Rumpon laut dangkal sebagai alat bantu dalam penangkapan ikan di perairan sekitar Pasauran, Selat Sunda telah lama dan semakin banyak digunakan di Indonesia untuk menangkap ikan pelagis. Karakteristik komposisi jenis, ukuran dan Tingkat Kematangan Gonad (TKG) ikan pelagis yang tertangkap di sekitar rumpon dengan menggunakan tiga bahan atraktor yang berbeda yaitu daun kelapa (Cocos nucifera), daun pinang (Nypa fructican) dan daun nipah (Areca catechu) akan menentukan apakah pengaruh bahan atraktor yang digunakan akan membahayakan kelestarian ikan pelagis yang berasosiasi. Identifikasi dan komposisi panjang, berat dan TKG ikan pelagis dilakukan dengan menggunakan bahan atraktor yang berbeda pada setiap musim dalam penelitian ini. Experimental fishing dilakukan dengan menggunakan alat tangkap payang Bugis. Hasil pengamatan menunjukkan bahwa atraktor daun kelapa merupakan bahan atraktor yang terbaik yang dapat digunakan sebagai atraktor pada rumpon dilihat dari hasil tangkapan serta daya tahan di suatu perairan pada setiap musim. TKG ikan pelagis kecil yang tertangkap di sekitar rumpon memiliki TKG I 4%, TKG II 33%, TKG III 35%, TKG IV 25% dan TKG V 3%. Ikan hasil tangkapan di sekitar rumpon dengan bahan atraktor yang berbeda memiliki TKG I-III sebesar 72% sehingga dapat dipastikan bahwa ikan-ikan yang berkumpul dan tertangkap di sekitar rumpon adalah ikan yang belum memijah atau belum dewasa, sehingga ikan tersebut tidak sempat melakukan reproduksi

Seventeen members and cooperating non-members (CCMs) of the Western and Central Pacific Fisheries Commission (WCPFC) were responsible for 86% of the total catch of bigeye tuna Thunnus obesus by purse seine fishing from 2012 to 2014. We categorize the CCMs into an eastern, western and “other” group based on their main fishing areas. We found significant differences in the bigeye tuna catch per fish aggregating device (FAD) between the eastern group and the western group. We also estimated that the eastern group achieved a higher catch of bigeye tuna because of their increased fishing effort using FAD in the eastern area where there is a higher catch per unit effort for FAD. The regression analysis found significant correlations between the annual catch of bigeye tuna and the number of FAD sets. The average catch of bigeye tuna per single FAD set, estimated from the slope of the regression line, was 7.1 t in the eastern area and 2.7 t in the western area. An impact and risk plot composed of the slope of the regression line and the catch of bigeye tuna by each individual CCM was developed to improve management measures. Appropriate measures for the sustainable use of tuna resources in the region are discussed.

The increased use of drifting Fish Aggregating Devices (dFADs) by tuna purse seine fleets in recent years has supported considerable catches of these species. A greater understanding of the spatiotemporal dynamics of these objects as they drift with ocean currents is critical for understanding historical changes in fishing power, spatial management, and examining the effect of ambient dFAD density on catch and effort. Here, dFAD dynamics were estimated for all floating object sets made by purse seiners in the Western and Central Pacific Ocean during 2016 and 2017. The drift trajectories of these floating objects prior to the observed fishing events were estimated by seeding virtual Lagrangian particles within a state-of-the-art hydrodynamics model, and simulating their movements backwards in time. Resulting trajectory distributions are similar to observed dFAD trajectories from the same period. The approach provides spatial density estimates in areas where observed dFAD data are incomplete, particularly in the exclusive economic zone (EEZ) of Howland and Baker Islands, and certain high seas areas. We provide estimates of inter-EEZ connectivity of dFADs, which highlight the fact that dFADs set upon in small EEZs such as Nauru and Howland and Baker Islands are likely to have drifted from neighbouring EEZs less than one month prior to fishing. dFADs typically transited multiple EEZs, with a median of 4 and a maximum of 14, when assuming a drift-time of six months. Moreover, between 4 and 22% of dFAD sets made in the WCPO were estimated to have originated from the Eastern Pacific Ocean, depending on drift-time. We examine our results in the context of the improved management and assessment of dFAD fisheries, providing a methodology to estimated relative dFAD density over historical periods to support analyses of catch and effort. The sensitivity of these estimates to hydrodynamic models, including the proposed SKIM doppler radar altimetry method, is discussed.

Knowledge of ocean surface dynamics is crucial for oceanographic and climate research. The satellite-tracked movements of hundreds of drifters deployed by research and voluntary observing vessels provide high-frequency and high-resolution information on near-surface currents around the globe. Consequently, they constitute a major component of the Global Ocean Observing System (GOOS). However, maintaining this array is costly and in some oceanic regions such as the tropics, spatio-temporal coverage is limited. Here, we demonstrate that the GPS-buoy equipped fish aggregating devices (FADs) used in tropical tuna fisheries to increase fish catchability are also capable of providing comparable near-surface current information. We analyzed millions of position data collected between 2008 and 2014 from more than 15,000 FADs and 2,000 drifters, and combined this information with remotely-sensed near-surface current data to demonstrate that the surface velocity components of FADs and drifters are highly correlated in the Atlantic and Indian Oceans. While it was noted that the subsurface structures of FADs (typically made of recycled fishing nets) did slow them down relative to the drifters, particularly in the Atlantic Ocean, this bias was measurable and could be accounted for in future studies. Our findings show that the physical meteorological and oceanographic data collected by fishermen could provide an invaluable source of information to the GOOS. Furthermore, by forging closer collaborations with the fishing industry and ensuring their contributions to global ocean databases are properly acknowledged, there is significant scope to capture this data more effectively.

An at-sea experiment was undertaken to evaluate the performance of 150 shallow depth (5 m) prototype drifting fish-aggregating devices (DFADs) with rope appendages, compared to 150 standard depth (∼ 40 m) traditional design DFADs with purse-seine net appendages, in the equatorial eastern Pacific Ocean tuna purse-seine fishery, seeking a solution to reduce purse-seine fishing mortality on undesirable sizes of bigeye tuna. Following concurrent deployments of the two DFAD types along transects, the average daily drift speeds were significantly different but similar as were the drift trajectories among the two DFAD types. Based on evaluations of the time-series of acoustic data from the echo-sounder buoys attached to the shallow and standard depth DFADs, the average time before aggregation by non-tuna species was 15.3 d (range: 3.2–65.5) and 18.2 d (range: 1.1–101.2), respectively, and the average time before aggregation by tuna species was 62.2 d (range: 3.3–248.3) and 70.2 d (range: 1.5–270.5), respectively. Analyses of the catch per set data for tunas and non-tuna species, using generalized additive mixed models with Bayesian inference, indicated no significant differences in catch rates from sets on shallow and standard depth DFADs. There was a similar proportion of bigeye tuna in the catch for purse-seine sets on the shallow and standard depth DFADs.

Moored fish aggregating devices (MFADs) are promoted throughout global small-scale fisheries as tools to enhance livelihoods and shift fishing pressure onto offshore resources. A particularly large number of projects initiating and encouraging MFAD development have occurred in the Caribbean region. Despite ongoing promotion of MFAD fisheries in the region, there is limited understanding of their current extent, distribution, and management across Caribbean states. Here we integrate key informant surveys with a supporting literature review to generate the first comprehensive overview of MFAD fishery status and trends in the insular Caribbean and Bermuda. While regional growth has been substantial, we find wide diversity among states in terms of the number of MFADs deployed, MFAD ownership (private or public), fleet engagement, and the existence and enforcement of MFAD regulations. Our results suggest that despite the presence of regulations in some states, management limitations and private MFAD ownership may be associated with a rapid proliferation of deployed MFADs across the Caribbean. We discuss the critical role of management and monitoring in attaining the anticipated benefits of MFAD fisheries and reducing social and environmental risks. By documenting the diverse paths that MFAD fisheries have taken in different states, this study provides an opportunity for prospective and existing MFAD programs to better evaluate the risks and rewards associated with MFADs and to design appropriate management.

A study was carried out to assess the ecological aspects of Balla beel ecosystem in Moulavibazar district and the affectivity of the ongoing biodiversity restoration program from July 2011 to June 2012. Seventy-four fish species belonging to 21 families were identified during the study period. About nine types of fishing methods and one type of fish aggregating device were identified in the surveyed beel. Increasing pressure of illegal current jal (gill net), ber jal (seine net) and FAD (Fish Aggregating Device) was detected as the reduction of almost all type of species. About 24 aquatic weeds were found in the Balla beel, among them both emergent and spreading were 29%, followed by floating 21%, 13% were rooted plants with floating leaves and 8% were submerged. The dissolved oxygen content 5.22±1.60 mg/l inside and 5.70±1.38 mg/l outside of the Balla beel sanctuary were found to be congenial for aquatic life. pH of the beel water both inside and outside of the sanctuary were slightly acidic to moderately alkaline (7.0±0.68 inside and 6.88±0.43 outside the sanctuary). Lower values of alkalinity and hardness indicating beel water to be less nutrient enriched. The contribution of phytoplankton (79%) was larger than zooplankton (21%). The diversity of phytoplankton both inside and outside of the sanctuary was dominated by three group Chlorophyceae, Myxophyceae and Bacillariophyceae.Asian J. Med. Biol. Res. June 2015, 1(2): 198-208

Seaweed development has had positive impacts on surrounding environments and fisheries resources, even using traditional technologies. The integration of aquaculture and capture fisheries will have a multiplier effect on fish farmer income as well as supporting the development of the aquaculture sector. This research aimed to optimize the utilization of fisheries resources around seaweed culture areas. Two case studies were conducted at Libukang Island, Jeneponto District, South Sulawesi, and at Sarudu village, North Mamuju District, West Sulawesi. Resource use in seaweed culture areas was optimized through the design, construction, and implementation of improved fishing gears: gill nets, bamboo traps, and fyke nets. The study results show that integrating seaweed culture and capture fisheries using these gears can increase fishermen’s incomes. The level of additional income depends on fishing intensity. In addition, seaweed culture productivity should be improved through integration with fish cage culture. The cultured fish expel waste to the environment (feed, feces, and urine) that can provide nutrients to the seaweed. The sustainability of fishing depends so much on the sustainability of seaweed culture were used as a fish aggregating device.

The research was conducted to investigate the oceanographic characteristics at three traditional anchored Fish Aggregating Device (FADs) sites for tuna pole-and-line fishery in eastern Indonesia. The FADs locations, and sea surface temperature (SST) and chlorophyll-a (chl-a), salinity (sal), wave height (wav), wind (win) current (cur) were examined using a geographic information system (GIS). Relationships between Catch-per-Trip (CPT) with oceanographic characteristics (SST, chl-a, sal, wav, win and cur), were analysed using correlation and generalised additive models (GAMs) analyses. Correlation analyses was used in order to determine how strongly pairs of variables were related to one another, and generalised additive models (GAMs) were used in order to model relationships between Catch-per-Trip (response variable) and the oceanographic variables SST, chl-a, sal, wav, win and cur (predictor variables). Correlation analyses showed that significantly negative correlations were found in entire locations between SST and chl-a while in contrarily, the lowest correlation was found between CPT and chl-a. Furthermore, the GAM plots indicated that a positive association was observed between catch-per-trip and SST with approximately >26.5 °C, chl-a was 33 to 0.23 for Sorong and >0,87 (m) in Larantuka and 4.1 m/s in entire research sites while cur had a positive effect on CPT occurred at

Fish aggregating device (FAD) are commonly used in Indonesia and once deployed in the waters they are immobile. A portable FAD equipped with sound generating devices is an innovation to attract fish which has capability to react to audio stimulant. A fishing trial in April 2019 was carried out to check the performance of the EFAD. The research was carried out using a research vessel operating handlines with fish baits. The fishing trial successfully caught the white spotted triggerfish (Canthidermis maculatus), which is usually bycatch of tuna purse seine and gillnet fisheries. The catch of the trigger fish could not be attributed solely to the sound generated by EFAD because other factors, such as the fish bait and the size of the boat, might attract the fish.

Reservoirs have been given priority as an important resource for fisheries enhancement in inland open waters. This paper described the spatial and temporal pattern of fish diversity using GIS platform, assemblage structure, and studied the influence of environmental parameters in these variables in a large tropical reservoir, Chandil, located in the eastern India using multiple approaches. Altogether, 42 fish species belonging to 30 genera were recorded from the reservoir, including two exotic species: pangas, Pangasianodon hypophthalmus, and Nile tilapia, Oreochromis niloticus. The diversity indices indicated lowest fish diversity in the lacustrine zone, but without distinct seasonal variation. The taxonomic distinctness was lower in the lacustrine zone as compared to other zones, and the summer season exhibited higher taxonomic distinctness, though the number of species was lowest. Most of the physicochemical parameters recorded are within the favorable range for fisheries enhancement. Among the environmental parameters, pH and nitrate significantly influenced the fish abundance. The study recommends suitable measures and interventions for conservation of the native fish diversity and sustainable fisheries development: closed season, protected/conservation area, introduction of fish aggregating device (FAD), and regulated fish culture in enclosures.

Tuna exploitation in the Banda Sea was started when the Indonesian government gave access to the Japanese fleet under the bilateral cooperation of the Banda Sea Agreement (BSA) in 1975-1980. Several studies were conducted afterward in revealing the magnitude of tuna resources in the Banda Sea. In this paper, we reviewed the tuna studies that were done in the Banda Sea over the periods of 1980-2017 to improve our understanding on the biology and ecology of tuna in the region as the basis for future studies. Overall, we reviewed 29 publications consisted of eight research themes; biodiversity (5), catch composition (8), fish aggregating device (FAD) (2), fishing ground (2), growth-population (3), harvest-effort strategy (4), reproduction (4), and tagging (1). The Snellius II expedition in 1984-1985 was a remarkable study covering almost whole area of the Banda Sea. The study of catch composition and biodiversity were dominant in recent decade indicating there was urgent need to manage the tuna fisheries in the Banda Sea to preserve the tuna stock. Since the Banda Sea is considered as a tuna conservation area, the future studies should be focussed on the scientific findings to support the regulation.

Fish Aggregating Device (FAD) usually used by small and large scale fishermen in Indonesia are FAD shallow and deep sea water which fix in the water. Effectiveness and efficiency research activity about portable FAD in the water to catch Thunnus spp. and skipjack have never been done in Indonesia. This research divided into two stages : portable FAD design, fishing trial with portable FAD used handline and troll line in Palabuhanratu waters. The purpose of this research was to make portable FAD design, fishing trial used Electric Fish Attractor (EFA) with different frequency and to compared effectiveness of catch composition with handline and troll line. The result of this study were design FAD portable with length and width 1 m, the material is manglid wood, the attractors are raffia line and attractor and sinker line used PE with diameter 4 mm and tin sinker, EFA with frequency 10-1.000 Hz catch Caranx fasciatus and Trichiurus sp., whereas EFA with frequency 1.000-20.000 Hz catch 2 fish of Thunnus albacares with length 30 cm and weight 40 kg, catch composition used handline was Trichiurus sp. 63%, Nemiptarus sp. 10%, Caesio cuning 7%, Euthynnus spp. and semar 4%, Lutjanus spp. and Thunnus albacares 2%, whereas catch composition with troll line was Rastrelliger spp, Caesio cuning, and Selaroides spp. 1%.

Juvenile silky sharks Carcharhinus falciformis comprise the largest component of the incidental elasmobranch catch taken in tropical tuna purse seine fisheries. During a chartered cruise on board a tuna purse seine vessel conducting typical fishing operations we investigated the post-release survival and rates of interaction with fishing gear of incidentally captured silky sharks using a combination of satellite linked pop-up tags and blood chemistry analysis. To identify trends in survival probability and the point in the fishing interaction when sharks sustain the injuries that lead to mortality, sharks were sampled during every stage of the fishing procedure. The total mortality rates of silky sharks captured in purse seine gear was found to exceed 84%. We found survival to precipitously decline once the silky sharks had been confined in the sack portion of the net just prior to loading. Additionally, shark interactions recorded by the scientists were markedly higher than those recorded by vessel officers and the fishery observer. Future efforts to reduce the impact of purse seine fishing on silky shark populations should be focused on avoidance or releasing sharks while they are still free swimming.

We used global positioning system (GPS) technology and tracking analysis to measure fishing effort by marine, small-scale, fish aggregating device (FAD) fishers of the Commonwealth of Dominica. FADs are human-made structures designed to float on the surface of the water and attract fish. They are also prone to common pool resource problems. To identify free riders with respect to specific FADs, we need to compare the cost expended for FAD construction versus the benefit fishers extract from their use of the FADs. From August to December 2012, we placed GPS devices on a sample of fishing trips to track movement and measure variation in fishers’ fishing efforts at a set of seven FADs off the Atlantic east coast of central Dominica. The method produces high-resolution data to determine how much time different fishers use different FADs.

An Ecological Niche model was developed for skipjack tuna (Katsuwonus pelamis, SKJ) in the Eastern Central Atlantic Ocean (AO) and Western Indian Ocean (IO) using an extensive set of presence data collected by the European purse seine fleet (1998–2014). Chlorophyll-a fronts were used as proxy for food availability while mixed layer depth, sea surface temperature, dissolved oxygen, salinity, current intensity, and height anomaly variables were selected to describe SKJ's abiotic environmental preferences. The resultant ecological niche included both mesoscale eddy-type productive features that displayed latitudinal range in the IO to large scale upwelling systems that shrink and swell seasonally in the AO. Overall, 83% of all free swimming school sets (FSC) and 75% of drifting fish aggregating device sets (dFAD) that contained SKJ occurred within 25 km of favorable feeding habitat. In the AO, 34% of dFAD sets were made more than 100 km away from this habitat, mostly in the surface chlorophyll-a poor environment of the Guinea Current. These distant sets represent 10% of dFAD sets in the IO and 8% of all FSC sets. Our results suggest that the Mozambique Channel in the IO, with its simultaneously favorable feeding and spawning conditions, may seasonally offer a better SKJ nursery habitat than the Guinea Current which shows a substantially poorer feeding capacity. With the exception of this latter area, our results also suggest that fishing accessibility will be higher in months where the size of the favorable feeding habitats are reduced, likely because this reduction drives a geographical contraction in SKJ populations. The observed relationship between the annual size of favorable feeding habitat and both annual catch rates and total catches in the IO is consistent with the near-full exploitation of this stock that has occurred since the 2000s. Moreover, it suggests that annual habitat size could be used as an indicator of growth capacity for this highly productive stock. Habitat monitoring, as part of a dynamic fisheries management approach, should contribute to the sustainable exploitation of SKJ by providing information on the climate-dependent aspects of stock variability and the effects of dFAD deployment in food-rich habitats.

Aims: To examine the status of Fish Aggregating Device (Katha) fishery in the river Titas in Bangladesh and development of an alternative Katha fishery management strategy. Study Design: All Fish Aggregating Devices (Kathas) were recorded through a census survey. Fish catch monitoring facilitated through a regular catch survey of Katha/gear/team in operation. Place and Duration of Study: The study employed data collected from the river Titas in Brahmanbaria district of Bangladesh from 1997 to 2002. Methodology: A census of all constructed Fish Aggregating Devices (Kathas) in the study sites was undertaken. Catch data, including information on species composition and abundance, were collected from Katha fishers during the harvest season. Simultaneously a robust catch assessment was observed for four days per month. Randomly selected samples of catch by species by gear are recorded for each gear type. Results: Katha fisheries in this river accounted for 28%, 20%, 34%, 34%, 37% and 25% of annual fish production in 1997, 1998, 1999, 2000, 2001 and 2002 respectively. Significant (pKatha and survey catch were found in this river. However, species distributions in Katha catch are not significantly different in the years 1997 to 2002 at the 5% level. Conclusion: Katha fishery in the river system generally has a detrimental impact on fisheries resources as well as reducing fishing opportunities for poor and marginal fishers.

International audience; 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.