Fish Aggregating Devices Fishery Research Articles

Data Provision for Science-Based FAD Fishery Management: Spanish FAD Management Plan as a Case Study

The use of fish aggregating devices (FADs) in tropical tuna fisheries has increased significantly during recent decades. Concurrently, concern about juvenile tuna mortality, bycatch, and marine debris associated with FAD fisheries increased, and this led to the implementation of FAD management measures and more sustainable designs (e.g., non-entangling or biodegradable FADs, limits on active FADs, etc.). This document reviews data collection and reporting requirements of tuna-Regional Fisheries Management Organizations (t-RFMOs) on drifting FADs and summarizes the work carried out since 2010 under the Spanish FAD management plan to create an adequate standard data collection aimed at improving science-based decision making. The aim of this study is to assist in the strengthening of data collection systems through: (1) a review of the existing data requirements, (2) a review of the status of FAD data collection worldwide and identification of data gaps, and (3) recommendations aimed at improving FAD management through the strengthening of FAD data requirements. Due to the complexities of data collection, we summarize the difficulties faced when processing the data and propose concrete and practical solutions to improve both the data collection system and information quality.

Palm fiber as potential material for FADs: durability enhancement and increasing fish catching for small scale fisheries

Fish aggregating devices (FADs) have brought impact on the fish catching productivity and preciseness of fishing ground. Traditional fisherman is using coconut frond and areca frond for shallow water FADs and it have been increasing cost maintenance of FADs, due to durability of natural attractor like coconut frond and areca frond tend to lower. Therefore, the research aims to determine the influence of different natural attractors of the FADs (i.e., areca frond, coconut frond and palm fiber) to impact the fish catching around the shallow water FADs. Pyramid model was used for attractors of FADs. Data were collected by experimental method, i.e., experimental fishing every two weeks until the fronds (attractors) totally rotted using hand lines (January-May 2019). The location of research is Nagan Raya Waters, Aceh Province (Hindia Ocean). One-way analysis of variance (ANOVA) was conducted to assess differences in the treatment value, namely natural attractors in the FADs for the fish catching number (significant level at 95%). The results showed that the different of natural attractors of the FADs were affected to fish catching around the FADs. Meanwhile, palm fiber attractor is better than to aggregate of fish around FADs, but these has not given significantly different for total catch of fish (p>0.05). Therefore, to maximize fish catch around shallow water FADs and to minimize of maintenance cost for FAD are suggested to using palm fiber attractors. This finding is very important to help traditional FADs fishery in maximizing production of fish and to increasing profit of small scale fisheries.

Socio-economic prospects and problems in under-exploited offshore marine fisheries: The case of Fish Aggregating Devices (FADs) in Kenya coastal fisheries

Existing fishing methods and traditional vessels used by artisanal fishers in Kenya coast confine them to overfished sheltered reef areas and are not efficient enough to harvest a scattered resource. Fish Aggregation Devices (FADs) have been proposed as a new technological frontier with better prospects for capture of high valued fish species like tuna, thus improving income to coastal fishers. However, the reception of this technology by artisanal fishers has not been assessed in spite of implementation of various experimental FADs projects in the region. This study provides socio-economics insights with which to view the current status of Kenya’s FADs fishery. Survey data was collected through a combination of questionnaires and participant observations. Results reveal that fishing activities are still undertaken within the shallow protected waters of the barrier reef by artisans who operate small non-mechanized crafts. Fishing time is still relatively high (7hrs/day) even though the most prevalent gear is the traditional basket trap (43%). The modal daily income for fishers averaged at KES 400 (∼US$3.9). Only 13% of the fishers were adequately aware of FADs, among whom, FAD fishers who had been engaged in previous experimental projects rated FADs as highly effective (72%). The shortcomings of FADs included: increase in theft and vandalism of equipment (50%), attraction of illegal fishers (25%), and fisher–fisher conflicts due to little sensitization. Overall, fishers viewed FADs projects as unsustainable, since the required expertise is scarce while the equipment is expensive. We recommend the need for development of a user-right friendly approach to communal fishing offered by the FADs framework, and the fabrication of these FADs from locally available materials in order to enable fishers and local industry to run and advance the technology.

Evaluating potential biodegradable twines for use in the tropical tuna FAD fishery

Despite several ecological and environmental concerns (e.g. increasing marine debris, stranding events), thousands of man-made drifting Fish Aggregating Devices (FADs) are deployed annually by the industrial tuna purse seiners worldwide. Yet, the use of biodegradable materials to construct the underwater part of the FAD has not been explored in detail to date. In this study, scientists, industry, and twine manufacturers collaborate to test and evaluate different potential biodegradable materials and twine designs that can be used in the FAD fishery. Results showed that different materials and designs degrade differently over the study period and that they play an important role in the lifetime of the twines. Results showed that the estimated time to failure (i.e. when breaking strength reaches 0 kgf) ranged between 193 and 557 days for the tested twines. Because twine performance may vary in real fishing tropical conditions, we recommend further experiments in which a new specific twine should be developed and tested: a twisted and bulked cotton, sisal and linen twine. The use of new biodegradable materials and designs are discussed under a global perspective, as well as its implications for conservation, management and relevant future lines of investigation.

The use of echo-sounder buoys in Mediterranean Sea: A new technological approach for a sustainable FADs fishery

In the Mediterranean Sea, dolphinfish fishery has employed a great number of anchored Fish Aggregating Devices (FADs) arranged in lines, that represents a threat to navigation and to the marine environment and is economically disadvantageous to fishers. In this research, echo-sounder buoys were tested for the first time in the Mediterranean, and it was evaluated if this technological method can be useful to studies aimed to reduce the impact of FADs from the perspective of sustainable fishery.The study was carried out in November and December 2015 in a Tyrrhenian area where echo-sounder buoys were tied to anchored and drifting FADs and aggregated biomass estimates were recorded daily. Comparisons were made to evaluate whether there are: a relation between the number of anchored FADs and associated biomass; and differences, in terms of aggregated biomass, between anchored and drifting FADs.No clear correlation was found between the number of anchored FADs and biomass, while the drifting FADs showed a greater power of attraction than the anchored FADs. Anyway, the echo-sounder buoys may be suitable for future studies. It was highlighted that their simple use in the Mediterranean FADs fishery could facilitate a reduction of the high number of anchored FADs.

Fine-scale 3-dimensional movement behaviour of silky sharks Carcharhinus falciformis associated with fish aggregating devices (FADs)

The silky shark Carcharhinus falciformis is the primary elasmobranch bycatch in the global tuna purse seine fishery using fish aggregating devices (FADs). Information on the associa- tive behaviour of this species with floating objects remains limited. Here the use of various elec- tronic tags provided important new insight into this behaviour. Thirty-eight juvenile silky sharks (69 to 116 cm total length; TL) were tagged with acoustic tags at 9 drifting FADs equipped with satellite-linked acoustic receivers in the western Indian Ocean (total monitoring = 154 d). Pres- ence/absence and swimming depth data were transmitted from the receivers. A subset of 17 indi- viduals was also fitted with pop-up satellite archival tags (PSATs; n = 13), or internal archival tags (n = 4). Behavioural data were successfully collected from 20 of the tagged sharks, covering a total of 300 d. Fine-scale movements of one individual were observed by active tracking, lasting 2 h 46 min. Sharks remained associated with the FAD where they were tagged for extended periods (2.84 to 30.60 d, mean = 15.69 d). Strong diel changes were observed in both FAD association and swimming depth. Typically, individuals moved away from FADs after sunset and returned later that night, then remained closely associated until the following evening. Vertical behaviour also changed around sunset, with sharks using fairly constant depths, >25 m, during the day and switching to rapid vertical movements during the night, with descents >250 m recorded. The actively tracked individual returned to a FAD from >1.2 km away. Long residence times and close association highlight the vulnerability of silky sharks to incidental capture in FAD fisheries.

Age, Growth and Reproduction of Coryphaena hippurus (Linnaeus, 1758) in Maltese Waters, Central Mediterranean

Age, growth and reproduction of the dolphinfish Coryphaena hippurus Linnaeus, 1758 collected from the Central Mediterranean in the period 2004-2010 by the traditional Maltese fish aggregating devices (FAD) and surface longline fisheries were studied. The a and b parameters of the length-weight relationship for fish 11-142 cm fork length (FL) (n = 4042) were determined as a = 0.018 and 0.022 with b = 2.85 and 2.79, for males and females respectively. The counting of annual increments from dorsal spines of >65 cm FL dolphinfish at X25 magnification (n = 47) permitting an age reading resolution in years , and the counting of daily increments from sagittal otoliths of <65 cm FL dolphinfish at X400 magnification (n = 583) permitting an age reading resolution in days, were estimated; the von Bertalanffy growth model applied to these fish gave the following parameters: L∞ = 107.8 cm FL and 120.2 cm FL, and K = 1.9 yr-1 and 1.56 yr-1, for males and females respectively. The maximum age observed was 2 years. Size at 50% maturity for fish 10-131 cm FL (n = 1376) was 58.9 cm FL and 62.5 cm FL for males and females, respectively. The sex ratio for the fish sampled from the FAD fishery (10.5-131 cm FL) was 1:1.54 (M:F) and for dolphinfish sampled from the surface longline fishery (91-130 cm FL) was 1:0.76 (M:F). Back-calculated hatch dates from age-0 dolphinfish (n = 518) suggested that spawning occurs from June to September with the highest levels in June. This study is the first to use dorsal spines to determine the age of adult dolphinfish.

The FAD fishery in the Gulf of Thailand: time for management measures

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.

Fish aggregating devices (FADs): good or bad fishing tools? A question of scale and knowledge

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.

Assessing the fish assemblage associated with FADs (Fish Aggregating Devices) in the southern Tyrrhenian Sea using two different professional fishing gears

Fish Aggregating Devices (FADs) are used worldwide by fishermen to improve fishery yields, based on the finding that juveniles and adults of both pelagic and demersal fish species are attracted to floating objects. FADs fisheries are usually exploited using purse seine nets. In Sicilian seas, two different purse seines are used: (a) classic purse seine and (b) a transformed beach seine known as raustina. In this study we compared these two fishing gears in order to determine the best one for assessing fish diversity and to evaluate their impact on the species caught. We sampled the fishes associated with FADs from July to November 2003. Each haul was monitored by a SCUBA diver who observed the species escaping from the different types of net. Results showed that both gears catch the same fish species but significant differences in abundance were detected between gears. In particular, the purse seine caught a higher number of Thunnus thynnus than the beach seine (respectively: 8.2±1.1 vs 0.9±0.2), which in turn proved more efficient in catching C. crysos (31.4±3.7 vs 8.9±1.5 caught by purse seine). SCUBA observations revealed that T. thynnus escapes capture more easily from the beach seine than from the purse seine, due to their behaviour of swimming at a depth beneath that reached by the beach seine. On the other hand, the smallest specimens of C. crysos pass more easily through purse seine mesh, which is larger than beach seine mesh. Both gears are equally useful for assessing biodiversity associated with FADs, although they give different results for fish abundance. As the catches of FADs fishery target species (i.e. Coryphaena hippurus) were similar for the two gears, the modified beach seine could be proposed as a management tool to reduce the catches of young T. thynnus in accordance with European legislation.

The biology and ecology of juvenile pilotfish (Naucrates ductor) associated with Fish Aggregating Devices (FADs) in eastern Mediterranean waters

The pilotfish (Naucrates ductor) is an epipelagic oceanic species, whose 0-group specimens tend to aggregate below flotsam, constituting a principal by-catch of the western Mediterranean FAD fishery. During a one-year survey sampling, monthly experimental hauls using surrounding nets were conducted at sites in south Peloponnesian waters, where FADs were moored; during the summer-early autumn months bongo tows were also carried out. 0-group pilotfish appeared beneath FADs from mid-summer till early winter and the total length of the collected specimens ranged between 120 and 330 mm. Pilotfish larvae, measuring 2.0- 3.9 mm, were found at FAD sites in mid-summer and in early autumn. The age of juvenile specimens, determined by counting daily increments on their sagittae, ranged between 50-141 increments (days) for males, and 51-131 increments (days) for females. The predicted asymptotic length was found to be 412.3mm TL for males and 435.2 mm TL for females. The onset of sexual maturity appeared to occur when specimens were a few months old. Stomach content analysis suggested that the diet of 0-group pilotfish associated to FADs in Greek waters depended mainly on decapod larvae, hyperiid amphipods, and alciopid polychaetes.

Periodic behavior and residence time of yellowfin and bigeye tuna associated with fish aggregating devices around Okinawa Islands, as identified with automated listening stations

In order to better understand the associative behavior of yellowfin tuna (Thunnus albacares) and bigeye tuna (T. obesus) with anchored fish aggregating devices (FADs), we conducted long-term monitoring of these tuna tagged with ultrasonic transmitters, using automated receivers deployed on seven FADs around the Okinawa Islands. Current and surface water temperature were also monitored by data loggers attached to the stations as a way to examine the influence of these factors on the associative behavior of tuna with FADs. We monitored a total of 52 yellowfin and 11 bigeye tuna at monitoring FADs for a period of 2.5 years. We found that the majority of tuna remained continuously at the monitoring stations for a certain period (max.=55 days) without day-scale (>24 h) absences, until they left the stations completely. The residence time at a single FAD was estimated to be about 7 days, as the half-life for both yellowfin and bigeye tuna. No inter-specific differences were seen, though there was a significant difference in residence time between two size classes: the residence time of the larger size class was shorter than that of the smaller size class. We also found there was a periodicity of approximately 24 h and regularity of associative behavior, estimated based on the fluctuation pattern of the detection rate and of short-term (<24 h) absences. In particular, absences of several hours occurring once a day with high temporal precision were considered to be excursions within several nautical miles from the FADs. These results indicate that tuna express periodic behavior in relation to the FADs and can locate the FADs precisely enough to return to them after a certain time. No relationship was seen between associative behavior and abiotic oceanographic conditions. Therefore, the biological environment (prey availability, the presence of predators, etc.) and the internal state of the individual (hunger, etc.) may be more important than abiotic environmental cues for inducing changes in associative behavior and/or the departure from FADs. In addition, the strong association of tuna with a single FAD and the relatively prolonged residence time observed in the present study may relate to the vigorous activity of FAD fisheries in Okinawa and their utilization of a large amount of bait.

Food consumption of tuna in the Equatorial Atlantic ocean: FAD-associated versus unassociated schools

Since 1991, fishing operations on tuna schools associated with drifting Fish Aggregating Devices (FADs) have become widespread in the purse seine fishery in the Gulf of Guinea. In the offshore South Sherbro area (0–5° N, 10–20° W), FAD-associated catches represent about 75 % of the total catch. This FAD fishery exploits concentrations of skipjack mixed with a smaller amount of bigeye and yellowfin tuna of similar size (46 cm), and some large yellowfin. Catches on unassociated tuna schools are mainly composed of large yellowfin in breeding phase and skipjack. Here we studied tuna diet in relation with the aggregation mode (FAD-associated or unassociated tuna schools), species, and size. The stomach contents of around 800 fish were analysed. Numerous empty stomachs were found, especially in fish caught under FADs. Diets were similar for all small-size tuna sharing the same aggregation type. Small tuna mainly feed on Vinciguerria nimbaria (Photichthyidae), a mesopelagic fish of the micronekton, whereas large tuna mainly feed on Scombridae, mixed with Cubiceps pauciradiatus (Nomeidae) when they were caught in unassociated schools. The feeding habits of tuna are discussed with emphasis on the behavior of V. nimbaria. Estimations of the daily ration of similarly sized tuna with the same aggregation mode were very close. The low estimated rations for small, FAD-associated tuna show that logs do not have a trophic function, but rather are a refuge. In contrast, FADs seem to influence the diet of large tuna because of the Scombridae prey that probably is associated to the FAD.

Exploitation of small tunas by a purse-seine fishery with fish aggregating devices and their feeding ecology in an eastern tropical Atlantic ecosystem

We investigated the effects of a purse-seine fishery with drifting fish aggregating devices (FADs) in the South Sherbo area of the Equatorial Atlantic, located between 0–5N and 10–20W. There had been no surface fishing activity in the area until 1975. Since 1991, fishing operations on schools of tuna associated with FADs has become widespread and this offshore area has developed into a major fishing zone. Exploitation rates are high between November and January. The fishery exploits multispecies concentrations of skipjack (71%), bigeye (15%), and yellowfin (14%) tunas of similar size (mode: 46-cm forklength). The use of FADs increased the vulnerability of small tunas and induced changes in fishing patterns. The mean individual weight of skipjack caught has decreased since 1991, due either to overfishing or to a growth change. Data from scientific observers were used to estimate discards and by-catches generated by FAD fishing during 1998. Discards of tunas (including frigate and little tunas) represented 7.6% of the total catch. Other by-catch (dominated by wahoo, billfish, triggerfish, sharks, barracudas, and dolphinfish) represented 2.3%, including 0.4% discarded at sea. Stomach content analysis showed that a mesopelagic species, Vinciguerria nimbaria (Photichthyidae), which during daylight concentrated in the upper layers in dense schools, was the main prey of all small tunas. The South Sherbro area appears to have exceptional environmental conditions. It is suggested that the FAD fishery may have wide-ranging effects on the migration of tunas in general and on the productivity of the skipjack population in particular.