Line Fishery Research Articles

An assessment of Post-Harvest Fish Losses (PHFLs) in the artisanal fishery of Lake Kariba, Zimbabwe

Post-harvest fish losses (PHFLs) occur in fisheries worldwide leading to global losses estimated at 10 - 12 million tons/year. Lack of information on PHFLs makes it difficult to formulate appropriate fisheries management policies and interventions. This study investigated PHFLs in the artisanal fishery on Lake Kariba, Zimbabwe. Qualitative and quantitative methods of data collection were used. Using descriptive statistics the questionnaire loss assessment method (QLAM) revealed that the rod and line fishery and the gill-net fishery had a total loss of 1.5% and 1.8% respectively. Primary field data showed zero per cent loss in the rod & line fishery while the gill-net fishery had a loss of 1.9%. The minimal PHFLs experienced were attributed to the good fish handling practices and the low fish catches (< 40 kg/day/per fisher). The daily fish catches could be processed adequately and fishers ensured very little was lost because they are operating on the economic margins of sustainability. The major types of losses experienced were physical losses, quality losses and drip loss. Physical losses were higher in the rod & line fishery while quality losses were prevalent in the gill-net fishery. Drip loss was only unique to fish traders who reported a drip loss of less than 4.5%. State seizures, predation by crocodiles (Crocodylus niloticus), theft and destruction of gill-nets by kapenta fishing rigs were also ancillary factors contributing to PHFLs. Other major determinants of losses reported in this study were higher temperatures, direct sunlight, late hauling, poor handling of fish, poor storages and negligence. Proximate analysis was carried out for fresh, iced, frozen and salt and dried fish samples and the following parameters were analysed:moisture content, ash content, fat content and protein content. There were significant differences (p< 0.05) among the various fish samples that were analysed. However, Tukey's post-hoc analysis revealed that only dried fish samples were significantly different from the rest of the fish samples. The traditional fish preservation methods employed in this fishery did not have negative impact on the nutritional composition of fish. The use of ice, refrigerators, salting and sun drying are recommended as preservation methods in the artisanal fishery. The sun drying method proved to offer high nutritional values and longer shelf life for fish.

Monitoring the reproductive status of resident and migrant Atlantic bluefin tuna in the Strait of Gibraltar

Two distinct contingents of Atlantic bluefin tuna (ABFT), migrants and residents, occur in the Strait of Gibraltar (SoG). Long-term residents are commercially exploited all year round using hook and line gears, whereas migrants are caught by traps in springtime as they pass through the SoG towards Mediterranean spawning grounds. While reproductive features of migrants have been widely studied, the life history of residents remains poorly investigated. The relative contribution of this subpopulation to ABFT eastern stock productivity is therefore unknown. Reproductive traits of resident ABFT were monitored throughout the year, and were compared with those of migrants crossing the SoG in spring. To assess maturation timing, gonads were classified into maturation stages based on histological features. Our results indicate biometric and reproductive differences between SoG residents and migrants. ABFT caught by hook and line gears were smaller on average than those collected from traps. The females sampled from the hook and line fishery in May and early June showed, on average, significantly lower GSI values than those caught by trap. In contrast, the GSI values of males sampled in May were not significantly different between gears. Histological analyses showed a more advanced reproductive condition in trap-caught migrants. Delayed maturation schedules of residents in comparison to migrants would result in less egg production and poorer larval survival rates. The present findings encourage further investigation of reproductive schedules in unstudied subpopulations for a better understanding of ABFT dynamics.

Fuel consumption of free-swimming school versus FAD strategies in tropical tuna purse seine fishing

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.

CHARACTERIZING OF SKIPJACK (Katsuwonus pelamis) SUPPLY CHAIN ON POLE AND LINE FISHERY IN INDONESIA FMA 714 AND ADJACENT: A CASE STUDY IN SIKKA REGENCY, WEST NUSA TENGGARA-INDONESIA

In order to obtain detailed characteristic of skipjack (SKJ) supply chain on pole and line (PL) fishery operates in Indonesia Fisheries Management Area (I-FMA) 714 and its adjacent areas, Center for Fisheries Research (CFR)-MMAF with WCPFC carried out a research in Sikka Regency. Data and infomation obtained through port sampling program, observer program and stakeholders workshop. Result shows that primary actors and processes of supply chain of skipjack on PL fishery based in Sikka consisted of PL fishers (skipper and crews), collector and traders, processors and market. Total active PL boats were 67 which supported by ± 40 lift-net (bagan) to provide 300-400 tonnesnes live bait, 11 small-medium scale and 5 large scale collectors and traders, 5 small and 4 large processors and local, domestik, export market. About 3556.9 tonnes SKJ caught by PL based in Sikka in 2017, about 56% were processed as katsuwobushi (smoke fish) for being exported to Japan, 35 % were frozen processed for being exported and marketed to Europe-US and domestic market in Makassar, Bali, and Surabaya. About 9% of the total catch of PL fishery based in Sikka were locally marketed as cold-fresh SKJ.

Catching performance and catching efficiency of siliconized baits in hand line fishery

The present study investigated the catching performance and catching efficiency of natural mud shrimp (alive) (Upogebia pusilla), siliconized mud shrimp and siliconized pellet in handline fishing. The trials were performed in Kıyıkışlacık Village of Muğla province. The main body of the handline is Ø 0.50 mm, leader and snood are Ø 0.27-0.30 mm, the snood length and distance are 10 cm and 20 cm, respectively. Each handline has 3 hooks and the hook type is 4 no straight. Catches from natural mud shrimp, siliconized shrimp and siliconized pellet bait retained separately, sorted by species and weighed as. 0.01 g sensitivity and measured as the total length. Totally 590 individuals from 30 different species in total were caught including; 28 bony fish (93.33%), and 2 cephalopods (0.66%). While natural mud shrimp captured the 50.7% of fish, 44.7% and 4.6% were caught with siliconized mud shrimp and siliconized pellet, respectively. CPUE values of natural mud shrimp, siliconized shrimp and silicon pellet were calculated as 1.57 n/h, 1.38 n/h and 0.14 n/h, respectively. In addition, YPUE values were determined as 121.84 g/h, 137.73 g/h and 7.62 g/h for natural mud shrimp, siliconized shrimp and silicon pellet, respectively. Despite the fact that the number of individuals that a live mud shrimp catch in a unit of time is high, it was found out that the weight is more in a unit of time when silicone mud shrimp is used. It was concluded that using of siliconized mud shrimp has a high capacity of catching performance and catching efficiency and can be used as bait when natural mud shrimp cannot be utilized as alive or unable to be supplied, due to the weather conditions and time restrictions.

Site fidelity, spatial use, and behavior of dwarf sperm whales in Hawaiian waters: using small‐boat surveys, photo‐identification, and unmanned aerial systems to study a difficult‐to‐study species

AbstractDwarf sperm whales (Kogia sima) have been studied rarely at sea. We used photo‐identification, boat‐ and drone‐based behavioral observations, and citizen science photo contributions to examine site fidelity, spatial use, and behavior in Hawaiʻi. Sighting rates were highest in island slope (500–1,000 m) waters. Over 40% of photo‐identified individuals were linked by association in the same social network. More than half of the very distinctive individuals were seen more than once, and 28.5% were seen in multiple years, with one individual seen 14 times over a 15‐year span. Resighted individuals and those in the main cluster of the social network were found in significantly shallower water than individuals that were not resighted or that were in isolated clusters. Distances between resighting locations suggest small home ranges. This suggests an insular slope‐dwelling population that overlaps with an offshore population. Evidence of unsuccessful predatory attempts by large sharks was recorded on four individuals, and linear wounds consistent with interactions with line fisheries were documented on three individuals. Surface and subsurface behavior recorded by drone revealed vigilance behavior likely to minimize predation risk. Lessons learned from this study can be applied elsewhere to increase knowledge of this poorly known and difficult‐to‐study species.

Carbon footprint of tuna and tuna like production landed based at Bitung fish port

It is well known that greenhouse gas effects are one of the main factors driving global warming. Substances that play a role in this phenomenon include Carbon dioxide (CO2), Methane (CH4) and Nitrous oxide (N2O) which is commonly called as Carbon Substances. The higher the levels of these substances in the air, the greater and faster impact of the greenhouse phenomenon can cause. The current status of global warming has encouraged us to make efforts to reduce and mitigate climate change. Calculation of the addition of carbon substances (Carbon Footprint Inventory - CFI) is the first step in an effort to deal with climate change. It is therefore, as one form of participation in the mitigation of global warming, the calculation of carbon production (carbon footprint) in Tunas (Tuna, Mackerel Tuna and Skipjack) fisheries has been done. The research was subject to Tunas production captured using Pole and Line and landed at Bitung fisheries port. This research utilized primary data collected by field survey, questionnaire, expert adjustment, and secondary data from various data sources both online and offline. The number of respondents were 16 fleets of Pole and Line based in Bitung fisheries port, including its captains, engine master and fishing master in each fleet. Several companies such as ice factories, processing and fuel dealers were also subjected as respondents. Flow charts and Life Cycle Analysis (LCA) are used to map the needs and availability of data which are then applied to CFI based on ISO / TS 14067. CFI ISO/TS 14067 internationally has been published specifically to calculate the CFI of products. The result shows CFI of Tunas product in Bitung was 1.41 ± 0.80 kgCO2/kg of Tuna. This number is considered low compared to the CFI tuna fisheries on an international scale reported by the environmental working group - Americans for Prosperity (AFP) which is about 6.1 kg CO2/kg of fish. Unfortunately the report from AFP was stated in the general without recognizing the fishing gear whereas in this research it had only calculated the CFI on Pole and Line fisheries.

Spawning aggregation sites of the cubera snapper, Lutjanus cyanopterus, on the continental shelf of Bahia state, Northeastern Brazil

The cubera snapper (caranha), Lutjanus cyanopterus, is an important resource for reef fisheries in Northeastern Brazil, currently classified as Vulnerable (VU) on the Red List of Threatened Species. This species forms large transient reproductive aggregations, concentrating their reproductive efforts in a short period of the year and in specific spawning sites, which have already been well documented in the Caribbean. These aggregations are predictable in time and space, making them considerably vulnerable to overfishing and other sources of anthropic impacts. These tend to reduce the population’s renewal capacity and genetic diversity, thus contributing to the decline of fish stocks and to the process of local extinctions. Between 2009 and 2010 we identified two L. cyanopterus aggregation sites, commonly known as “Caranheiros”, in two sub-areas located at the continental shelf-break zone of Bahia state, Northeastern Brazil, in the East Brazil Shelf Large Marine Ecosystem (LME16), between latitudes 12 °S and 15 °S. The present study aims to (1) describe patterns of spatial and temporal distribution, and the biological characteristics of L. cyanopterus’ catches from line fisheries targeting the specific aggregations in the two Caranheiros sites; and (2) validate the reproductive character of these aggregations through macroscopic evaluation of sexual maturity phases of the fishes caught. We analyzed fisheries and biological sampling data from the catches of artisanal fleets monitored in the two sub-areas between 2005 and 2014. The identified aggregations occur annually from December to May, with capture peaks concentrated in waning to waxing moon phases, in January, February and March. The predominance of mature, pre-spawning and spent (recent spawning) individuals, males and females, in these aggregations revealed the reproductive activity in both sites. Identifying and validating these spawning sites may contribute to the development of recovery and conservation plans for this threatened species. The continuous monitoring of fisheries on aggregations is a priority, aiming to trigger management responses and adaptative fisheries management. Considering these sites are highly vulnerable and have high local socioeconomical importance, especially to traditional fishers, the exact location of the analyzed “Caranheiros” is not revealed in this publication. However, it has been made available to the government agencies responsible for fisheries control and surveillance, as well as for implementing management and conservation measures for the sustainable use of fisheries resources.

Financial feasibility of hand line fisheries and determination of tuna production in Ambon Island

The potential availability of fish resources can be utilized in various economic activities to improve the welfare of coastal communities. The utilization of tuna by using hand line is still carried out by small and medium scale fisheries with some limitations, such as technical production, costs and management skills. The purpose of this study was to describe the technical profile of tuna fishery production in Ambon Island, specifically in Negeri Tial and Negeri Laha; analyze the absolute profit level of tuna fishermen; analyze hand line fisheries business feasibility; and determine the efficient fishing input. Negeri Tial and Laha are the centers of handline fisheries in Ambon Island. This study was conducted by survey. Primary data collection through empirically constructed questionnaires and secondary data obtained from several related agencies. Samples were taken purposively, so that the number of samples in each Negeri was 20 units. A qualitative method approach is used to describe the technicalities of tuna fisheries production, while for other purposes a quantitative approach is used. The results showed that in increasing production, tuna fishermen in Tial and Laha used relatively the same type of hand line and fishing vessel size, but the use of artificial bait in Laha was more varied. Both research objects gain advantages and are feasible to be developed. Fishing input that is efficient in increasing production is the experience of fishermen and the frequency of fishing. Based on the research results, hand line tuna fisheries in Negeri Tial and Laha can be developed to improve the welfare of business actors.

Effect of bait availability on pole and line fisheries and the impact on the amount of fish consumption

Pole and line fisheries are highly dependent on bait availability. The problem of bait lies in-stock availability and improper handling methods cause the bait to become stressed and die. This research aimed to analyse the effect of bait on the pole and line fishing process. This research was a survey through field observations. This research used descriptive analysis. Data were collected including on bait, the fishing process, and catch. The results showed that the pole and line process was one-day fishing. The bait volume used was 25 buckets. The pole and line catching process is quite involved and includes the process of transferring the live bait from the hold into the stocking tank using a large hand net with a 32 cm diameter, the chumming process or the process of spreading live bait using a small scoop net with a diameter of 13.5 cm, and the actual fishing process. The total catch was 500 individuals/trip or 2.5 tons, including Katsuwonus pelamis, Euthynnus affinis, Thunnus albacares and Coryphaena hippurus. Fishing was carried out as a one-day fishing process because it was based on the availability of bait. Fish resource utilization is managed by fishermen optimally because it affects fish consumption.

Peningkatan Hard Skill Sistem Informasi Digital Perikanan Tangkap di Era Digital 4.0

fishermen must be adaptive to technological advancement. Community service in the form of increasing the hard skill of the digital information system for fishing fishing in the digital era aims to make it easier for fishermen to carry out their livelihood activities. Activities are carried out online for theory and offline for practice. The target partners were trained as many as 30 people from the hand line fishery community of the Maladum Mes district. The results of monitoring the target partners can practice the material presented.

Estimating discard mortality using meta-analysis and fishery-dependent sampling

Estimates of discard mortality are difficult to obtain. Meta-analysis or life-history-based approaches to estimate discard mortality could provide informed estimates when direct empirical estimates are not available. We used data from published literature across a variety of fish species to determine if hooking condition (good vs. poor) and species-specific values for the Brody growth coefficient (K: a measure of fish physiology) were meaningful factors influencing discard mortality in hook and line fisheries. We then examined whether a two-step approach, combining condition- and physiology-specific estimates of discard mortality with data on proportion-by-hooking-condition hooking information for a fishery, could result in an estimate of discard mortality for dolphinfish Coryphaena hippurus comparable to an empirical estimate. A model with hooking condition, K and their interaction best fitted the published discard mortality data. K was an important negative covariate of discard mortality for good hooking condition, with higher K species experiencing greater rates of survival. In contrast, species in poor condition had similarly low rates of survival across a range of K values. Results suggests that hooking condition is the dominant source of mortality when fish are hooked in vital areas but that physiology should also be taken into account when estimating discard mortality for good condition fish. For the recreational dolphinfish fishery in the southeastern US, we estimated a median proportional discard mortality rate of 0.12 (95 % credible set: 0.07, 0.17) when combining the meta-analysis and field-collected proportion-by-condition data. This estimate was lower than the empirical estimate of dolphinfish discard mortality but the credible sets overlapped (median: 0.25; 95 % credible set: 0.05, 0.39). Estimates of discard mortality from our meta-analytic approach may be applicable to fisheries where empirical estimates of discard mortality are not available and hooking injuries are the dominant source of mortality.

Vulnerability level of target and by-catch species on tuna hand line (HL-TR) fishery in Indonesian Fisheries Management Area I-FMA 573 based at Sadeng Fishing Port

Tuna hand line-trolling line (HL-TR) fisheries have an essential role in Indonesia’s tuna fisheries, including Indonesia Fisheries Management Areas (I-FMAs) 572 and 573. The catch of tuna line in I-FMA 572 and 573 reached ~30.4% of the total catch 189,022 tonnes in 2019. Limited data and scientific advice for developing adequate management remain a challenge for tuna HL-TR fisheries in I-FMA 573 waters. Center for Fisheries Research (CFR) has conducted an assessment using the PSA method to obtain information of vulnerability level both of target and bycatch species on tuna HL-TR in 2020. Data used in the analysis were grouped into operational fishing, productivity, and susceptibility data. The operational fishing data were obtained from Sadeng Fishing Port in2019. The productivity and susceptibility data were obtained from literature review and expert consultation through a Focus Group Discussion (FGD) and expert consultative workshop. The result showed that both target and by-catch species included in the analysis have low to moderate vulnerability level scores. The results of this research are used to help managers at a national level to determine necessary management measures with high precautionary. While for by-catch species, in particular white tip sharks, its management measures must comply with agreed IOTC regulations.

Fish stock demographics of skipjack tuna (Katsuwonus pelamis) from Kavaratti in Lakshadweep, Southern Arabian Sea

Marine fish stocks are depleting at an alarming rate. Skipjack tuna, Katsuwonus pelamis has been exploited in Lakshadweep Island area in the Indian Ocean mainly by pole and line fishery which constituted one-third of its production in the country. Age, growth, demographics and stock assessment of this species were investigated from the Lakshadweep waters. The von Bertalanffy growth factors were estimated as asymptotic length 72.5 cm, growth constant 0.480 and the theoretical age at zero-length as –0.1097. This study showed that skipjack grows from 30 to 68.26 cm from first to sixth year. The natural mortality, fishing mortality and total mortality were 0.82, 1.51 and 2.33 respectively. The exploitation ratio was 0.65, while the exploitation which maximises relative yield per recruit (Emax) was 1.0. Recruitment pattern showed that young recruits entered the fishing grounds in most months, with peaks during June–July. Length based Virtual Population Analysis indicated that the major loss in its stock up to 22 cm was due to natural causes. At the same time, higher fishing mortality was registered in 40–60 cm length group. The present study provides knowledge on the demographics of K. pelamis, pertinent for formulating an effective fisheries management in the region.

Seafood certification schemes in Japan: Examples of challenges and opportunities from three Marine Stewardship Council (MSC) applicants

While there has been a global proliferation of marine certification schemes aiming to incentivize sustainable fishing in the last decade, the uptake has been comparatively slow in Japan. Suggested reasons include difficulties assessing Japanese fisheries co-management institutions, and reduced profitability from complex seafood distribution networks and mismatched consumer preferences. However, a few Japanese fisheries have been awarded the international Marine Stewardship Council (MSC) certification. This paper investigates the motivations and experiences of three such MSC applicants: the Kyoto Danish Seine Fisheries Federation offshore fishery, Ishihara Marine Products skipjack and albacore pole and line fishery, and Maruto Suisan rope grown Pacific oyster fishery. Semi-structured interviews were conducted with key informants from each case study and coded into motivations, problems and impacts. It was found that although there were economic motivations to apply for the certification, this mainly involved increasing domestic distribution channels rather than gaining or retaining access to premium-paying foreign markets. The co-management system that governs the Kyoto fisheries hampered the re-certification process of the fishery due to the difficulty of influencing the higher levels of management within the system. It also became clear that the type of applicant was important to consider: the two more recent MSC clients – both seafood processors – are better placed in the value chain to utilize the certification and its logo, and therefore more likely to financially sustain the certification. The study provides an important insight into the applicant experience of certification schemes in countries with lower consumer demand for them, such as Japan.

Dependency of Queensland and the Great Barrier Reef\u2019s tropical fisheries on reef-associated fish

Coral reefs have been subject to mass coral bleaching, potentially causing rapid and widespread degradation of ecosystem services that depend on live coral cover, such as fisheries catch. Fisheries species in tropical waters associate with a wide range of habitats, so assessing the dependency of fisheries on coral reefs is important for guiding fishery responses to coral reef degradation. This study aimed to determine how fisheries catches associate with coral reefs in Queensland, Australia. Queensland’s largest fisheries did not target fish associated with reefs, but specific sectors, particularly aquarium fisheries and commercial fisheries in the mid to northern region had a high dependence on species that use coral reefs. Regions that had a greater relative area of coral reefs had higher catches of species that depend on live coral, suggesting that coral area could be used to predict the sensitivity of a jurisdiction’s fisheries to bleaching. Dynamic analysis of stock trends found that coral trout and red throat emperor, the two largest species by catch for the reef line fishery, were at risk of overfishing if habitat loss caused declines in stock productivity. Management of fisheries that are highly dependent on reefs may need to adapt to declining productivity, but further research to support ongoing reforms in Queensland’s fisheries is needed to quantitatively link reef degradation to stock production parameters is needed.

The financial business characteristics of hand line fisheries in the SAP Area of Raja Ampat Islands and the surrounding sea

Aktivitas perikanan tangkap di Kawasan Suaka Alam Peraian (SAP) Kabupaten Raja Ampat sebagian besar adalah usaha perikanan skala kecil. Pengembangan usaha alat tangkap pancing ulur menjadi sangat penting untuk pemanfaatan secara berkelanjutan kegiatan perikanan tangkap skala kecil di kawasan konservasi. Tujuan dari penelitian ini adalah untuk menilai kelayakan usaha perikanan pancing ulur dari aspek finansial dan resiko pengembangannya di Kawasan SAP Kepulauan Raja Ampat dan laut sekitarnya. Jenis data yang dibutuhkan dalam penelitian ini adalah data primer dan sekunder. Analisis data yang digunakan dalam penelitian analisis parameter finansial, kriteria investasi dan analisis resiko usaha. Hasil penelitian menunjukkan bahwa usaha perikanan pancing ulur di Kawasan SAP Kabupaten Raja Ampat dan laut sekitarnya mendapatkan keuntungan dan layak untuk dikembangkan. Dilihat dari analisis kelayakan finansial usaha dengan nilai keuntungan sebesar Rp. 9.003.171,00, nilai R/C ratio sebesar 1,11 dan nilai payback periode (PP) sebesar 2,95 tahun. Dilihat dari kelayakan investasi menunjukkan bahwa nilai NPV&gt;0, net B/C&gt;1 dan IRR&gt; tingkat suku bunga yang berlaku 5,25%. Dilihat dari resikonya bahwa usaha pancing ulur masuk dalam kategori tidak beresiko untuk dikembangkan. Hasil ini dilihat dari nilai CV (0,2) ≤ 0,5 maka nilai L (8.428.400) ≥ 0, yang berarti perusahaan akan selalu untung atau impas dan tidak mengalami resiko kerugian.

Optimising harvest strategies over multiple objectives and stakeholder preferences

Natural resource management has long recognised that the multi-objective nature of management is important, but has struggled to operationalise this into quantitative, measurable objectives for functional use in management. Operationalising broader ecological and social objectives has been particularly problematic. In fisheries management, the focus has mainly been on target species sustainability and, in the past few decades, on profitability. However, multi-objective management is now essential as fisheries have become recognised as complex social-ecological-systems.Policy and legislation demand a move towards quantitative approaches for reconciling multiple objectives and operationalising these within harvest strategies. We present a quantitative, non-commensurable-unit approach, via a multi-indicator value function with explicit objective preference weights. We use a simulation to set Total Allowable Catches (TACs) for three main species groups in a reef line fishery in Australia's Great Barrier Reef. Our method enables stakeholders to consider a richer range of tradeoffs than is possible with bio-economic models. Moreover, it allows the formal evaluation of performance across alternative stakeholder group preferences, providing an impartial way to obtain an overall optimum TAC. The simulation requires extensive fishery data and requires the performance indicators associated with each objective to be quantitatively and defensibly defined. Thus, our approach provides a pathway forward that forces managers and stakeholders to confront the associated data requirements.

Seasonal changes of potential fishing ground formation for Skipjack Tuna in the Bone Gulf, Indonesia

Skipjack tuna (Katsuwonus pelamis) plays an important role by pole and line fishery in the Bone Gulf, Indonesia, since it has a high economic value and wide market acceptance. The purpose of this paper was to assess the seasonal changes of skipjack tuna potential fishing ground in the Bone Gulf. We used pole and line fishery and oceanographic data of sea surface temperature (SST) and chlorophyll-a derived from satellite to figure out the seasonal formation of the potential fishing areas. We developed the spatial model to determine the potential fishing ground based on different levels of oceanographic preferences. The results showed that potential fishing grounds were mostly formed in the first transition season (particularly in May) as well as the west season (especially in November), which have a good association with the specific SST and chlorophyll-a of near 30 Deg C and 0.2 mg m-3, respectively. Most of the potential skipjack fishing ground formation developed along with the specific oceanographic signatures. It was likely that the potential seasonal changes of fishing grounds corresponded with enhanced feeding opportunity distribution pattern for skipjack schools. This suggested that these potential areas play an important for conservation and skipjack fishing management within the study area.

STUDY ON SPECIES COMPOSITION OF JUVENILE TUNA CAUGHT BY PURSE SEINE FLEET LANDING IN TAMPERAN FISHING PORT, JAVA, INDONESIA

Juvenile yellowfin tuna (Thunnus albacares) and bigeye tuna (T. obesus) are very similar in morphological characteristics, hence it is difficult to distinguish between these two species, especially when they are landed in frozen or defect conditions. The presence of juvenile bigeye tuna in yellowfin catch was first noticed in the 1980s from pole and line fisheries in Maldives. We analyzed the monthly composition structure of juvenile tuna caught by purse seine fleet operating in the South Indian Ocean. Tamperan fishing port was chosen for benchmarking to other small-scale fisheries. The result is expected to be used as an index for increasing the accuracy of juvenile tuna proportion for national catch statistics. A total of 4760 juvenile tunas were examined during monitoring activities. The length ranged 19-65 cm FL with median 40 cm FL for juvenile yellowfin tuna and 44 cm for juvenile bigeye. The whole weight of juvenile tuna ranged from 5 to 7 kg. The length-weight conversion for both species are W = 0.0184*FL3.0086 (R2 = 0.95, n = 4144) for juvenile yellowfin tuna and W = 0.018*FL3.0047 (R2 = 0.93, n = 346) for juvenile bigeye tuna. It can be inferred from the study that in terms of catch proportion of juvenile tuna, it consists of ratio 10:1, whereas for every 10 kg of juvenile tuna contains approximately one kg of bigeye tuna. Besides, the length-weight equation for both species is interchangeable, which means either equation can be performed to convert length to weight for both juvenile yellowfin and bigeye tuna.