Yellowfin Tuna Research Articles

Pengaruh Perbandingan Tepung Tulang Ikan Tuna Sirip Kuning (Thunnus albacares) dan Terigu Terhadap Karakteristik Cookies Sebagai Makanan Fungsional Tinggi Kalsium


 
 
 The purpose of this study was to determine the effect of comparison yellowfin tuna fish bone and wheat flour on the characteristics of cookies and to determine the best comparison of yellowfin tuna fish bone to produce cookies with the best characteristics. The design used in this study was a completely randomized design (CRD) with treatment of the amount of flour and bone meal of yellowfin tuna consisting of 5 levels, that are 100%: 0%; 90%:10%; 80%:20%; 70%:30%; and 60%:40%. The treatment was repeated 3 times to obtain 15 experimental units. The data obtained were analyzed statistically using variance and if the treatment had a significant effect, it was continued with Duncan's Multiple Distance Test. The results showed that the ratio of flour and bone meal of yellowfin tuna had a significant effect on water content, ash content, protein content, fat content, carbohydrate content, calcium content, scoring test (color, texture, aroma, and taste) and hedonic test (color, aroma, and texture) cookies. Ratio of 60% flour with 40% yellowfin tuna fish bone produced cookies with the best characteristics with the criteria of water content 6.5%, ash content 13.17%, protein content 11.54%, fat content 46.85%, carbohydrates content 21.90%, calcium content 5.91%, characteristic of colour was brownish yellow and ordinary, aroma was fishy and ordinary, texture was crunchy and ordinary, taste was slightly typical of tuna and ordinary, and overall acceptance was ordinary.
 
 

Nursery origin of yellowfin tuna in the western Atlantic Ocean: significance of Caribbean Sea and trans-Atlantic migrants

Natural geochemical markers in the otolith of yellowfin tuna (Thunnus albacares) were used to establish nursery-specific signatures for investigating the origin of fish captured in the western Atlantic Ocean (WAO). Two classes of chemical markers (trace elements, stable isotopes) were used to first establish nursery-specific signatures of age-0 yellowfin tuna from four primary production zones in the Atlantic Ocean: Gulf of Mexico, Caribbean Sea, Cape Verde, and Gulf of Guinea. Next, mixture and individual assignment methods were applied to predict the origin of sub-adult and adult yellowfin tuna from two regions in the WAO (Gulf of Mexico, Mid Atlantic Bight) by relating otolith core signatures (corresponding to age-0 period) to baseline signatures of age-0 fish from each nursery. Significant numbers of migrants from Caribbean Sea and eastern Atlantic Ocean (EAO) production zones (Gulf of Guinea, Cape Verde) were detected in the WAO, suggesting that fisheries in this region were subsidized by outside spawning/nursery areas. Contributions from local production (Gulf of Mexico) were also evident in samples from both WAO fisheries, but highly variable from year to year. High levels of mixing by yellowfin tuna from the different production zones and pronounced interannual trends in nursery-specific contribution rates in the WAO emphasize the complex and dynamic nature of this species’ stock structure and population connectivity. Given that geographic shifts in distribution across national or political boundaries leads to governance and management challenges, this study highlights the need for temporally resolved estimates of nursery origin to refine assessment models and promote the sustainable harvest of this species.

Ecosystem Management Policy Implications Based on Tonga Main Tuna Species Catch Data 2002–2018

Despite the crucial role played by international and regional tuna fisheries in facilitating the successful implementation of the ecosystem approach to fisheries management, there exist disparities in viewpoints among these stakeholders, resulting in gaps between regional fisheries management and local communities. Nevertheless, the Tongan government, under the Ministry of Fisheries, is dedicated to the efficient management of its tuna resources, aiming to establish it as the preferred and optimal approach for ensuring the long-term sustainability of its tuna fisheries and the ecosystem services they provide to the community. Recognizing that an appropriate legal, policy and institutional framework is in place for sustainable management of tuna, the first part of this paper presents a review of current Tonga fisheries laws and policies for its tuna fisheries. This review reflects the implementation of an information-based management framework, namely the Tonga National Tuna Fishery Management and Development Plan. The tuna fisheries in Tonga mainly catch albacore (Thunnus alalunga), bigeye (Thunnus obesus), skipjack (Katsuwonus pelamis), and yellowfin (Thunnus albacares) tuna. These tuna species are caught within Tonga’s exclusive economic zones and play a crucial role in the country’s economy; hence, it is crucial to examine the spatio-temporal distributions of their catch in relation to their environmental conditions. In pursuit of this goal, the tasks of mapping (i) the spatio-temporal distribution of catch landed at ports and (ii) the spatio-temporal of environmental conditions were performed. The study utilizes longline catch per unit effort data spanning from 2002 to 2018 for albacore, bigeye, skipjack, and yellowfin tuna. It also incorporates data on environmental conditions, including sea surface temperature, sea surface chlorophyll, sea surface current, and sea surface salinity. Additionally, the El Nino Southern Oscillation Index is mapped in relation to catch data to examine the potential effects of climate change on the tuna catch. Results show that bigeye, skipjack, and yellowfin CPUE show a central–northernmost distribution and are primarily caught between latitudes 14° S–22° S, while albacore, shows a central–southern distribution. The highest CPUE for all species are in latitudes 15.5° S–22.5° S and longitudes 172.5° W–176.5° W. The data indicate that sea surface current velocities range from −0.03 to 0.04 ms−1, sea surface salinity ranges from 34.8 to 35.6 PSU, sea surface chlorophyll concentration varies from 0.03 to 0.1 mg m−3, and sea surface temperature fluctuates seasonally, ranging from 18 °C to 30 °C. Mapping also reveals that times of reduced catches in Tonga coincide with periods of moderate to strong El Nino events from 2002 to 2018.

The effect of ocean acidification on otolith morphology in larvae of a tropical, epipelagic fish species, yellowfin tuna (Thunnus albacares)

Increasing ocean acidification is a concern due to its potential effects on the growth, development, and survival of early life stages of tuna in oceanic habitats and on the spatial extent of their suitable nursery habitat. To investigate the potential effects of increasing CO2 on otolith calcification of 9-day old pre-flexion stage yellowfin tuna (Thunnus albacares), an experiment was conducted at the Inter-American Tropical Tuna Commission's Achotines Laboratory in Panama during 2011. Fertilized eggs and larvae were exposed to mean pCO2 levels that ranged from present day (355 μatm) to two levels predicted to occur in some areas of the Pacific in the near future (2013 and 3321 μatm), and to an extreme value equivalent to long-term projections for 300 years in the future (9624 μatm). The results indicated significantly larger otoliths (in area and perimeter) with significant, and increasing, fluctuating asymmetry at acidification levels similar to those projected for the near future and long-term. Otoliths increased significantly in size despite a significant decrease in somatic length with increasing pCO2. A consistent correlation between otolith and somatic growth of yellowfin tuna larvae among treatments was evident (i.e., larger otoliths were still associated with larger larvae within a treatment). The observed changes in otolith morphology with increasing ocean acidification have the potential to indirectly affect larval survival through dysfunction of the mechanosensory organs, but this remains to be verified in yellowfin tuna larvae.

Assessment of biogenic amines in commercial tuna fish: Influence of species, capture method, and processing on quality and safety

This study investigated the influence of species, capture method, chilling, and freezing on the quality and variations in biogenic amines of Thunnus tonggol and Thunnus albacares. Samples were collected from different sources, including fisheries ports, cold rooms, and canning factories. The results indicated that canned fish had significantly higher levels of biogenic amines, especially histamine, compared to raw fish from ports and cold rooms. However, all canned samples complied with the FDA regulation of 50 mg/kg for histamine content. Canning led to a substantial increase in total amines, with histamine being the predominant amine in most groups. Putrescine was present in all samples, with the highest levels found in canned tuna made from frozen yellow-fin tuna captured using drift gillnetting. Canned samples also exhibited higher cadaverine levels compared to raw tuna. Storage conditions, capture method, and tuna species were found to significantly affect tuna quality and biogenic amines formation.

Feasibility of Enzymatic Protein Extraction from a Dehydrated Fish Biomass Obtained from Unsorted Canned Yellowfin Tuna Side Streams: Part I.

This study presents for the first time a scalable process for the extraction of valuable proteins starting from samples of unsorted mixed tuna scraps which were previously dehydrated by an industrial patented process. The aims of this work were both to avoid the onerous sorting step of tuna leftovers, which generally consists of isolating skin and bones for collagen/gelatin extraction, and to improve the logistic of managing highly perishable biomass thanks to the reduction in its volume and to its microbiological stabilization. In view of a zero-waste economy, all the protein fractions (namely, non-collagenous proteins NCs and ALKs, gelatin, and hydrolyzed gelatin peptides, HGPs) isolated in the proposed single cascade flowchart were stabilized and preliminarily characterized. The extraction flowchart proposed allows one to obtain the following most promising compounds: 1.7 g of gelatin, 3.2 g of HGPs, and 14.6 g of NCs per 100 g of dehydrated starting material. A focus on oven-dried gelatin was reported in terms of proximate analysis, amino acid composition, color parameters, FT-IR spectrum, pH, and viscoelastic properties (5 mPa·s of viscosity and 14.3 °C of gelling temperature). All the obtained extracts are intended to be exploited in food supplements, feed, fertilizers/plant bio-stimulants, packaging, and the cosmetic industry.

UV-photochemical vapor generation coupled to hydride generation AAS in the study of dietary intake of Se, Hg, Cd, and Pb from fish

The consumption of fish by pregnant and lactating women is at the center of attention both from the point of view of ensuring healthy nutrition for fetal and neonatal development, and from the toxicological point of view. This research included a questionnaire survey on the frequency of fish consumption and the particular fish species consumed by 180 pregnant and lactating women in the Czech Republic, as well as the determination of Se, Hg, Cd, and Pb in the most commonly consumed species available on the Czech market. For this purpose, an analytical method for the determination of total selenium in biological samples using UV-photochemical vapor generation coupled to hydride generation atomic absorption spectrometry (UV-PVG-HG-AAS) was developed. This unique UV-photoreactor enables accurate and precise determination of Se with a detection limit of 0.007 mg/kg. Fish consumption by female respondents was generally low compared to the EU average. The determined Se contents in samples indicate a low intake of Se from fish in the Czech Republic; one third of the samples had Se contents below the detection limit. The highest Se contents were observed in the species Scomber scombrus, Sander lucioperca, and Thunnus albacares. The Hg content in fish samples did not exceed the EU maximum permissible values for mercury and methylmercury. The Tolerable Weekly Intake (TWI), which is 1.3 μg/kg of body weight per week, was not exceeded by any of the respondents. The maximum permissible value for Cd given by the European Commission was exceeded in the case of one sample of Scomber scombrus. Most of the samples had Cd content below the detection limit (0.002 mg/kg). The content of Pb in the analyzed samples was below the detection limit (0.013 mg/kg).

Effect of ocean circulation and chlorophyll-a concentration on yellowfin tuna catch rates in Sri Lankan logline fishery

Sri Lanka has access to fishery resources in the Indian Ocean due to its location. While traditional fishing methods are still used in the Sri Lankan fishery industry, modern technologies such as remote sensing and GIS are employed to determine spatiotemporal distribution of tuna fish resources in the offshore fishery industry. However, due to uncertain catch rates, Sri Lankan fishers report low catch per unit effort, leading to increased fishing duration to meet targeted catch. Potential fishing areas can be identified based on oceanographic conditions to reduce search time and improve efficiency, particularly for highly migratory species like yellowfin tuna. Therefore, this study is focused on identifying the impact of subsurface ocean currents and chlorophyll-a concentration on yellowfin tuna aggregations. The study analysed fishery and oceanographic data from January 2018 to December 2019 within a latitudinal range of 0°N to 20°N and a longitudinal range of 70°E to 90°E. The data were gridded at a resolution of 0.25 degrees and then matched for analysis. The generalized additive model (GAM) and the empirical cumulative distribution function (ECDF) were applied to identify the nature of relationships between CPUE and the oceanographic conditions. The results showed high tuna aggregations occurred in chlorophyll-a concentration between 0.3– 0.4 mg/m3 and current speed less than 0.4 m/s at a depth of 60 – 75 m of Sri Lankan longliners. Yellowfin tuna fishable aggregations were available throughout the year, although the spatial distribution of yellowfin tuna varied depending on the prevailing oceanographic conditions. Thus, searching for fishing locations based on oceanographic factors is essential for successful fishing operations. Hence, tuna harvest can be enhanced by maintaining fishing areas and the longline depth according to the oceanographic factors.

Lipid Correction for Carbon Stable Isotope Analysis of Yellowfin Tuna

Carbon stable isotopes (δ13C) are widely used in ecological studies to understand diet, food web dynamics, and movements of marine fishes. Still, δ13C is influenced by lipid content and often requires chemical extraction or mathematical correction. Here, we developed a species-specific mathematical lipid correction for white muscle tissue of yellowfin tuna (Thunnus albacares), a highly migratory finfish of considerable economic and ecological value. Lipid extraction was conducted on yellowfin tuna white muscle tissue (C:N range: 2.96–6.49), and both linear and non-linear lipid correction models for δ13C were fitted and assessed. Lipid extraction increased δ13C, and to a lesser extent, δ15N values in yellowfin tuna white muscle tissue, but had no effect on δ34S. Both non-linear models provided better fits to the data than the linear model, suggesting an asymptotic relationship between C:N and ∆δ13C. Results support the growing body of evidence that C:N ratios can be used to predict lipid corrected δ13C and highlight the value of mathematical correction approaches. We provide species-specific parameter estimates that can be used for lipid correction of white muscle tissue for δ13C analysis in yellowfin tuna and similar species for which species-specific models have yet to be developed.

Effects of foliar application of Fermented Fish Waste Solution from yellowfin tuna (<em>Thunnus albacares</em>) on growth and yield of MI-2 chilli (<em>Capsicum annuum</em>)

Yellowfin tuna is the most popular fish species consumed by Sri Lankans, and the majority of waste generated during processing is not utilized properly. The waste of this species has been identified as a rich source of amino acids and micro-nutrients which are essential for plant growth, but they are dumped into the ocean, or disposed in landfills leading to pollution. The study was conducted to prepare a fermented fish waste solution (FFWS) from yellowfin tuna and evaluate its efficiency on the growth and yield of MI-2 chilli crops. The FFWS solution was prepared by using fish waste from yellowfin tuna and jaggery in a 1:1 ratio and kept for about 21 days for fermentation in a cool and well-ventilated location. The filtrate of FFWS was applied separately as a foliar spray in different concentrations (2.5%, 5% and 7.5%) on chilli plants (n = 10 per treatment) once in a week with a negative control. The height of the plants, number of leaves and number of branches were measured, and the number of flowers and fruits were counted weekly until the first harvest. According to the findings, crops subjected to FFWS started flowering earlier and showed better growth and yield than control crops. Overall, plants treated with 5% and 7.5% of FFWS promoted growth and yield similarly, without significant differences. According to the research results, the application of the 5% FFWS is a more cost-effective and affordable choice than the application of the 7.5% FFWS. Further study and commercialization of FFWS foliar fertilizer may promote environmentally-friendly agriculture and the effective use of fish waste, as well as provide better solutions for the current scenario in Sri Lanka to reduce the usage of synthetic fertilizer.

Movement and vertical habitat use of yellowfin tuna Thunnus albacares in a vertically compressed habitat: the Galápagos Marine Reserve.

Tropical pelagic predators are exploited by fisheries and their movements are influenced by factors including prey availability, temperature, and dissolved oxygen levels. As the biophysical parameters vary greatly within the range of circumtropical species, local studies are needed to define those species' habitat preference and model possible behavioral responses under different climate change scenarios. Here, we tagged yellowfin tuna Thunnus albacares in the Galápagos Marine Reserve and tracked the horizontal and vertical movements of eight individuals for 4-97 days. The tuna traveled a mean of 13.6 km day-1 horizontally and dispersed throughout the archipelago and in offshore waters inside the Galápagos Marine Reserve and in the surrounding Ecuadorian exclusive economic zone. Vertically, they traveled a mean of 2 km day-1 , although high-resolution data from a recovered tag suggested that transmitted data underestimated their vertical movement by a factor of 5.5. The tracked yellowfin tuna spent most of their time near the surface, with an overall mean swimming depth of 24.3 ± 46.6 m, and stayed shallower at night (11.1 ± 16.3 m) than during the day ( 37.7 ± 60.9 m), but on occasion dived to cold, oxygen-poor waters below 200 m. Deep dives were commonly made during the day with a mean recovery period of 51 min between exposures to modeled oxygen-limiting conditions <1.5 mL L-1 , presumably to re-oxygenate. The depth and frequency of dives were likely limited by dissolved oxygen levels, as oxygen-depleted conditions reach shallow depths in this region. The main habitat of tracked yellowfin tunas was in the shallow mixed layer, which may leave them vulnerable to fishing. Vertical expansion of low-oxygen waters under future climate change scenarios may further compress their habitat, increasing their vulnerability to surface fishing gear.

Metal Load of Potentially Toxic Elements in Tuna (Thunnus albacares)-Food Safety Aspects.

The consumption of marine fishes has a positive effect on a consumer's health; however, it poses a potential risk due to their level of heavy metals in their body. Heavy metals can be naturally found in the environment, but their concentration can be increased with anthropogenic activities. Samples of tuna (Thunnus albacares) were collected at a fishery market. The potentially toxic elements (arsenic, cadmium, lead, and mercury) were determined with a validated method in the flesh of fish using inductively plasma optical emission spectrometry after microwave digestion. Generally, the average concentration of them was below the official limit values regulated by the European Union, except for lead. Based on the concentrations of arsenic (inorganic derivates: 0.05 ± 0.02 mg/kg) and cadmium (0.03 ± 0.01 mg/kg) in the tuna fish samples, and their calculated EDI values (As: 0.03-0.09 µg/kg/day; Cd: 0.05-0.07 µg/kg/day), the investigated food could be declared safe for human consumption. Generally, mercury content was below the official regulated limit, and the calculated EDI value was below the dietary reference value (0.3 μg/kg/day) in most of the samples (90%), exceeding it only in two samples (0.69 and 0.82 μg/kg/day); thus, they may not be harmful to the consumer. The concentration of lead above the official maximum limit (0.30 mg/kg) in 40% of tuna samples (0.30-1.59 mg/kg), as well as the exceeding of the dietary reference value for lead (adult: 0.16 μg/kg/day; children: 0.26 μg/kg/day) based on the calculated EDI values (0.28-1.49 μg/kg/day), draw attention to the importance of environmental pollution and the protection of consumers' health.

Study of the distribution of the catch of yellowfin tuna (Thunnus albacares) that was land at TPI (fish landing place) Ulee Cot, Meuraxa District, Banda Aceh City

Activities at fishing port greatly affect the process of distributing catches, especially the distribution of yellowfin tuna at TPI Ulee Cot. Distribution activities have not been optimal and have hampered the distribution flow. This is due to the slow process of handling fish and the incomplete facilities. The length of the distribution process will determine the quality of the product to be marketed. This study aims to describe the distribution activities of the catch landed at TPI, the condition of fishing facilities and relation to the distribution of yellowfin tuna. The data taken consisted of the handling of the catch, pattern, transportation, price, the fishing unit and TPI facilities distribution from interviews and questionnaires. Data analysis is carried out into data selection, data appearance, and drawing conclusions. Distribution activities start from fish transportation and fish handling from boats to fish transported into trucks to be distributed to destination area. The distribution pattern at TPI Ulee Cot only consists of one distribution pattern starting from the level of fishermen-exporting companies. The lack of cold storage facilities causes the quality of the catch to decrease because the fish are not immediately removed from the hold ship until the truck came.

A fast and non-invasive imaging procedure to fight red tuna fraud

Recently, a food fraud regarding tuna samples has been detected in Europe. Some batches of tuna treated with illegal adulterants like vegetable extracts, including beetroot, were detected after several cases of food poisoning. This paper proposes a new fast and non-destructive technique based on smartphone imaging which contributes to the fight against tuna fraud. The color of different samples of three species of tuna (Thunnus thynnus, Thunnus albacares and Thunnus obesus) has been analyzed by a colorimetrically characterized smartphone. Descriptive analysis of the samples shows that different species of tuna can be grouped by their color in CIELAB space, and that samples adulterated with beetroot extracts can be detected by the proposed image processing procedure. A logistic regression model was implemented to distinguish between real and fraudulent samples, and its suitability checked by k-folding cross validation (n = 189), achieving a 0.59% false positive rate with a 10% false negative rate.

Operasi penangkapan dan penanganan hasil tangkapan pole and line KM Sari Usaha 09

The utilization of marine biological resources in an effort to increase the production of fishery products has always received serious attention from fishing stakeholders. One of the fishing gear used in exploiting fish resources is pole and line. This study aims to examine pole and line fishing operations and methods of handling the catch on board. This factorrs are important in increasing production with maintained fish quality. This research is descriptive in nature and data collection includes primary data obtained directly from the source or research object, and secondary data obtained indirectly from the research object. Fishing operations include preparation activities, especially ship documents, fishing gear, food supplies, fuel and ice blocks. The operation of pole and line fishing gear uses live bait as a determining factor for fishing success. The types of fish caught are skipjack tuna, yellow fin tuna, dolphinfish, and rainbow runner. The steps taken in the process of handling caught fish on board include preparing catch handling equipment, handling freshly caught fish, and handling fish in holds.

Studi teknis dan kelayakan usaha kapal Pole and Line

The purpose of this study is to understand the technical aspects of fishing using the pole and line method, as well as to analyze the feasibility of the pole and line fishery. The research method used in this study is descriptive with a quantitative approach, conducted at PT Sari Usaha Mandiri, specifically on KM Sari Usaha 09, with a vessel specification of 25.73 m in length, 5.16 m in width, and 2.60 m in height. The components of the pole and line gear are a rod, a fishing line, and a hook. The fishing operation also involves the use of fish aggregating devices, which requires compliance with sea safety, fishing regulations, and storage requirements. The fishing technique employed is known as "banting," with the main catches being skipjack tuna and yellowfin tuna. The fishing area is located in the WPPN-RI 715. Based on the feasibility analysis, it can be concluded that the pole and line fishery is viable for business because the net benefit cost ratio is &gt; 1 (1.097), the production output (351,600 kg) and revenue (IDR 6,328,800,000) exceed the break-even point of production (77,650 kg) amounting to IDR 1,397,704,483. The margin of safety is IDR 4,931,095,517 or 78%, the net present value is &gt; 0 (IDR 3,485,024,022), the internal rate of return is &gt; 5% (86%), and the payback period is 2.3 years.

Deep learning for automated fish grading

Fish is a staple food around the globe, and its quality is heavily dependent on freshness. The conventional method for evaluating the quality of fish is through a visual inspection of a sample. However, this approach heavily depends on human senses for precise assessment, leading to a susceptibility to variability in accuracy and efficiency. Moreover, the potential for safety to be compromised due to errors in the evaluation process makes it a less reliable method. This work presents two Neural Network (NN) architectures, FishNET-S and FishNET-T, to evaluate the quality of the Indian Sardinella and the Yellowfin Tuna, respectively, using RGB images captured from smartphone cameras. The FishNET-S is based on the VGG-16 with the introduction of a Block Attention Module (BAM) to drive the network towards learning the features related to fish quality evaluation from the eye region of the entire fish. In contrast, the FishNET-T architecture first performs a color decomposition based on hue, saturation, and intensity transformations before forwarding the hue and saturation components to the CNN in order to effectively identify grades through fish meat. Experimentally, FishNET-S has managed to obtain an accuracy of 84.1%, while FishNET-T yielded an accuracy of 68.3%. The comparison analysis carried out with the use of generic machine learning and state of the art deep learning models shows that the performance of the proposed novel architectures is dominant and unchallenged.

Climate change to drive increasing overlap between Pacific tuna fisheries and emerging deep-sea mining industry

In ocean areas beyond national jurisdiction, various legal regimes and governance structures result in diffused responsibility and create challenges for management. Here we show those challenges are set to expand with climate change driving increasing overlap between eastern Pacific tuna fisheries and the emerging industry of deep-sea mining. Climate models suggest that tuna distributions will shift in the coming decades. Within the Clarion-Clipperton Zone of the Pacific Ocean, a region containing 1.1 million km2 of deep-sea mining exploration contracts, the total biomass for bigeye, skipjack, and yellowfin tuna species are forecasted to increase relative to today under two tested climate-change scenarios. Percentage increases are 10–11% for bigeye, 30–31% for skipjack, and 23% for yellowfin. The interactions between mining, fish populations, and climate change are complex and unknown. However, these projected increases in overlap indicate that the potential for conflict and resultant environmental and economic repercussions will be exacerbated in a climate-altered ocean. This has implications for the holistic and sustainable management of this area, with pathways suggested for closing these critical gaps.

Climate Change Potential Impacts on the Tuna Fisheries in the Exclusive Economic Zones of Tonga

The potential impacts of climate change on the distribution of tuna in Pacific Island countries’ exclusive economic zones have yet to be investigated rigorously and so their persistence and abundance in these areas remain uncertain. Here, we estimate optimal fisheries areas for four tuna species: albacore (Thunnus alalunga), bigeye (Thunnus obesus), skipjack (Katsuwonus pelamis), and yellowfin (Thunnus albacares). We consider different climate change scenarios, RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5, within a set of tuna catch records in the exclusive economic zone of Tonga. Using environmental and CPUE datasets, species distribution modelling estimated and predicted these fisheries areas in the current and future climatic scenarios. Our projections indicate an expansion in area and a shift of productive areas to the southern part of this exclusive economic zone of Tonga. This is an indication that future climatic scenarios might be suitable for the species under study; however, changes in trophic layers, ocean currents, and ocean chemistry might alter this finding. The information provided here will be relevant in planning future national actions towards the proper management of these species.

Development of leather from the skin of yellowfin tuna (&lt;em&gt;Thunnus albacares&lt;/em&gt;) and Asian sea bass (&lt;em&gt;Lates calcarifer&lt;/em&gt;) using an environmentally friendly tanning technique

Yellowfin tuna (Thunnus albacares) and Asian sea bass (Lates calcarifer) are highly demanded export fish species in Sri Lanka. The objective of the present study was to prepare leather from the skin of T. albacares and L. calcarifer using tanning media prepared with black tea (Camellia sinensis) powder and table salt (NaCl). Black tea powder and table salt concentrations were increased by 10 grams (initial weight; 10 gL-1) and 1 gram (initial weight; 1 gL-1), respectively each day for 12 d. Skins were dipped in each concentration for 24 hrs. After additional water was removed, vegetableoil-applied skins were stretched and air-dried at room temperature. The percentage of ash, fat,protein, and tensile strength of the leather prepared from L. calcarifer skin was significantly higher(P&lt;0.05) compared to leather prepared from T. albacares skin. The percentage of moisture, averagethickness, and tear strength of the leather prepared from the T. albacares skin were significantlyhigher (P&lt;0.05) than the leather prepared from L. calcarifer skin. According to the ΔL*, Δa*, andΔb* values, leather prepared from T. albacares skin has lighter, greener, bluer and L. calcarifer skinhas darker, greener, yellower colours respectively. There are no significant colour differences betweenprepared leathers (P&gt;0.05). Sensory evaluation results indicated that, finishing, appearance,handling, and overall acceptability, of leather wallet prepared from T. albacares has higherconsumer acceptance. The study demonstrated the effectiveness of this novel method for preparationof leather from T. albacares and L. calcarifer skin. In conclusion, T. albacares skin is more suitablefor fish leather preparation using the above described tanning method.