Proximate analysis of the flesh and anatomical weight composition of skipjack tuna (Katsuwonus pelamis)
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Skipjack tuna
Flesh
Proximate
Over the past several decades,impacts of climate changes on the sustainable development of marine fisheries have been greatly concerned,especially the global warming. Tuna fisheries play a significant role in marine fisheries not only due to their high economic values,but also because of their abundant captures. In tuna fisheries,catches of skipjack tuna( Katsuwonus pelamis) had accounted for more than half of the total captures since 2005. However,studies on responses of skipjack tuna to climate change are still on the very beginning currently. Therefore,the paper reviewed the trend in captures of skipjack tuna over the past six decades,and compared the study histories on skipjack tuna under climate change between Chinese scientists and international scientists. Moreover,based on our current research status,we proposed our perspectives on the future concentrations on skipjack tuna.
Skipjack tuna
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Fishery for tuna and tuna like fishes in the country have been in vogue from time immemorial and presently involve fishery by coastal based fleets of varying specifications with different craft-gear combinations and longline fishery by large oceanic fishing vessels. The former undertake short duration fishing trips and exploit mainly surface tunas in the outer shelf and adjacent oceanic waters. The tuna landings though nominal during 1950-2005, registered a continuous increase over the years from a minimum of 848 t (1951) to 46,334 t (2000). With the introduction of targeted fishing for oceanic tunas during 2005-‘06, the landings improved and reached the maximum of 129,801 t in 2008. The fishery was supported by nine species, five coastal/neritic species and four oceanic species. Coastal tunas formed 57% of the tuna catch during 2006-’10 and was represented by the little tuna ( Euthynnus affinis ), frigate tuna ( Auxis thazard ), bullet tuna ( Auxis rochei ), longtail tuna ( Thunnus tonggol ) and bonito ( Sarda orientalis ). The oceanic species, which formed 43% of tuna catch, were yellowfin tuna ( Thunnus albacares ), skipjack tuna ( Katsuwonus pelamis ), dogtooth tuna ( Gymnosarda unicolor ) and bigeye tuna ( Thunnus obesus ). Information collected from different sources suggested that longliners operating in Indian EEZ and adjacent international waters caught around 87,000 t of tune annually during 2006-'10. Catch was supported by three species dominated by yellowfin tuna and small proportion of big-eye and dogtooth tuna. Since, fishery by coastal based units restricted to small areas and share of the catch by long liners from EEZ are not clearly known, systematic assessment of tuna stock in Indian EEZ is very difficult. However, the evaluation of the fishery scenario indicated only limited scope for improving tuna production from certain areas of coastal waters; whereas enormous scope remain for increasing tuna production from the oceanic waters of EEZ. However, since tunas being straddling resources shared by several nations, exploitation at one area will influence the fishery in other areas.
Yellowfin tuna
Thunnus
Skipjack tuna
Albacore
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Yellowfin tuna
Skipjack tuna
Thunnus
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Abstract Yellowfin tuna ( Thunnus albacares ), mackerel tuna ( Euthynnus affinis ), and skipjack tuna ( Katsuwonus pelamis ) have important economic values for the capture fisheries in Indonesia. Activities of identifying these fish and other types of tuna have been done manually, which can lead to errors and ultimately affect statistics, stock estimates, or traceability. The aim of this research is to use deep learning methods in identifying three species of tuna, specifically yellowfin tuna, mackerel tuna, and skipjack tuna. YOLO’s newest model, YOLOv5, was used to identify the fish. The number of epochs that produces the optimum accuracy value for use in the YOLOv5 model is 400. The values for training loss, accuracy, precision, recall and F1-Score when the model is learning with a total of 400 epochs are 0.000253, 95%, 98.1%, 93.9%, and 96%. Based on these results, the three species of tuna can be identified with high accuracy.
Yellowfin tuna
Skipjack tuna
Thunnus
Scombridae
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Tuna longlining is an important Taiwanese offshore fishery. Knowledge of longlining fishing efficiency is essential for providing fisheries management options. A total of 42 sampling vessels were selected from Nanfangao, Donggang, and Xingang fishing harbors during 29 November 1998 to 15 June 2003. The longlining fishing grounds was significantly different among the three harbors. The eastern waters off Taiwan were the major fishing ground during spring and summer, longliners then transferred to the South China Sea during autumn and winter. If all captures were categorized into tuna/tuna-like and non-tuna species, longliners from Nanfangao and Xingang caught mostly non-tuna dolphinfish whereas Donggang longliners caught mainly yellowfin tuna. There was a positive correlation between vessel tonnages and the longest distance of fishing. Larger longliners would catch larger tuna/tuna-like species with lower catch rate. There was no significant difference of the catch rate between the daytime and nighttime setting for tuna/tuna-like species, but it had significant difference for non-tuna species. The moonfish was the best baits in catching yellowfin tuna, blue marlin, black marlin, sailfish and dolphinfish. The milkfish was useful to catch bluefin tuna. Using mackerels as baits might be more effective in catching sharks or squid as baits would obtain better catch rates for tunas.
Yellowfin tuna
Swordfish
Bycatch
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For the effective utilization of tuna processing byproducts such as roes of skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacores) as a food resource, the roes of skipjack and yellowfin tuna were examined on food component characteristics and also compared to those of Alaska pollack (Theragra chalcogramma). The concentrations of heavy metal in both roe of the skipjack and yellowfin tuna were below the reported safety limits, therefore, these roes appeared to be safe as a raw material for food resource. The contents of crude protein were 21.4% in the skipjack tuna roe and 21.5% in the yellow fin tuna roe, which showed to be the major component in tuna roes. The prominent amino acids of total amino acids were aspartic acid, glutamic acid, leucine and lysine, and these amino acids were comprise to be 38.4-41.2% of total amino acid in both tuna roes. The total lipid content were 2.1 % in the skipjack tuna roe and 2.0% in the yellofin tuna roe. The major component of total lipid was found to be triglyceride in both tuna roes (skipjack tuna roe, 93.3%; yellow fin tuna roe, 92.0%), which was high in the compositions of 16:0, l8:1n-9, and 22:6n-3. The content of DHA in total lipid of the tuna roes (skipjack tuna roe, 29.9%; yellowfin tuna roe, 36.3%) were higher than that of Alaska pollack roe (18.1%). Based on the results of the proximate composition, mineral, amino acid and lipid characteristic, roes of skipjack tuna and yellowfin tuna showed potential as a raw material for food.
Yellowfin tuna
Skipjack tuna
Thunnus
Scombridae
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Overfishing
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An ultrasonic tagging program for tuna was conducted in 1988 and 1989 within the Regional Tuna Project of the Indian Ocean Commission. Three yellowfin and six skipjack tuna were tagged with temperature or depth sensitive transmitters in the North-western part of the Mozambique Channel (12°S-44°E) around Anjouan island (Comoros Archipelago) where several fish aggregating devices (FADs) were previously moored. The horizontal and vertical movements observed during 8 tracks (3 yellowfin and 5 skipjack tuna) whose duration was between 3 and 24 hours, are analysed in terms of swimming depth, temperature encountered and position of the tracked tuna relative to the FAD or coast line. Comparison between recorded depth of tracked tuna and echo sounded fish indicated tracked tuna were schooling. Two of the 3 tagged yellowfin tuna displayed a behaviour of association with FADs. The optimal distance between 2 anchored FADs, to avoid adverse interference in the attraction of tuna, is estimated as 11 nautical miles. A very small percentage of time is spent by yellowfin tuna near the surface. The mean swimming depths encountered in the daytime by yellowfin tuna are much deeper (70-110 m) than they are at night (40-70 m). The relative homogeneity in the observed behaviour of yellowfin tuna and the fair general agreement with previous results obtained in the Pacific Ocean, should allow application of ultrasonic tagging results to fishing and prospecting purposes in the future. The movements of the 5 tracked skipjack tuna do not indicate a behavioural association with FADs, and do not present marked differences between the swimming depths encountered by night and during the daytime. The high variability observed in the behaviour of the different tracked skipjack tuna, and the bad agreement with previous results obtained in the Atlantic and in the Pacific Oceans have to be emphasized. A high turnover of the skipjack tuna concentrated around FADs due to an intense and pelmanent migratory flow through the area of Comoros Islands could partly explain these apparent discrepancies.
Yellowfin tuna
Skipjack tuna
Thunnus
Scombridae
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