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"yellowfin tuna"
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Using Remote-Sensing Environmental and Fishery Data to Map Potential Yellowfin Tuna Habitats in the Tropical Pacific Ocean
Changes in marine environments affect fishery resources at different spatial and temporal scales in marine ecosystems. Predictions from species distribution models are available to parameterize the environmental characteristics that influence the biology, range, and habitats of the species of interest. This study used generalized additive models (GAMs) fitted to two spatiotemporal fishery data sources, namely 1° spatial grid and observer record longline fishery data from 2006 to 2010, to investigate the relationship between catch rates of yellowfin tuna and oceanographic conditions by using multispectral satellite images and to develop a habitat preference model. The results revealed that the cumulative deviances obtained using the selected GAMs were 33.6% and 16.5% in the 1° spatial grid and observer record data, respectively. The environmental factors in the study were significant in the selected GAMs, and sea surface temperature explained the highest deviance. The results suggest that areas with a higher sea surface temperature, a sea surface height anomaly of approximately −10.0 to 20 cm, and a chlorophyll-a concentration of approximately 0.05–0.25 mg/m3 yield higher catch rates of yellowfin tuna. The 1° spatial grid data had higher cumulative deviances, and the predicted relative catch rates also exhibited a high correlation with observed catch rates. However, the maps of observer record data showed the high-quality spatial resolutions of the predicted relative catch rates in the close-view maps. Thus, these results suggest that models of catch rates of the 1° spatial grid data that incorporate relevant environmental variables can be used to infer possible responses in the distribution of highly migratory species, and the observer record data can be used to detect subtle changes in the target fishing grounds.
Journal Article
The Impact of Acute Ammonia Nitrogen Stress on the Gill Tissue Structure and Antioxidant Ability of Gills and Red and White Muscle in Juvenile Yellowfin Tuna (Thunnus albacares)
To explore the impacts of acute ammonia nitrogen (NH3-N) stress on gill structure and the antioxidant ability of red and white muscles in juvenile yellowfin tuna (Thunnus albacares), this study used natural seawater as a control, establishing two experimental NH3-N groups at 5 and 10 mg/L. Gills and red and white muscle were taken at 6, 24, and 36 h for the determination of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GHS-PX) levels, and to observe gill structure. The results indicated that, with increasing time, the MDA concentration and CAT activity in the gills of the 5 mg/L group showed a trend of first increasing and then decreasing, while SOD activity exhibited a downward trend. In the 10 mg/L group, MDA concentration showed an increasing trend, while SOD, CAT, and GSH-PX activities demonstrated a trend of first increasing and then decreasing. In the 5 mg/L group, the MDA concentration and GSH-PX activity in the red muscle showed an increasing trend. In the 10 mg/L group, MDA concentration and SOD and CAT activities exhibited a downward trend. In the 5 mg/L group, the MDA concentration and SOD activity in the white muscle showed a downward trend, while CAT activity exhibited an increasing trend. In the 10 mg/L group, MDA concentration and CAT activity demonstrated a trend of first increasing and then decreasing, while SOD activity showed a downward trend. Ammonia nitrogen can lead to necrosis and shedding of gill epithelial cells, cell vacuolation, edema, as well as proliferation, hypertrophy, and fusion of secondary lamellae. This study demonstrates that NH3-N can alter gill structure and reduce the antioxidant ability of gills and red–white muscle. The findings provide scientific data that can support the aquaculture and recirculating aquaculture systems of juvenile tuna.
Journal Article
Biochemical Changes Occurring in Yellowfin Tuna Eggs during Embryonic Development
Changes in nutritional constituents and enzyme activities were clarified in yellowfin tuna (YFT, Thunnus albacares) eggs during embryonic development, from eggs immediately after fertilization to hatching. The protein levels in the eggs gradually increased with development until the completion of hatching. In contrast, the triglyceride (TG) and free amino acid (FAA) levels in the eggs gradually declined with embryonic development until hatching was complete, although the energy composition of the FAAs was lower than that of the TGs throughout embryonic development. These results indicate that endogenous TGs are preferentially expended as an energy source during embryonic development. Overall, changes in the activities of aspartate aminotransferase, alanine aminotransferase, creatine kinase, and alkaline phosphatase showed similar patterns throughout development. First, the enzyme levels diminished; then, they remained at constant, low levels just before hatching, when they rapidly increased. This rapid increase was consistent with the protein content, suggesting that organ differentiation and functionalization were promoted during this period. These results will contribute to the establishment of mass-seeding production of YFT.
Journal Article
Modelling the spatial distribution of the yellowfin tuna, Thunnus Albacares in the Persian Gulf using a fuzzy rule-based classification
Yellowfin tuna, Thunnus albacares, are the most important ecological and economic fishes in the Persian Gulf. In recent decades, their populations have faced overfishing, environmental problems and climate change. In this study, using some environmental variables affecting the habitat of tuna fish, i.e. sea surface temperature at night and day, reflection of 645 nm wavelength as a water turbidity, angstrom view of aerosol 443 to 965 nm, aerosol optic thickness at 869 nm, organic and inorganic particle carbon, photosynthetic active radiation, absorption by phytoplankton at 443 nm and chlorophyll-a concentration from 2002 to 2018, on the spatial distribution of yellow-fin tuna has been modelled by fuzzy rule-based classification. Over the years, the variables had different degrees of importance in the models. There was a great variation in the spatial distribution of the species from year to year.
Journal Article
Development of loop-mediated isothermal amplification in commercial fish products
Tuna is one of the most widely consumed fish on the European market, being available in various consumable options. Among them, Thunnus albacares, also called yellowfin tuna, is a delicacy and is consumed by millions of people around the world. Due to its comparatively high cost and demand, it is more vulnerable to fraud, where low-cost tuna or other fish varieties might be replaced for economic gain. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed and validated for targeting the mitochondrial cytochrome b gene for fast and direct detection of Thunnus albacares, which is a valuable tuna species. The analytical specificity was confirmed using 18 target samples (Thunnus albacares) and 18 samples of non-target fish species. The analytical sensitivity of the LAMP assay was 540 fg DNA per reaction. In addition, a simple and direct swab method without time-consuming nucleic acid extraction procedures and the necessity for cost-intensive laboratory equipment was performed that allowed LAMP detection of Thunnus albacares samples within 13 minutes. Due to its high specificity and sensitivity, the LAMP assay can be used as a rapid and on-site screening method for identifying Thunnus albacares, potentially providing a valuable monitoring tool for food authenticity control by the authorities.
Journal Article
Development of loop-mediated isothermal amplification
Tuna is one of the most widely consumed fish on the European market, being available in various consumable options. Among them, Thunnus albacares, also called yellowfin tuna, is a delicacy and is consumed by millions of people around the world. Due to its comparatively high cost and demand, it is more vulnerable to fraud, where low-cost tuna or other fish varieties might be replaced for economic gain. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed and validated for targeting the mitochondrial cytochrome b gene for fast and direct detection of Thunnus albacares, which is a valuable tuna species. The analytical specificity was confirmed using 18 target samples (Thunnus albacares) and 18 samples of non-target fish species. The analytical sensitivity of the LAMP assay was 540 fg DNA per reaction. In addition, a simple and direct swab method without time-consuming nucleic acid extraction procedures and the necessity for cost-intensive laboratory equipment was performed that allowed LAMP detection of Thunnus albacares samples within 13 minutes. Due to its high specificity and sensitivity, the LAMP assay can be used as a rapid and on-site screening method for identifying Thunnus albacares, potentially providing a valuable monitoring tool for food authenticity control by the authorities.
Journal Article
Yellowfin tuna
Yellowfin tuna (YFT, Thunnus albacares) is a commercially important species targeted by fisheries in the Gulf of Mexico (GM). Previous studies suggest a high degree of residency in the northern GM, although part of the population performs movements to southern Mexican waters. Whether YFT caught in southern waters also exhibit residency or migrate to the northern gulf is currently uncertain, and little is known regarding their trophic ecology. The isotopic composition (bulk & amino acids) of YFT muscle and liver tissues were compared to a zooplankton-based synoptic isoscape from the entire GM to infer feeding areas and estimate Trophic Position (TP). The spatial distribution of [delta].sup.15 N.sub.bulk and [delta].sup.15 N.sub.Phe values of zooplankton indicated two distinct isotopic baselines: one with higher values in the northern GM likely driven by denitrification over the continental shelf, and another in the central-southern gulf, where nitrogen fixation predominates. Based on the contribution of the two regional isotopic baselines to YFT tissues, broad feeding areas were inferred, with a greater contribution of the northern GM (over a one-year time scale by muscle), and to a lesser extent in the central-southern GM (over the ca. 6-month scale by liver). This was corroborated by similarities in [delta].sup.15 N.sub.Phe values between YFT and the northern GM. TP estimates were calculated based on stable isotope analysis of bulk (SIA) and compound-specific isotope analysis (CSIA-AA) of the canonical source and trophic amino acids. Mean TP based on SIA was 4.9 ± 1.0 and mean TP based on CSIA-A was 3.9 ± 0.2. YFT caught within the Mexican region seem to feed in northern and in central and southern GM, while feeding in the northern GM has a temporal component. Thus, management strategies need to consider that YFT caught in US and Mexican waters are a shared binational resource that exhibit feeding migrations within the GM.
Journal Article
The Battle for Paradise
CORRECTION: Regarding the book, T he Battle for
Paradise by Jeremy Evans, the following correction has been
made on page 163 in paragraph three (3) to wit: \"Weston once worked
in concert with government officials in a pre-planned sting
operation, complete with marked bills: Weston, whose role in the
operation involved paying a bribe to the Golfito mayor for a
concession and then documenting the bribe as a way to expose the
mayor as a corrupt government official, was a former cocaine
dealer, according to Dan, and someone who illegally acquired
possession of his sawmill property.\" Pavones, a town located on the
southern tip of Costa Rica, is a haven for surfers, expatriates,
and fishermen seeking a place to start over. Located on the Golfo
Dulce (Sweet Gulf), a marine sanctuary and one of the few tropical
fjords in the world, Pavones is home to a legendary surf break and
a cottage fishing industry. In 2004 a multinational company
received approval to install the world's first yellowfin tuna farm
near the mouth of the Golfo Dulce. The tuna farm as planned would
pollute the area, endanger sea turtles, affect the existing fish
population, and threaten the world-class wave. A lawsuit was filed
just in time, and the project was successfully stalled. Thus began
an unlikely alliance of local surfers, fishermen, and global
environmental groups to save a wave and one of the most biodiverse
places on the planet. In The Battle for Paradise , Jeremy
Evans travels to Pavones to uncover the story of how this ragtag
group stood up to a multinational company and how a shadowy figure
from the town's violent past became an unlikely hero. In this
harrowing but ultimately inspiring story, Evans focuses in turn on
a colorful cast of characters with an unyielding love for the ocean
and surfing, a company's unscrupulous efforts to expand profits,
and a government that nearly sold out the perfect wave.
eBook
Depth and temperature preferences of meagre, argyrosomus regius, as revealed by satellite telemetry
Argyrosomus regius (commonly referred to as meagre), is one of Europe’s largest coastal bony fish species and supports important recreational and commercial fisheries in the Atlantic and Mediterranean coasts. Demand for this species, and more recently for their swim bladders, has led to regional population declines and growing importance as an aquaculture species. Despite intense research in captivity, little is known about the spatial ecology of A . regius ’s wild population, including basic information such as vertical migrations and depth/temperature preferences. Previous research based on indirect data suggests a seasonal habitat shift from shallow to deeper waters, but this has never been validated through direct high-resolution movement data. In this study, we tagged 13 adult A . regius with pop-up satellite archival tags in the South of Portugal, which successfully returned data from 11 individuals including high-resolution data from six recovered tags (mean, range: 167 days, 28–301 days). We found that adults of this population spend 95.2% of their time between 5 and 75 m depth (mean ± SD, 30.9m ± 18.3m) and do not venture beyond 125 m. Across seasons, A . regius move across water temperatures between 13.3 and 24.8°C with a preferred thermal range between 14 and 18°C where they spent 75.4% of their time. The inferential modelling using this electronic data validated previous hypotheses by showing significant differences between a shallower and warmer summer habitat vs. a deeper and cooler winter habitat. Visual investigation of the diel effects on depth preferences suggests subtle changes in depth use between day and night during the warmer months of the year. We speculate that these patterns are in response to the species’ behavioural ecology and physiology, reflecting the seasonal changes in water stratification and presence of prey, as well as on the species reproduction, which results in summer spawning aggregations in shallower areas.
Journal Article