Search Results (61)

Mercury (Hg) is a global health concern due to its prevalence, persistence, and toxicity. Numerous studies have assessed Hg concentrations in seafood, but variability in reported concentrations highlights the need for continued monitoring and stricter regulations. We measured total Hg (tHg) in 148 pre-processed, packaged seafood products purchased in Raleigh, North Carolina, using thermal decomposition–gold amalgamation atomic absorption spectrophotometry. Products were grouped into three categories based on trophic ecology and physiology: (1) tuna, (2) other bony fish, and (3) shellfish and squid. Among tuna, albacore had the highest average tHg (396.4 ng/g ± 172.1), while yellowfin had the lowest (68.3 ng/g ± 64.7). Herring (54.0 ng/g ± 23.2) and crab (78.2 ng/g ± 24.1) had the highest concentrations in the other two groups. One can of albacore exceeded the FDA action level of 1 part per million (1.3 ppm or 1300 ng/g). Brand differences were significant for both albacore and light tuna, with Brand 1 consistently showing higher Hg levels. Comparisons to FDA data (1990–2012) suggest Hg concentrations in tuna have remained stable over the past two decades. This study underscores the variability of Hg concentrations across species and brands and the need for continued monitoring to protect consumers. Full article

Psychrotrophic Morganella spp. is a typical histamine producer commonly found in seafood, exhibiting a high histamine-producing capacity. In this study, two strains of Morganella (GWT 902 and GWT 904) isolated from yellowfin tuna were subjected to phenotypic and genotypic characterization. Phenotypic analysis reveals differences in growth temperature, NaCl tolerance, and D-galactose fermentation capacity between the two strains. Notably, the histamine production capacity of GWT 902 is significantly higher than that of GWT 904 at 4 °C. The complete genome sequences of strains GWT 902 and GWT 904 were sequenced, identifying GWT 902 as Morganella psychrotolerans and GWT 904 as Morganella morganii subsp. sibonii. Genomic analysis confirms the presence of histidine decarboxylase gene clusters (hdcT1, hdc, hdcT2, hisRS) in both strains, and sequence alignment shows that the amino acid sequence similarity of histidine decarboxylase encoded by the hdc gene was 95.24%. Gene function analysis further identified genes associated with putrescine biosynthesis, sulfur metabolism, lipase and protease secretion, and detected key genes in quorum sensing (QS), stress adaptation, and antibiotic resistance. This study provides valuable insights into the taxonomic analysis of psychrotrophic Morganella spp. and contributes to the development of efficient strategies for preventing histamine formation in seafood. Full article

Epipelagic fish communities dominate fish assemblages and are an important part of marine ecosystems due to their high abundance, vertical migration behavior, and global distribution. Purse seine fisheries are key components of marine fisheries in the tropical Western and Central Pacific Ocean (WCPO), primarily targeting skipjack tuna (Katsuwonus pelamis, SKJ), yellowfin tuna (Thunnus albacares, YFT), and bigeye tuna (Thunnus obesus, BET). In this study, WCPO purse seine fishery data from 2014 to 2022, combined with environmental factor data, were used, and Mantel tests and correlation analysis were employed to analyze the diversity, fish coexistence mechanisms, and environmental responses of catch communities under the following two different fishing strategies: free–swimming schools (FSCs) and drifting fish aggregating devices (DFADs). Mantel tests indicated that nitrate (NO_3⁻), the Oceanic Niño Index (ONI), and pH significantly impact the diversity of the FSCs community, whereas NO_3⁻ significantly affects the diversity of the DFADs community. Based on the correlation analysis results, in the FSCs community, yellowfin tuna was positively correlated with bigeye tuna, and yellowfin tuna was negatively correlated with skipjack tuna and black marlin (Istiompax indica, BLM). In the DFADs community, yellowfin tuna was only positively correlated with skipjack tuna and bigeye tuna. In addition, species with high correlations were also positively correlated. The results of this study provide a theoretical basis for the biodiversity conservation of catch communities under two different purse seine fishing strategies in the WCPO. Full article

The mercury (Hg) present in ocean fish has caused concern regarding the effects of maternal consumption on child outcomes but it is now recognized that mothers that eat more ocean fish during pregnancy have children with higher social, scholastic, and IQ scores. These findings coincide with the current understanding of the mechanism of Hg toxicity which indicates ocean fish consumption will prevent rather than cause harm. High-Hg exposures sequester selenium (Se) and inhibit Se-dependent enzymes that prevent and reverse oxidative damage in the brain and support fetal brain development. However, aside from certain types of shark and other apex marine predators, seafood contains more Se than Hg and thus counteracts instead of contributing to Hg toxicity. This study evaluates the Hg and Se present in bigeye tuna, yellowfin tuna, albacore tuna, skipjack, swordfish, striped marlin, blue marlin, spearfish, mahimahi, wahoo, monchong, escolar, mako shark, and thresher shark to establish their health benefit values (HBVs). Positive HBVs (0.3–19.6), indicating a molar excess of Se over Hg, were found in 14 of the 15 species studied. Only mako shark uniformly contained Hg in excess of Se to produce a negative HBV (−16.4), indicating its consumption should be minimized during pregnancy. Full article

The large pelagic species play an important role in transferring energy in vast distant marine ecoregions. Results obtained report on extraordinary findings of important commercial species in southeast–south Brazilian waters, including the Southern bluefin tuna Thunnus maccoyii and the Pacific bluefin tuna Thunnus orientalis, an endemic species from the Pacific Ocean. These specimens were identified within the genomic description of 10 individuals randomly selected from the catch to evaluate the catch composition of pelagic longline fisheries off Brazilian waters. Most of the records were from T. maccoyii (6), followed by the Bigeye tuna T. obesus (2), Yellowfin tuna T. albacares (1), and T. orientalis (1). Yellowfin and Bigeye tuna are expected to be captured in the vicinity of the longline fishing areas. However, the unlikely presence of the cold-water T. maccoyii and the warm-water T. orientalis suggests a long migration from common species ranges that could be influenced by climate change. These results imply a readjustment of spatial management structures for these species. Full article

Environmental temperature declines significantly impact the physiological processes of marine organisms, particularly under the cool La Nina conditions, challenging yellowfin tuna (Thunnus albacares) aquaculture. Low temperatures affect fish metabolism and immune functions and can alter the gut microbiota composition, influencing health and growth. This study investigates the impact of low temperatures on the gut microbiota of juvenile yellowfin tuna. Fish were divided into a Low Temperature (LT) group (24 °C), an Ultra Low Temperature (ULT) group (18 °C), and a Control group (CG) (30 °C), with evaluations at 0, 12, 24, and 36 h using α-diversity analysis and microbial species composition. Results indicated a significant increase in the Ace index for the ULT group after 36 h of cold stress (p < 0.05), with no significant changes in the Shannon index. A decline in Proteobacteria and increases in Verrucomicrobiota and Firmicutes were observed in both LT and ULT groups. Additionally, both LT and ULT groups showed a significant rise in the Ace index at 36 h (p < 0.05), with a significant decrease in the Shannon index in the ULT group at 24 h. Furthermore, Firmicutes significantly increased at 12 h in both temperature groups (p < 0.05). These findings highlight the potential role of the gut microbiome in adapting yellowfin tuna to cold environments and provide microbial insights into their physiological adaptations, laying a foundation for further research and practical applications in aquaculture under cold conditions. Full article

Fisheries and aquaculture play a crucial role in global food security, yet species mislabeling remains a persistent challenge, undermining consumer trust and market transparency. Proper food labeling is essential for protecting public health due to the presence of unknown toxic or allergenic substances and preventing illegally sourced products from entering the market. Despite extensive research across Europe, seafood mislabeling in Croatia has remained unexplored. This study aims to provide the first comprehensive assessment of seafood labeling accuracy in Croatia, where fisheries are integral to the coastal economies and tourism. Using DNA barcoding of the COI gene, 109 seafood samples were collected over two years from various sources, including restaurants, markets, and fishing vessels, and analyzed for potential mislabeling. Results revealed a mislabeling rate of 3% among fish samples and 20% among cephalopods, with notable substitutions, such as the yellowfin tuna mislabeled as bigeye tuna and Bluefin tuna and the European squid mislabeled as Patagonian squid. Additionally, 38.5% of samples were partially labeled, while 32% lacked clear country-of-origin information, complicating traceability. While the findings align with the mislabeling rates in other European countries, this study underscores the ongoing challenges in seafood labeling compliance. Establishing standardized monitoring protocols will be essential for improving comparability and effectively addressing seafood fraud. Full article

Dry-cured tuna products exhibit unique aroma characteristics appreciated by local consumers, particularly in the southern Iberian Peninsula. In the present study, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC/MS) was used to identify and quantify volatile organic compounds (VOCs), establishing a volatile fingerprint of dry-cured tuna throughout the manufacturing process. Unsupervised (PCA) and supervised (PLS-DA and sPLS-DA) multivariate statistical methods were applied to visualise, group, and classify the samples. A total of fifty-four VOCs were identified across the four steps involved in processing the final product. The ML-PLS-DA model demonstrated excellent discrimination (R² = 0.912, Q² = 0.878, and Accuracy = 1) for the samples. Additionally, ML-sPLS-DA was conducted to screen various VOC metabolites in the samples after both the salting and salt-washing steps; the levels of eighteen VOCs changed significantly (VIP > 1; p < 0.05). These results provide a theoretical basis for determining flavour formation and quality control in the traditional dry-curing process of tuna. Full article

Bioactive peptides represent a promising therapeutic approach for Alzheimer’s disease (AD) by maintaining cholinergic system homeostasis through the inhibition of acetylcholinesterase (AChE) activity. This study focused on extracting AChE inhibitory peptides from yellowfin tuna pancreas using moderate ultrasound-assisted enzymatic hydrolysis (MUE). Firstly, papain and MUE stood out from five enzymes and four enzymatic hydrolysis methods, respectively, by comparing the degree of hydrolysis and AChE inhibitory activity of different pancreatic protein hydrolysates. Subsequently, the optimal MUE conditions were obtained by single-factor, Plackett–Burman, and response surface methodologies. The pancreatic protein hydrolysate prepared under optimal MUE conditions was then purified by ultrafiltration followed by RP-HPLC, from which a novel AChE inhibitory peptide (LLDF) was identified by LC-MS/MS and virtual screening. LLDF effectively inhibited AChE activity by a competitive inhibition mechanism, with an IC₅₀ of 18.44 ± 0.24 μM. Molecular docking and molecular dynamic simulation revealed that LLDF bound robustly to the active site of AChE via hydrogen bonds. These findings provided a theoretical basis for the valuable use of yellowfin tuna pancreas and introduced a new viewpoint on the potential therapeutic advantages of AChE inhibitory peptides for future AD treatment. Full article

Tuna are economically important as food resources in food markets. However, because tuna is often processed into steaks or fillets, the meat can be difficult to identify through morphological features. For effective fishery management and to protect the rights of consumers, it is necessary to develop a molecular method to accurately identify the species used in tuna products. Herein, we discovered five single-nucleotide polymorphism (SNP) sites via 2b-RAD sequencing and developed five SNP-based real-time polymerase chain reaction assays for the rapid identification of five highly priced tuna species. Three species-specific TaqMan systems were designed to identify albacore tuna (Thunnus alalunga), bigeye tuna (T. obesus), and southern bluefin tuna (T. maccoyii) and two cycling systems were designed to identify yellowfin tuna (T. albacares) and Atlantic bluefin tuna (T. thynnus). The systems showed good specificity and sensitivity (sensitivity of 0.0002 ng μL⁻¹ for albacore tuna, bigeye tuna, and southern bluefin tuna and 0.002 ng μL⁻¹ for yellowfin tuna and Atlantic bluefin tuna). Both systems were able to distinguish the target species from other species in a specific, sensitive, and accurate manner. Thus, these methods can be employed for the identification of species used in tuna products, protecting consumers and producers from economic fraud. Full article

The global tuna canning industry generates substantial volumes of by-products, comprising 50% to 70% of the total processed material. Traditionally, these by-products have been utilized in low-value products such as fish oils and fishmeal. However, there is significant potential to extract high-value compounds from these by-products, such as calcium phosphates (CaP), which can have pharmaceutical, agricultural and biotechnological applications. This work explores the potential of tuna canning by-products, particularly mineral-rich fractions (central skeleton, head and fish bones) as sources of calcium phosphates (CaP), offering a sustainable alternative to conventional synthetic derivatives within a circular bioeconomy framework. By-products from two of the most exploited species (yellowfin and skipjack) were subjected to enzymatic hydrolysis and chemical extraction, followed by controlled calcination to obtain CaP. The content of organic matter, nitrogen, total proteins, lipids and amino acids in the cleaned bones, as well as the main chemical bonds, structure and elemental composition (FT-Raman, XRD, XRF) were evaluated. Results indicated that the highest recovery yield of wet bones was achieved using the chemical method, particularly from the dorsal and caudal fins of yellowfin tuna. The proximal composition, with ash content ranging from 52% to 66% and protein content varying between 30% and 53%, highlights the potential of tuna skeleton substrates for plant growth formulations. Furthermore, variations in crystalline structures of the substrates revealed significant differences depending on the by-product source and species. XRD and Raman results confirmed a monophase calcium phosphate composition in most samples from both species, primarily based on hydroxyapatite (central skeleton, caudal and dorsal fin) or whitlockite/β-tricalcium phosphate (viscera), whereas the heads exhibited a biphasic composition. Comparing the species, yellowfin tuna (YF) exhibited a hydroxyapatite structure in the branchial arch and scales, while skipjack (SKJ) had a biphasic composition in these same regions. Full article

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. Full article

The presence of ammonia nitrogen in water has a significant impact on the serum and spleen of fish, potentially leading to changes in substances such as proteins in the serum while also causing damage to the immune function of the spleen. To investigate the effects of ammonia nitrogen (NH₃-N) stress on juvenile yellowfin tuna (Thunnus albacares), this study established three NH₃-N concentrations, 0, 5, and 10 mg/L, denoted as L0, L1, and L2, respectively. Serum and spleen samples were collected at 6, 24, and 36 h. The effects of different NH₃-N concentrations and exposure times on the physiological status of juvenile fish were investigated by analyzing serum biochemical indices and splenic gene expression. The results indicate that in the L1 group, the serum high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), complement 3 (C3) and complement 4 (C4) levels, and acid phosphatase (ACP) activity showed a trend of initially increasing and then decreasing. In the L2 group, the serum low-density lipoprotein cholesterol (LDL-C), HDL-C, and C4 levels and ACP activity also displayed an initially rising and then declining trend, while TG, C3, and creatinine (CRE) levels and alkaline phosphatase (AKP) activity showed an upward trend. In the L1 group, glutathione peroxidase 1b (GPX1b), interleukin 10 (IL-10), interleukin 6 receptor (IL-6r), and tumor necrosis factor alpha (TNF-α) gene expression levels in the spleen exhibited a trend of first increasing and then decreasing. In the L2 group, IL-10, IL-6r, tumor necrosis factor beta (TNF-β), caspase 2 (casp2), and caspase 9 (casp9) gene expression levels in the spleen also showed an initial increase followed by a decrease. When NH₃-N levels are below 5 mg/L, it is recommended to limit stress exposure to no more than 36 h for the juvenile fish. For concentrations ranging from 5 to 10 mg/L, stress should be strictly controlled to within 24 h. Exposure to high NH₃-N levels may affect biochemical indicators such as serum lipid metabolism, immunity, and metabolism in juvenile fish, and may damage the expression of antioxidant, immune gene, and apoptosis factors in the spleen. This study aims to deepen our understanding of the effects of NH₃-N on juvenile tuna, with the goal of establishing effective water quality monitoring and management strategies. This will ensure the quality of aquaculture water, reduce the harm caused by NH₃-N to juvenile yellowfin tuna, and enhance aquaculture efficiency and product quality. Full article

This study investigates the valorization potential of yellowfin tuna (Thunnus albacares) tails to produce high-value commercial products. Firstly, the tuna tails were placed in a perforated stainless-steel cylinder, and hydraulic pressure was applied to separate the skin from the muscle in the tails. The extracted muscle was then utilized as a nitrogen source for the growth of the proteolytic enzyme producer Bacillus subtilis, while the skins were employed for gelatin extraction. The proteases from B. subtilis were partially purified and used to produce antioxidant peptides from the obtained gelatin. The gelatin formed a gel upon cooling, with gelling and melting temperatures of 16 °C and 22 °C, respectively, and a Bloom strength of approximately 160. Response Surface Methodology (RSM) was employed to determine the optimal hydrolysis conditions to achieve the highest antioxidant activity (35.96% measured as DPPH radical scavenging activity), which were 50 °C and 6.5 IU of enzyme. The findings emphasize the importance of an integrated approach to maximize the value of tuna by-products, promoting sustainability within the framework of a circular bioeconomy. Overall, these results contribute to the efficient utilization of tuna by-products, waste reduction, and enhanced economic viability of the tuna industry. Full article

This study investigated the effects of acute ammonia nitrogen (NH₃-N) exposure on kidney antioxidant ability and phosphatases and related gene expression in juvenile yellowfin tuna (Thunnus albacares). The 180 juvenile yellowfin tuna (260.39 ± 55.99 g, 22.33 ± 2.28 cm) were exposed to ammonia for 6, 24, and 36 h using natural seawater (0 mg/L) as a control and NH₃-N at 5 and 10 mg/L. The lipid peroxidation byproduct malondialdehyde (MDA) and the levels of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-PX), alkaline phosphatase (AKP), and acid phosphatase (ACP), were measured using the colorimetric method in the trunk kidney to determine changes in antioxidant ability and phosphatase activity of juvenile yellowfin tuna exposed to NH₃-N. Results indicated that, at 36 h, MDA, SOD, CAT, and GSH-PX levels rose in the 5 mg/L group versus the control. In the 10 mg/L group, MDA and SOD, CAT, and GSH-PX activities significantly increased after 24 and 36 h exposure compared to the control. Phosphatases play a pivotal role in the immune system. AKP activity significantly increased at 6 h, and ACP activity markedly rose at 36 h in the 5 mg/L group versus the control. Real-time fluorescence quantitative PCR was applied to detect alterations in the antioxidant genes SOD2, CAT, and glutathione peroxidase 1b (GPX1b) and immune cytokines-related genes Interleukin 10 (IL-10) and Interleukin 6 receptor (IL-6r) expression in the head kidney in juvenile tuna. Relative to the control, antioxidant gene expression in the 5 mg/L group significantly rose at 6 and 36 h, and in the 10 mg/L group, SOD2 and GPX1b were significantly elevated at 36 h. Compared to the control group, IL-10 expression in the 5 mg/L group significantly increased at 6 h, whereas IL-6r expression decreased. In the 10 mg/L group, both IL-10 and IL-6r levels were observed to be lower. Low ammonia nitrogen concentrations boost antioxidant defenses, phosphatase activities, and gene expression levels, whereas higher levels may induce suppressive effects. In yellowfin tuna juvenile farming, NH₃-N concentration significantly affects the health of the juveniles. When the NH₃-N concentration is between 5–10 mg/L, the stress duration should be limited to 24 h; if the concentration is below 5 mg/L, the stress duration can be extended to 36 h. Full article