Search Results (201)

The northern pike (Esox lucius) is an economically important cold-water fish species in northern China. It exhibits pronounced sexual dimorphism, yet the molecular mechanism underlying its sex differentiation remains unclear, which hinders the development of aquaculture. Whole-transcriptome sequencing is a powerful approach for screening sex-related genes; however, no such study has been reported for this species to date. In this study, gonadal tissues from three female and three male E. lucius were collected for whole-transcriptome sequencing. A total of 14,941 differentially expressed messengerRNAs, 119 differentially expressed microRNAs, 229 differentially expressed circularRNAs, and 2055 differentially expressed long non-codingRNAs were identified. Functional enrichment analysis revealed that the differentially expressed genes were significantly enriched in pathways closely associated with sex differentiation, such as steroid hormone biosynthesis and oocyte meiosis. Several key sex-biased genes were identified, including female-biased genes (FANCL, DDX5, SRSF5B) and male-biased genes (STAR, FDX1B, ITGA2B). Furthermore, a competing endogenous RNA (ceRNA) regulatory network involving dre-miR-107b was constructed, which may represent a candidate for further investigation into sex differentiation in E. lucius. This study provides the first comprehensive whole-transcriptome dataset of female and male gonads in E. lucius, identifies key sex-biased genes and core pathways involved in its sex differentiation, and thereby identifies the dre-miR-107b-centered ceRNA network and key sex-biased genes (FANCL, DDX5, SRSF5B, STAR, FDX1B, ITGA2B) as core molecular players in sex differentiation of this species. Full article

Extreme high-temperature events driven by global climate change are occurring with increasing frequency, posing a serious threat to the stability of aquatic ecosystems. The Tibetan schizothoracin (Gymnocypris eckloni), a cold-water fish species endemic to the Qinghai–Tibet Plateau, is highly sensitive to temperature fluctuations and serves as an ideal model for studying the effects of climate change on fish. As a key organ for fish to perceive environmental changes, the gills’ comprehensive response mechanism has not yet been fully elucidated. This study investigated the effects of acute heat stress on the gill tissue of G. eckloni. The results showed that acute heat stress caused severe histopathological damage in the gills, including lamellar curling, epithelial cell detachment, and edema, with a significant increase in apoptosis. Biochemical analysis revealed elevated levels of cortisol, glucose, and ATPase activity in serum, as well as increased MDA content and CAT activity in the gills. Transcriptomic analysis identified 2304 DEGs. Upregulated DEGs were significantly enriched in pathways related to inflammatory response, TNF signaling, ferroptosis, and apoptosis, while downregulated DEGs were primarily involved in peroxisome metabolism, cell cycle, and steroid biosynthesis. This study confirms that acute heat stress induces structural damage and functional impairment in the gills by activating inflammatory and apoptotic pathways and disrupting redox homeostasis. It elucidates the immediate molecular and physiological responses of G. eckloni gills to acute heat stress. Follow-up experiments will be conducted at multiple time points, across different temperature gradients, and under chronic stress conditions to gain a more comprehensive understanding of the adaptive potential of high-altitude fish to climate warming, thereby providing a scientific basis for the development of conservation strategies. Full article

In many industrial applications, the significant differences in flow rates and physical properties between the hot and cold media of plate heat exchangers (PHEs) often lead to differentiated performance requirements. Asymmetric structural design is an effective approach to addressing these specific needs. In this paper, a novel fish-scale corrugated asymmetric plate heat exchanger (APHE) was designed and multi-objective optimization was performed based on the objectives of minimizing the water side pressure drop, ΔP, and maximizing the overall heat transfer coefficient, K. Numerical simulations of the fish-scale corrugated APHE were conducted with the Box–Behnken Design (BBD) in the Response Surface Methodology (RSM). The corrugation angle, corrugation pitch, and protrusion ratio were selected as geometric variables. Through Analysis of Variance (ANOVA), significant regression models were established for the two competing performance indicators. Subsequently, Pareto optimal solutions were identified using the fast and elitist non-dominated sorting genetic algorithm (NSGA-II). A comparison of the performances reveals that the novel APHE reduces ΔP by 47.13% and increases K by 5.77% compared to the original chevron-type PHE. Further analysis of the simulation data reveals that the convective heat transfer coefficient on the refrigerant side is increased by 24.06%. These findings substantiate the benefits of the asymmetric feature of the fish-scale protrusion and offer a comprehensive and effective design strategy for APHEs. Full article

Background: Phoxinus grumi, a small leuciscid fish endemic to the Turpan Basin in Xinjiang, China, has long been the subject of taxonomic disputes, hindering accurate species identification and the understanding of its evolutionary history. Methods: To resolve this uncertainty, we sequenced and characterized the complete mitochondrial genome of P. grumi using next-generation sequencing. Results: The circular mitogenome is 16,604 bp long and comprises the typical 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and one control region, exhibiting gene overlap and intergenic spacing. The overall base composition shows a pronounced AT bias. Notably, all tRNA genes except tRNA-Ser1 fold into a typical cloverleaf secondary structure; tRNA-Ser1 lacks the dihydrouracil (DHU) arm, representing an unusual structural variation. All 13 PCGs have been subject to purifying selection (Ka/Ks < 1), with ATP8 evolving fastest and COX1 being the most conserved. Maximum likelihood (ML) and Bayesian inference (BI) phylogenetic analyses were conducted based on the concatenated sequences of the 13 mitochondrial PCGs, as well as the Cytb gene. Both datasets consistently placed P. grumi within the subfamily Pseudaspininae, forming a strongly supported sister relationship with the genus Rhynchocypris. This inference was further supported by Kimura two-parameter (K2P) genetic distance analyses, which revealed the smallest divergence between P. grumi and Rhynchocypris species (0.1620–0.1703), markedly smaller than that observed between P. grumi and core Phoxinus species (0.2475–0.2558). Conclusions: Together, these results support the placement of P. grumi within the East Asian Pseudaspininae lineage and help clarify its taxonomic position, which has long been debated. The complete mitochondrial genome of P. grumi provides additional mitogenomic data for phylogenetic analyses of Leuciscidae and contributes to a better understanding of the evolutionary relationships and diversification of Far Eastern leuciscids. These findings may also provide a molecular basis for future studies on the conservation genetics and environmental adaptation of this endemic cold-water fish from the arid Turpan Basin in northwestern China. Full article

Aquaculture in ponds supplied by streams or rivers requires careful evaluation of key physicochemical parameters and potential pollution threats, particularly metals and microplastics. To address these challenges, this research aims to monitor daily climatic and physicochemical parameters and quantify potentially toxic metals and microplastics in the water of 19 fishponds in the SCDP Nucet, Romania, over one winter season (i.e., December 2024 to February 2025). During this season, unique hydrochemical conditions arise, such as lower temperatures, reduced light, and decreased activity, which can affect the ecological balance and fish health. Accordingly, a total of 4650 samples were collected and analyzed in terms of physicochemical parameters (i.e., alkalinity, bicarbonate, calcium ions, magnesium ions, Ca²⁺/Mg²⁺ ratio, organic matter, nitrates, nitrites, phosphates, ammonium, total hardness, resistivity, dissolved oxygen, conductivity, salinity, turbidity, free and total chlorine), metals, and microplastics. Statistical analysis revealed the influence of winter weather on water quality, highlighting links between air and water temperatures and physicochemical parameters. Furthermore, water analyses revealed notable levels of microplastics, including fibers and fragments of various colors, shapes, and sizes. Polypropylene, polyethene, and nylon were the most prevalent. While appreciable quantities of blue, green, black, and yellow fibers were found in size ranges (0.09–0.3 mm), irregular yellow fragments or translucent particles were found in sizes less than 0.5 mm. Metal (i.e., Cr, Fe, Ni, Co, Cu, Zn, Cd, and Pb) concentrations do not exceed the standard values set by national and European regulations. However, it is worth noting that microplastics can amplify or mitigate metal toxicity. The results emphasize the importance of integrated monitoring of physicochemical parameters and emerging pollutants during the cold season, thereby improving understanding of the chemical processes governing water quality in fishponds, providing scientific support for future environmental risk assessment, and promoting innovative, adaptive technologies. Full article

Bats are reservoirs for many emerging viruses, yet broad-scale spatial patterns of bat viromes and their ecological determinants remain unclear, limiting spillover risk assessment. To address this, we conducted a standardized survey across central to southern China. During 2022–2023, fecal samples were collected from 527 bats representing 17 species at 21 caves in seven provinces. Using each cave as the analytical unit, samples from all species at a site were pooled to construct 21 fecal RNA virome libraries for metatranscriptomic sequencing; viral-like contigs were annotated, and viral alpha/beta diversity was quantified at the genus level. Sites were grouped by geographic distance and latitude to evaluate spatial differentiation and to relate virome patterns to host community attributes and environmental factors. We annotated 56 viral families, including 19 vertebrate-associated families, with multiple families and genera shared across geographic groupings. Vertebrate-associated viral diversity showed limited evidence of geographic isolation within the study region but suggested gradual turnover with latitude. Host species richness was the strongest correlate of virome diversity, exceeding the effects of evaluated environmental variables (e.g., climate and human activity). These results support prioritization of species-rich bat habitats for surveillance and risk assessment. Full article

The large yellow croaker (Larimichthys crocea) is a high-value marine fish, but stress during live transport often leads to physiological disturbance and deterioration of muscle quality. This study investigated the effects of pre-transport temporary rearing at three temperatures (8, 10, and 12 °C) over 48 h on stress response, energy allocation, and muscle quality in this fish species. Temporary rearing at 8 °C induced stronger cold stress, characterised by elevated cortisol, marked lipid mobilisation, late lactate rebound, and greater loss of polyunsaturated fatty acids, indicating enhanced stress–catabolism coupling and higher risk of quality deterioration. In contrast, 12 °C did not sufficiently suppress metabolic turnover, resulting in continuous glycogen depletion, rapid ATP degradation, and accelerated accumulation of bitter-tasting nucleotide metabolites such as hypoxanthine. Among the tested temperatures, 10 °C showed the most coordinated response, with relatively stable endocrine status, moderate substrate utilisation, lower accumulation of undesirable degradation products, and better preservation of texture, water-holding capacity, and flavour-related precursors. These findings suggest that 10 °C is a promising pre-transport temporary rearing temperature for large yellow croakers under the present 48 h experimental conditions. The advantage of this temperature appears to lie in achieving a more favourable balance between metabolic suppression and physiological homeostasis, thereby providing a scientific basis for improving pre-transport rearing management and supporting safer, more stable live transport. Future studies incorporating behavioural and molecular indicators are needed to further clarify the regulatory effects of 10 °C during pre-transport rearing. Full article

Understanding salmonid spawning dynamics is critical for conserving cold-water river ecosystems amid increasing human and climate pressures. This study developed and validated a species-specific eDNA (Salmo cf. trutta and Thymallus thymallus) and evaluated its performance for seasonal spawning activity monitoring using droplet digital PCR (ddPCR). Species-specific primers and probes targeting mitochondrial nd5 (S. trutta) and cytb (T. thymallus) genes were designed and optimized as a duplex assay. Performance assessments included in vitro validation, cross-amplification testing, and determining the LOB, LOD, and LOQ. Field validation over a year at two spawning sites in the Gradac River, Serbia, involved seasonal eDNA sampling, filtration, extraction, and ddPCR analysis. Fish community composition was also assessed with electrofishing and metabarcoding. The assay showed high specificity and sensitivity, with LODs of 0.14 cp/µL and LOQs of 0.99 and 1.25 cpµL for S. trutta and T. thymallus. S. trutta eDNA peaked in late autumn during spawning, while T. thymallus remained at or below detection limits, reflecting its lower abundance and different spawning season. Filter type affected filtration efficiency but not eDNA yield. These findings confirm ddPCR-based eDNA as a powerful, non-invasive tool for monitoring salmonid spawning and seasonal changes, supporting adaptive fisheries management and conservation amid environmental changes. Full article

Hybridization is pivotal for germplasm innovation, yet how reciprocal crossing regulates digestive characteristics in sub-cold-water fish remains unclear. This study systematically compared differences in intestinal morphology, physiological function, and microbial community assembly among herbivorous Schizothorax prenanti, carnivorous S. davidi, and their reciprocal hybrids using histological analysis, digestive enzyme assays, and 16S rRNA sequencing. Results indicated that parental intestinal characteristics were highly consistent with their feeding habits. Orthogonal hybrids exhibited a mosaic phenotype, combining the maternal muscular gut structure with high paternal-like lipase activity, and were characterized by an enrichment of the potential probiotic Lactococcus. In contrast, reciprocal hybrids presented a mismatch between morphology and function: despite developed hindgut folds, key digestive enzyme activities were low, and the gut microbiota was dominated by environmental bacteria such as Methylobacterium. Our findings indicate a spatially dependent assembly dynamic: the host genetic background strongly drives microbiome divergence in the anterior segments (foregut and midgut), whereas the long-term administration of a standardized diet ultimately promotes structural convergence in the hindgut. The orthogonal cross yielded a phenotype characterized by an apparent co-occurrence of specific host enzymes and distinct microbiota, suggesting an inferred physiological potential for lipid digestion that requires further multi-omics validation. These findings provide preliminary insights into the associations between genetic background and intestinal traits, providing a theoretical basis for the targeted breeding of Schizothorax species. Full article

Schizothorax wangchiachii, as a cold-water fish, is a predominant or common species in high-altitude areas with large population sizes. It is among the main edible economic fish species in the production area. We used genotype sequencing (GBS) technology to analyze the genetic diversity and population structure of 10 wild populations in the Jinsha River and Yalong River basins of the upper Yangtze River. A total of 724,858 single-nucleotide polymorphisms (SNPs) were detected in these 10 wild populations. The population genetic diversity was low; however, the degree of genetic differentiation was not significant. The populations from the Jinsha River and Yalong River could not be clustered separately on the basis of the SNPs. The Panzhihua (PZH) and Wudongde (WDD) populations from the Jinsha River exhibited gene flow with the Yajiang (YJ) population from the Yalong River, and a secondary pulse of gene flow subsequently connected the PZH and WDD populations to the upper-Jinsha population Suwalong (SWL). The demographic history of S. wangchiachii, reflected in its effective population size (N_e), has been influenced by the uplift of the Qinghai–Tibet Plateau (QTP). Furthermore, the identified SNPs are functionally associated with key cellular processes, environmental adaptation, and metabolism. These findings provide critical genomic insights that can inform conservation strategies and support the sustainable utilization of wild S. wangchiachii resources. Full article

Turbot (Scophthalmus maximus) is an economically vital cold-water fish frequently challenged by summer heat and low salinity. However, the temporal response of physiological circadian rhythms to such long-term stress remains underexplored. This study investigated antioxidant, immune, and endocrine rhythms in turbot acclimated to control (16 °C, 30 ppt), high-temperature (23 °C), and low-salinity (10 ppt) conditions for 30 days. Subsequently, time-series sampling was performed every 4 h for 72 consecutive hours. Under optimal conditions, hepatic superoxide dismutase (SOD), serum alanine aminotransferase (ALT), and melatonin exhibited robust 24 h rhythms. Long-term stress disrupted this homeostasis through divergent mechanisms. Low-salinity stress induced “rhythmic remodeling,” maintaining balance via phase shifts or novel infradian (48–72 h) oscillations in thyroid hormones (T3, T4) and ALT, without oxidative damage. Conversely, high-temperature stress triggered “rhythmic collapse,” characterized by a loss of daily rhythms in SOD and ALT, sustained inflammation indicated by elevated acid phosphatase (ACP), metabolic depression (suppressed T3), and malondialdehyde accumulation. These findings demonstrate that heat stress poses a more destructive threat to circadian integrity than hyposmotic stress. Consequently, the rhythmic dynamics of ACP, ALT, T3, and T4 are identified as critical indicators of stress status, serving as potential biomarkers for screening stress-tolerant strains for selective breeding. Full article

Spent coffee grounds (SCGs) represent a globally abundant agro-industrial byproduct with underexploited potential in circular bioeconomy applications. This study investigates the extraction, characterization and functional integration of SCG protein concentrate into aquafeed formulations for common carp (Cyprinus carpio). Protein was recovered through alkaline extraction followed by isoelectric precipitation, yielding a concentrate incorporated at 5% into a mixed plant and fishmeal diet produced by cold pelletizing. Compositional analysis performed by FT-NIR showed 33.6% crude protein, 7.24% lipids and 7.85% fiber, while ICP-OES confirmed substantial levels of essential minerals including Ca, P, K and Mg (15.3, 8.4, 10.4 and 2.3 g/kg). SCGs contributed bioactive compounds, with total polyphenols reaching 1.521 ± 0.065 mg GAE/g DM and an antioxidant capacity of 3.35 ± 0.03 mg TE/g DM. Pellets exhibited high water stability (91.8% retention after 30 min), and a short-term feeding test demonstrated strong acceptance by juvenile carp (91.2 ± 2.1%) consumption. Residual caffeine levels remained low (3.5 mg per g dry weight) and within safe exposure margins for freshwater fish. The results demonstrate the technical feasibility of incorporating SCG protein concentrate into compound aquafeeds without compromising pellet integrity or short-term palatability, while increasing feed-level antioxidant potential. However, the findings represent a proof-of-concept evaluation. Further research involving longer-term feeding trials, digestibility assessment, and amino acid profiling of complete diets is required to validate nutritional performance and optimize inclusion strategies for sustainable aquaculture. Full article

This study addresses a long-term failure to achieve the good ecological status for fish fauna required by the European Water Framework Directive (WFD) in the salmonid–rhithral zone in Bavaria, Germany. To identify the causes, we compared extensive fish population data from the Eger River with data from its twin river, the Röslau. The proportion of autochthonous cold, oligo-stenothermic fish species is significantly lower in the Eger (4.97% vs. 37.31%). In addition, continuous water temperature measurements were taken at five locations from spring to early autumn in 2023. The Eger showed significantly higher water temperatures throughout the measurement period. In midsummer, differences in daily maximum temperatures exceeded 10 °C at the same altitude. The proportion of cold-water fish in the population appeared to be negatively related to the mean of summer water temperature peaks (MWTP) (R = 0.95, p < 0.01). Accordingly, restoration measures in the Eger would need to reduce the MWTP from the current 19.1–20.5 °C to at least 16–16.5 °C, which requires more detailed data on the thermal footprint of individual hydraulic structures. The anthropogenic thermal impact on the Eger was overlooked as the root cause of the problem for many years, which largely explains the ineffectiveness of previous restoration measures. At least within the salmonid–rhithral zone, we consider the ability of the standardized fish-based assessment tool (fiBS) to detect thermal deterioration to be sufficient, provided it is applied with due care. Full article

Pineapple processing generates substantial waste, which has the potential to be valorized according to circular economy principles. This study aimed to estimate the amount of waste generation from the pineapple industry and demonstrate its valorization by producing pectin-based hydrogels for fat replacement in reduced-fat sausages, in addition to cellulose-derived edible films for sausage casings. An analysis of the pineapple sector in Thailand, covering 2015–2024, revealed an average annual pineapple waste generation of 670,698 tons. The crude fiber content in pineapple waste was found to be 15–33%. In this study, pectin was successfully extracted using citric acid under microwave digestion for 10 min. Through the combination of extracted and commercial pectins, a hydrogel (fat replacer) could be formed following the incorporation of calcium residue in fish bone powder. Substituting this hydrogel for 25% fat in sausage recipes reduced fat content while improving textural properties and water-holding capacities. The reduced-fat sausage, wrapped with edible film made from gelatin and carboxymethyl cellulose (CMC) derived from pineapple waste, exhibited physicochemical stability, as evidenced by its unchanged color and pH during cold storage for 5 days. Storing this type of sausage within films containing CMC from pineapple waste exhibited superior antioxidative properties compared to those wrapped with commercial films. Our results indicated that polysaccharide residues in pineapple waste can be valorized to produce reduced-fat sausages and casings, supporting upcycling policies and waste management strategies. Full article

This study aimed to assess various social–ecological traps of hilsa shad (Tenualosa ilisha) fisheries and to investigate the factors that significantly impact livelihood adaptation strategies during the ban period, based on fieldwork in coastal fishing communities. To collect empirical data, a total of 247 in-depth interviews were conducted using a semi-structured questionnaire along with six focus group discussions, oral history, and ten key informant interviews in the Chattogram and Patuakhali districts of Bangladesh. A conceptual framework derived from a strategy for reducing poverty, known as the Sustainable Livelihood Approach (SLA), is applied to determine the livelihood outcomes of hilsa fishers. The results showed that low income (<5000 BDT/month), high interest in loans from dadondar (lender) (10–12%) and aratdar (lessor of the vessel) (5%), high harvesting costs, an increasing number of hilsa fishermen, and intergenerational traps (81.78%) are creating social–ecological traps (SETs) in the hilsa fishery. The significant factors affecting the choice of adaptation strategies include family members, training facilities, home ownership, and belonging to a formal society. Apart from fighting against some extreme climate events, negative feedback comes from the absence of cold storage facilities, illegal use of fishing nets, frequent ban seasons, ignorance of conservation laws, limited opportunities for alternative occupations, and poor supply of drinking water. Hilsa fishermen in these regions depended on aratdar and dadondar for their financial support, which resulted in lower prices than the prevailing market prices. To escape from the SETs, this study identifies potential alternatives, such as government–community finance schemes, the promotion of alternative livelihoods, opportunities for technical education of their children, improvement of the local framework, and strong cooperation between local stakeholders and management authorities that are necessary to maintain the sustainability of hilsa fisheries. Full article