Search Results (164)

The placement of hydraulic elements in existing pool-type fishways to make them more suitable for Cyprinid fish is an issue of increasing interest in fishway research. Hydrodynamic characteristics and fish behavior at the representative pool of the fishway with bottom orifices and notches were assessed at the Dagdelen hydropower plant in the Ceyhan River Basin, Türkiye. Three-dimensional velocity measurements were taken in the pool of the fishway using an Acoustic Doppler velocimeter. The measurements were taken with and without a brush block at two different vertical distances from the bottom, which were below and above the level of bristles tips. A computational fluid dynamics (CFD) analysis was conducted for the studied fishway. The numerical model utilized Large Eddy Simulation (LES) combined with the Darcy–Forchheimer law, wherein brush blocks were represented as homogenous porous media. Our results revealed that the relative submergence of bristles in the brush block plays a very important role in velocity and Reynolds shear stress (RSS) distributions. After the placement of the submerged brush block, flow velocity and the lateral RSS component were reduced, and a resting area was created behind the brush block below the bristles’ tips. Fish movements in the pool were recorded by underwater cameras under real-time operation conditions. The heatmap analysis, which is a 2-dimensional fish spatial presence visualization technique for a specific time period, showed that Capoeta damascina avoided the areas with high turbulent fluctuations during the tests, and 61.5% of the fish presence intensity was found to be in the low Reynolds shear regions in the pool. This provides a clear case for the real-world ecological benefits of retrofitting existing pool-weir fishways with such flexible hydraulic elements. Full article

The effective assessment and improvement of water quality require analysis not only of the main river flowing into the sea but also of its tributaries, which may contribute to significant pollution. This study aimed to evaluate the physicochemical conditions of water in nine streams flowing into the Rega River between 2018 and 2022. It also sought to determine whether the water quality in these tributaries meets the standards defined by EU regulations for inland waters that serve as habitats for fish. The parameters analyzed included water temperature, dissolved oxygen (DO), pH, total suspended solids (TSSs), electrical conductivity (EC), alkalinity, total hardness (TH), biochemical oxygen demand (BOD₅), nitrite nitrogen (NO₂⁻-N), ammonium nitrogen (NH₄⁺-N), and total phosphorus (TP). The results indicated that most indicators met the requirements for waters suitable for salmonid species. Elevated concentrations of NO₂⁻-N observed across all sites were still within acceptable limits for cyprinid species. Among the parameters studied, TSSs was identified as the main factor that downgraded water quality over the study period. Principal component analysis (PCA) showed that the dominant variables influencing water chemistry were NH₄⁺-N, NO₂⁻-N, TP, EC, and chloride (Cl⁻), all of which are associated with anthropogenic sources. Full article

Invasive species often defy theoretical expectations, successfully establishing and spreading despite reduced propagule pressure and limited genetic diversity. What genomic mechanisms underpin this paradox? How do adaptive processes and host–pathogen interactions shape invasion outcomes? And which genes drive resistance and modulate pathogen virulence? Here, we address these questions using a model of co-invasion: the Asian topmouth gudgeon (Pseudorasbora parva) and its fungal parasite the Rosette agent (Sphaerothecum destruens), a system with profound ecological and economic consequences. Here by (1) mapping the reads obtained by Illumina sequencing on a previously deposited P. parva genome from Germany, (2) identifying SNPs and (3) creating a consensus sequence, we generated the first whole genome of an invasive P. parva population in France and compared it to a German population to explore patterns of genetic diversity, local adaptation, and potential signatures of pathogen resistance. Despite historical bottlenecks, our results reveal unexpectedly high levels of genomic diversity between these invasive populations. We identify candidate loci linked to immune function and provide insights into the evolutionary dynamics of co-introduction. These findings offer a rare window into how invasive species maintain adaptability and how pathogens may co-evolve during range expansion. Beyond advancing our understanding of invasion biology, the genomic resources generated here pave the way for translational approaches, including the development of genome-editing strategies aimed at mitigating the impact of invasive species and their associated pathogens. This work marks a critical step toward unraveling the complex interplay between genetics, ecology, and evolution in biological invasions. Full article

In this study, we sequenced and characterized the complete mitochondrial genome of Acorssocheilus spinifer, an endemic stream-dwelling cyprinid species from South China first described in 2006. The mitogenome is 16,591 bp in length and contains the standard set of 37 genes (13 protein-coding genes, 22 tRNA genes, 2 rRNA genes) plus a control region. The genome exhibits typical cyprinid characteristics, with most genes encoded on the H-strand and a nucleotide composition biased toward A + T (55.9%). All tRNA genes display the typical cloverleaf secondary structure, except for tRNA^Ser (GCU), which lacks the dihydrouridine (DHU) arm. Phylogenetic analysis using complete mitogenomes from 14 Acrossocheilus species revealed that 12 species form a monophyletic assemblage with three distinct clades. Within this framework, A. spinifer clusters closely with A. beijiangensis, supporting previous morphological observations. Our findings provide valuable genetic data for further taxonomic refinement and conservation efforts for Chinese barred species of Cyprinidae. Full article

Microecological preparations (MPs), encompassing probiotics, prebiotics, synbiotics, and postbiotics, are microbial feed supplements that enhance host health through gut microbiota modulation. Unlike the narrow definition of probiotics (viable microorganisms), MPs constitute a broader category including non-viable microbial derivatives and selectively fermented substrates. Their application in aquaculture significantly reduces antibiotic dependence. Given the industry’s intensification challenges, while meeting global protein demands, high-density aquaculture elevates disease risks, driving prophylactic antibiotic overuse. This practice accelerates antimicrobial resistance (AMR) development, compromising treatment efficacy and causing residual antibiotics in aquatic products. Such residues violate international food safety standards, triggering trade disputes. As sustainable alternatives, MPs operate through multiple mechanisms: the competitive exclusion of pathogens, immune stimulation, and nutrient absorption enhancement. This review examines the patterns of antibiotic abuse and the emergence of AMR in carp aquaculture, evaluates MP-based mitigation strategies from the perspective of antibiotic alternatives, and analyzes the advantages, disadvantages, and application progress of MPs. Based on existing evidence, we propose targeted research priorities for MP optimization, advocating for scientifically guided implementation in commercial cyprinid aquaculture. Full article

Cyvirus cyprinidallo3, also known as Cyprinid herpesvirus 3 (CyHV-3), is a common pathogen of koi and common carp (Cyprinus carpio). Infection of CyHV-3 can lead to high mortality in fry under 4 months of age. CyHV-3 can become latent in recovered fish, and latent CyHV-3 can reactivate under stress conditions and spread the virus. Reactivation of CyHV-3 can also lead to mortality and diseases in latently infected fish. No effective drugs are available to prevent CyHV-3 infection or reactivation from latency. There is a need for the discovery of anti-CyHV-3 drugs. Harmine (HAR) and harmaline (HAL) are β-carboline alkaloids found in the medicinal plant Peganum harmala with antiviral activities against many viruses, including HSV. Here, HAL was evaluated against CyHV-3 infection in vitro and in vivo, respectively. Immediately after a one-hour infection exposure of ~1000 FPU/plate or ~500 PFU/plate, cells treated with 5 µM HAL for 2 h can block nearly 50% or 90% plaque formation in vitro. Only around 50% inhibition was observed in cells treated with the common anti-herpesvirus drug acyclovir (ACV) at 10 or 20 µM for 2 h following 1 h post-infection of ~500 PFU/plate. Cells treated with 10 µM HAL for 30 min, 60 min, 2 h, and 6 h can reduce 60%, 65%, 85.5%, and 85% CyHV-3 replication in vitro, respectively. HAL at 20 µM is still effective against CyHV-3 DNA replication and virion production when the treatment started at 3 and 5 days post-infection for 1 or 2 h, respectively. HAL under 50 µM has little toxicity to cells treated for 24 h. Immersion treatment with 10 µM HAL for 3–4 h daily within the first 5 days post-infection can increase the survival of fry by 60%. In addition, IM injection of HAL at 20 µM can reduce the rate of CyHV-3 reactivation induced by heat stress in latently infected koi. This study demonstrated that HAL could potentially be used to prevent CyHV-3 infection or reactivation from latency. Full article

Cyvirus cyprinidallo2 (CyHV-2) is the causative agent of herpesviral hematopoietic necrosis in several economically important farmed freshwater fish species of the genus Carassius. Despite several CyHV-2 strains being isolated and fully sequenced, there is a lack of detailed characterization and consistent information on strains that exhibit high virulence in adult goldfish through viral challenge by immersion, particularly in the context of European strains and host populations. Strains that can cause highly virulent disease via this inoculation route are much more compatible with experimental designs that are representative of natural infection; thus, their utilization provides greater biological relevance. Consequently, in this study, we isolated three novel strains of CyHV-2 (designated NL-1, NL-2, and NL-3), originating from outbreaks in The Netherlands. Full-length genome sequencing and phylogenetic analyses revealed that these newly isolated strains are distinct from known strains and from each other. Significant differences were observed between the strains, in terms of in vitro growth kinetics, with NL-2 exhibiting stable passaging and superior fitness in vitro. Importantly, the challenge of adult Shubunkin goldfish with the NL-2 strain via immersion (2000 PFU/mL) induced an average mortality of ~40%, while parallel experiments with the CyHV-2 reference strain ST-J1 resulted in no mortality. Taken together, this study represents the characterization of a new CyHV-2 in vivo infection model, much more compatible with experimental designs that are required to be representative of natural infection. This model will be extremely useful in many aspects of CyHV-2 research in the future. Importantly, the genetic and phenotypic characterization performed in this study generates hypotheses on the potential roles of CyHV-2 genes in adaptation of the virus in vitro or in vivo. Full article

Cold-water lakes in high-latitude regions are experiencing rapid changes in community structure and functioning associated with local and global stressors (e.g., climate change, hydropower and invasive species). However, the long-term ecological responses of cold-adapted top predators are relatively poorly monitored despite their high importance for structuring ecological communities and for the provisioning of ecosystem services. We studied long-term changes (2010–2021) in the population structure and trophic niche of two cold-adapted coregonid fishes in oligotrophic Lake Osensjøen, southeastern Norway. Our gillnet surveys indicated that the whitefish (Coregonus lavaretus) population declines simultaneously with the increasing population density of roach (Rutilus rutilus), whereas vendace (Coregonus albula) showed more stable densities. Both whitefish and vendace became increasingly dominated by small-sized individuals following the increase in coexisting roach and perch (Perca fluviatilis) populations. Our stomach content and stable isotope data indicated a marked overlap in the trophic niches of whitefish and roach, with both species showing high among-individual variation in δ¹³C and δ¹⁵N values as compared to the more specialized zooplanktivorous vendace. Our study provides further evidence that the ongoing environmental changes in high-latitude lakes may induce rapid changes in community structures and lead to the population declines of cold-adapted fishes, likely associated with strong resource competition with warm-adapted cyprinid and percid fishes. Such shifts in fish community structure may, in turn, affect the benthic and pelagic food-web compartments and reduce valuable ecosystem services such as local fisheries targeting salmonids. Full article

Discogobio is a genus of small, economically important freshwater fishes that are widely distributed in Southwestern China. The species of the genus are morphologically very similar, which makes their taxonomic identification quite challenging. DNA barcoding technology can identify species at the molecular level, thus overcoming the limitations of morphological classification. In this study, we collected 16 morphological species of Discogobio from China, analyzed the mitochondrial cytochrome oxidase I subunit (COI) gene sequences of 206 samples, and applied DNA barcoding to identify the species. The COI amplicon was 651 bp in length, and the mean base contents were: (T) 28.83%, (C) 27.63%, (A) 25.97%, (G) 17.57%. The AT content (54.8%) was higher, and the base composition was biased. The intraspecific differences in the genus Discogobio were not significant, and the genetic distances were all less than 2%. The average interspecific genetic distances (3.94%) were about 18.8 times the average intraspecific genetic distances (0.21%), suggesting that there are barcode gaps among the species of the genus Discogobio. Five different species definition methods, Automatic Barcode Gap Discovery (ABGD), Assemble Species by Automatic Partitioning (ASAP), Bayesian Poisson Tree Process (bPTP), Generalized Mixed Yule Combination (GMYC), and Refined Single Linkage (RESL), were used to infer molecular operational taxonomic units (MOTU). The number of MOTUs ranged from 9 to 18. Phylogenetic analysis based on COI gene haplotypes showed that most species formed well-evolved branches on the phylogenetic tree, and the clustering among species was obvious without mixing. The results of this study provide reliable DNA barcoding information for species identification within the genus Discogobio, which is of great significance for taxonomic identification. Full article

This study investigates the prevalence of parasitic helminths in free-ranging domestic cats and dogs near the Chi River and natural reservoirs in Maha Sarakham Province, Thailand. Fecal samples from 39 cats and 148 dogs were analyzed using a modified formalin-ether concentration technique (FECT). The overall prevalence of helminth infections was 64.1% in cats and 51.4% in dogs. Common parasites were detected including soil-transmitted species like Ancylostoma sp. (hookworm), Toxocara spp., and Strongyloides sp., as well as foodborne helminths such as Taenia sp., Hymenolepis sp., Spirometra sp., and Opisthorchis sp. Multiple parasitic infections were commonly found in dogs (57.9%) and cats (46.2%). Our findings suggest that domestic cats and dogs act as important reservoirs for zoonotic helminths in the region. Notably, Opisthorchis viverrini-like eggs were found exclusively in cats, with a prevalence of 23.1%. The intron 5 of domain 1 of the taurocyamine kinase gene (TkD1Int5) was used for genotyping O. viverrini-like eggs. All O. viverrini-like egg samples with TkD1Int5 haplotypes (Ov116–Ov123) were uniquely found in cats. Genetic analysis revealed that TkD1Int5 haplotypes were similar to those previously reported for Opisthorchis viverrini in various species of cyprinid fish across opisthorchiasis-endemic regions in Thailand and Lao PDR. Three TkD1Int5 haplogroups (I–III) were classified, with O. viverrini-like eggs from cats distributed across all haplogroups. Notably, one haplotype (Ov118) was genetically distinct from the others and did not cluster into any haplogroup. These findings highlight the crucial role of cats as reservoir hosts and their potential contribution to the transmission of the zoonotic liver fluke O. viverrini, posing a notable public health concern. Full article

Acrossocheilus Oshima, 1919, a cyprinid genus of Cyprinidae in southern China and currently comprises 26 valid species. In this study, we describe Acrossocheilus dabieensis sp. nov. from the Dabie Mountains, China. This new species differs from its congeners by the following combination of characters: The second primary vertical bar (PB2) is situated beneath the anterior origin of the dorsal fin in females and subadult males. Vertical bars extend to the end of the ventral abdomen in juveniles, and they gradually recede above the lateral line in adult females, whereas they are absent in adult males. The last unbranched dorsal-fin ray is slender with a smooth posterior margin. Phylogenetic analyses based on the mitochondrial DNA sequences indicate that A. dabieensis sp. nov. is a monophyletic group, and it forms a sister group with A. kreyenbergii, reinforcing the status of the new species. A key to the barred species of Acrossocheilus is also provided. Full article

Cyprinid herpesvirus 2 (CyHV-2) is a major pathogen posing a serious threat to crucian carp farming and has led to major economic losses in China’s aquaculture industry. This research aimed to explore how the CyHV-2-ORF41 protein influences viral replication. Firstly, we found that ORF41 overexpression in Gibel carp brain (GiCB) cells significantly enhanced CyHV-2 replication. Subsequently, GST pull-down and LC-MS/MS analyses were conducted to identify ORF41’s protein interactions. The results showed that ORF41 might interact with pyruvate dehydrogenase (PDH)-E1β, an enzyme connecting glycolysis to the tricarboxylic acid (TCA) cycle. Furthermore, ORF41 expression decreased the PDH-E1β levels, leading to pyruvate and lactic acid accumulation. Molecular docking and dynamics simulations confirmed a stable interaction between ORF41 and PDH-E1β. This research not only deepens our understanding of CyHV-2’s mechanisms of infection but also suggests potential targets for therapeutic strategies in aquaculture. Full article

Spring viremia of carp virus (SVCV) is a significant pathogen that has notably hindered the advancement of cyprinid aquaculture in recent years. Infections caused by SVCV are often associated with substantial economic losses due to the absence of effective treatment options. Previous reports indicated that N-(4-methyl-2-oxo-2H-chromen-7-yl) benzenesulfonamide (N6) exhibits inhibitory effects on SVCV proliferation. This study aims to comprehensively evaluate the anti-SVCV effects of N6 using healthy young carp as the experimental model. The research investigates the antiviral activity of this compound in vivo, the immune response of interferon (IFN)-related genes, its impact on the horizontal transmission of SVCV, and histopathological changes. The results indicate that N6 significantly inhibits SVCV infectivity and apoptosis in EPC cells in vitro. Furthermore, while N6 reduced horizontal transmission of SVCV in a static cohabitation challenge model, the N6-treated SVCV-infected group showed a nearly 3-fold decrease in viral load compared to the control group, it did not completely prevent transmission at established antiviral dosages. Histopathological analysis of the affected fish revealed that N6 effectively mitigated tissue damage induced by SVCV. Additionally, the up-regulation of six IFN-related genes suggests that N6 may indirectly activate IFNs to facilitate the clearance of SVCV in the kidney and spleen, as demonstrated by quantitative reverse transcription polymerase chain reaction (qRT-PCR). These findings provide a foundation for further investigations into the mechanisms by which N6 acts against SVCV and may aid in the development of novel anti-SVCV therapeutics. Full article

Onychostoma macrolepis is not only a protected Cyprinid species in the wild but also an emerging commercial aquaculture fish in China. The objective of this research was to genetically modify the genes associated with commercial traits by CRISPR/Cas9 for the protection and utilization of the germplasm resources of O. macrolepis. To that end, one-cell stage embryos were obtained via hormone-induced ovulation and artificial insemination in O. macrolepis. Eight genes related to body color, growth, intermuscular bone, and sex differentiation were mutated in O. macrolepis using the CRISPR/Cas9 system by microinjection of gRNA/Cas9 mRNA. The optimal dose of gRNA/Cas9 mRNA was determined by injection of different concentrations of tyr (tyrosinase)-gRNA/Cas9 and examination of the mutation rate and hatching rate of embryos. Indels were detected by T7 endonuclease I digestion and Sanger sequencing. F0 mutants with high mutation rates were selected for phenotype analyses. Disruption of body color gene tyr, mpv17 (mitochondrial inner membrane protein MPV17), and csf1ra (colony-stimulating factor 1 receptor, a) resulted in obvious phenotype with decreased or even absence of melanophores, iridophores, and xanthophores, respectively. Mutation of mstnb (myostatin b) led to improved growth performance. Mutation of mc4r (melanocortin 4 receptor) led to no obvious phenotype. Mutation of runx2b (RUNX family transcription factor 2b) and bmp6 (bone morphogenetic protein 6) resulted in decreased or absence of intermuscular bones, as revealed by alizarin red S staining. Mutation of cyp19a1a (cytochrome P450, family 19, subfamily A, polypeptide 1a) resulted in ovarian degeneration as revealed by gonadal histological examination. Therefore, this study successfully obtained mutants with obvious phenotypes of genes associated with body color, growth, intermuscular bone, and sex differentiation by CRISPR/Cas9 in O. macrolepis. Full article

The Catalan chub, Squalius laietanus, was described in 2007 and has recently reached Vulnerable status on the IUCN Red List of Threatened Species. The assigned range for this species includes the lower course of the Ebro River in Spain and northwards to the Tech, Têt, Agly, and Massane Rivers in Southeastern France. In this study, 246 chub specimens caught at 15 sites in the nine main river basins of the Spanish range were barcoded by sequencing a 624 bp fragment of the mitochondrial COI gene. Squalius laietanus haplotypes were found in 68% of the fish caught. In a tributary of the Ebro River, all specimens (6%) were identified as the Tagus chub, S. pyrenaicus, another endemic Iberian chub species. The remaining fish (26%) had a haplotype typical of the European chub, S. cephalus, populations outside Spain. This haplotype was present in six sites in four basins, being particularly abundant in the Ebro River. Considering that Squalius species can hybridize with other native and non-native cyprinid species, the potential co-occurrence of several species in the same site or basin raises concerns about the real extent of an exclusive range for the Catalan chub and the integrity of its native gene pools throughout its range. Full article