Fish Species Research Articles

Identification and functional characterization of interleukin-22 (IL-22) in orange-spotted grouper (Epinephelus coioides)

In mammals, IL-22 is considered as a critical cytokine regulating of immunity and homeostasis at barrier surfaces. Although IL-22 have been functional characterization in different species of fish, the studies about distinct responses of IL-22 in different organs/tissues/cell types is rather limited. Here, we identified and cloned IL-22 gene (named as Ec-IL-22) from grouper (Epinephelus coioides). Ec-IL-22 gene was detected in all orangs/tissues examined, and was induced in intestine, gill, spleen, head kidney, and primary head kidney/intestine leukocytes following the stimulation of LPS and poly(I:C), as well as Vibrio harveyi and Singapore grouper iridovirus infection (SGIV). In addition, the stimulation of DSS could induce the expression of Ec-IL-22 in intestine and primary leukocytes from intestine. Importantly, the treatment of recombinant Ec-IL-22 induced the mRNA level of proinflammatory cytokines in primary intestine/head kidney leukocytes. The present results improve the understanding of expression patterns and functional characteristics of fish IL-22 in different organs/tissues/cell types.

Catch composition, catch per unit effort (CPUE) and species selectivity of fishing gears on multi-species Kaptai Lake in Bangladesh

Kaptai Lake, the largest artificial reservoir in Southeast Asia, is home to a diverse fish fauna that supports thousands of livelihoods and is distinguished by multi-species and multi-gear fisheries. In Kaptai Lake, the gear-based catch composition, catch rate and distribution pattern are little known. From August 2020 to April 2021, a nine-month study was conducted in five upazilas using direct catch assessment surveys and fishing effort surveys from four fishing gears, namely seine nets, gill nets, lift nets, and push nets. A total of 49 morpho-species from 22 families were found, with three species from the Clupeidae accounting for 93.63 % of the catch in all gear combined. The total catch composition and CPUE were higher in seine nets (75.07 %, 13.86 ± 1.8 kg/gear/trip respectively) and lower in lift nets (4.97 %, 1.01 ± 0.21 kg/gear/trip) and showed significant differences among gears, except sampling sites whereas CPUE was higher in Naniarchar for seine nets (17.29 ± 8.89 kg/gear/trip) and lower in Langadu for lift nets (0.62 ± 0.25 kg/gear/trip). Seine nets captured more species, and the number of species increased significantly as CPUE increased. Our study assessed four gears that targeted different fish species with little overlap in leading species; seine nets and gill nets primarily targeted Clupeidae (96.53 % and 41.69 %, respectively), whereas lift nets and push nets primarily targeted Cyprinidae and Palaemonidae (38.93 % and 99.37 % respectively). The observed abundance and variety of fish species captured in gill nets suggest a significant overlap in the selectivity of this fishing method with that of lift nets. Due to the varying contributions of sites and gears, the nMDS ordination pattern reveals a weak spatial variation in catch composition. According to the SIMPER results, Bagridae, Gobiidae, and Ambassidae were the most significant contributors to site grouping patterns across all gears. Furthermore, the findings indicate that the catch composition does not follow the typical pattern of spatial variation. By implementing measures to eliminate or decrease the usage of small mesh nets, there is expected to be a corresponding decrease in the capture of small fish. Additionally, this action will help mitigate the issue of overlapping selectivity among the current fishing gears. Our findings provide baseline data on the potential efficacy of gear limitation and suggest a gear-based management strategy.

Application of environmental DNA metabarcoding to identify fish community characteristics in subtropical river systems

AbstractFish are vital in river ecosystems; however, traditional investigations of fish usually cause ecological damage. Extracting DNA from aquatic environments and identifying DNA sequences offer an alternative, noninvasive approach for detecting fish species. In this study, the effects of environmental DNA (eDNA), coupled with PCR and next‐generation sequencing, and electrofishing for identifying fish community composition and diversity were compared. In three subtropical rivers of southern China, fish specimens and eDNA in water were collected along the longitudinal (upstream–downstream) gradient of the rivers. Both fish population parameters, including species abundance and biomass, and eDNA OTU richness grouped 38 sampling sites into eight spatial zones with significant differences in local fish community composition. Compared with order‐/family‐level grouping, genus‐/species‐level grouping could more accurately reveal the differences between upstream zones I−III, midstream zones IV−V, and downstream zones VI–VIII. From the headwaters to the estuary, two environmental gradients significantly influenced the longitudinal distribution of the fish species, including the first gradient composed of habitat and physical water parameters and the second gradient composed of chemical water parameters. The high regression coefficient of alpha diversity between eDNA and electrofishing methods as well as the accurate identification of dominant, alien, and biomarker species in each spatial zone indicated that eDNA could characterize fish community attributes at a level similar to that of traditional approaches. Overall, our results demonstrated that eDNA metabarcoding can be used as an effective tool for revealing fish composition and diversity, which is important for using the eDNA technique in aquatic field monitoring.

Sensory profiles and market potential of burbot Lota lota maculosa- An emerging aquaculture species

The aquaculture industry needs to increase the diversity of fish species to meet consumers’ escalating demands. Burbot (Lota lota maculosa) has emerged as a promising candidate for such diversification. Nonetheless, a dearth of knowledge exists concerning their sensory characteristics and overall consumer acceptance. This study sought to investigate these crucial aspects, which are instrumental in assessing the market potential of this fish species. A consumer survey was conducted in Idaho from March through July 2017 to initially evaluate burbot's consumer acceptance and market potential. Results showed that over 96% of consumers liked the texture of burbot, 92% liked the flavor of the burbot, and 90% would try burbot again. Significant reasons for consumers’ willingness to eat burbot included cooking preparation, tasty, mild flavor, excellent texture, and excellent flavor. Results from this indicate that burbot is a promising food fish candidate for commercialization. Based on these results, a follow-up panelists survey and sensory analysis were conducted in April 2019 to further investigate consumer acceptance and sensory properties of burbot when compared to other prominent aquaculture species (trout and tilapia). The three species exhibited different sensory profiles; however, burbot was ranked significantly higher for aroma, flavor, and taste. Conversely, panelists found tilapia and trout to be significantly (P <0.05) firmer than burbot for firmness. The results from the sensory testing showed that 87% and 81% of panelists preferred burbot to tilapia and trout, respectively, and 79% would be willing to try this as a new species on the market. The distinct profiles of burbot indicate that this fish species would be highly marketable and if available would contribute to the diversification of U.S. commercial aquaculture by offering a delicate white fillet option to salmonids.

Assessment of PAH Pollution in Mediterranean Lakes and Health Implications for Fish and Consumers, Case Study: Manzala Lake, Egypt

This study aims to investigate the distribution, sources, and compositions of 16 polycyclic aromatic hydrocarbons (PAH) in Manzala Lake water and the organs of two fish species: M. cephalus and O. niloticus. In addition, it aims to assess associated health risks and examine protein pattern responses and histopathological lesions in fish from different lake sectors. ∑PAHs, ∑COMB, and ∑CAR varied between (0.122–51.895), (0.1–49.63), and (0.08–19.949) μg/L, respectively. Many PAH compounds in the water exceeded the guidelines; benzo[a]pyrene in the muscles of O. niloticus exceeded the European Union (EU) guidelines (2 μg/kg), recording 14.18 and 4.59 μg/kg in the eastern and southern sectors, respectively. In general, the ∑PAHs in the muscles of O. niloticus (799.79±26.02 μg/kg) were higher than those of M. cephalus (213.75±8.69 μg/kg) in the eastern sector, which indicates a high potential risk associated with the consumption of O. niloticus. The electrophoresis of protein patterns of the fish muscles recorded site- and species-specific alterations in the proteinogram. M. cephalus exhibited higher sensitivity to PAHs but developed a greater tolerance to PAH contamination than O. niloticus. The histopathological investigation reported several lesions in both fish tissue samples, particularly from the southern sector. Fish from Manzala Lake can pose a carcinogenic risk to consumers, mainly O. niloticus, where the PAH4 carcinogenic index was above the EU guidelines (12 μg/kg) in O. niloticus from all sectors. The study highlights lake management's importance in preserving biodiversity and ensuring food safety.

A non-microcystin-producing Microcystis wesenbergii strain alters fish food intake by disturbing neuro-endocrine appetite regulation

Cyanobacterial harmful algal blooms (cHABs) are pervasive sources of stress resulting in neurotoxicity in fish. A member of the widely distributed Microcystis genus of bloom-forming cyanobacteria, Microcystis wesenbergii can be found in many freshwater lakes, including Dianchi Lake (China), where it has become one of the dominant contributors to the lake's recurrent blooms. However, unlike its more well-known counterpart M. aeruginosa, the effects of dense non-microcystin-containing M. wesenbergii blooms are seldom studied. The disturbance of appetite regulation and feeding behaviour can have downstream effects on the growth of teleost fish, posing a significant challenge to aquaculture and conservation efforts. Here we examined the effects of M. wesenbergii blooms on the food intake of Acrossocheilus yunnanensis, a native cyprinid in southern China. This fish species has disappeared in Dianchi Lake, and its reintroduction might be negatively affected by the presence of this newly-dominant Microcystis species. We co-cultured juvenile A. yunnanensis with a non-microcystin-producing strain of M. wesenbergii at initial densities between 5 × 104 and 1 × 106 cells/mL and monitored fish feeding behaviour and changes in neurotransmitter and hormone protein levels. High-density M. wesenbergii cultures increased the feeding rate of co-cultured fish, elevating concentrations of appetite-stimulating signalling molecules (Agouti-related protein and γ-aminobutyric acid), while decreasing inhibitory ones (POMC). These changes coincided with histopathological alterations and reduced somatic indices in brain and intestinal tissues. Given this potential for detrimental effects and dysregulation of food intake, further studies are necessary to determine the impacts of chronic exposure of M. wesenbergii in wild fish.

Tenascin can inhibit apoptosis induced by copper in silver pomfret (Pampus argenteus)

Silver pomfret, an economically important fish species, encounters significant challenges posed by copper pollution in wild and culturing environment. High level of copper has the potential to accumulate in aquatic organisms over prolonged exposure periods. The extracellular matrix, which is highly susceptible to copper, encompasses various proteins, among which tenascin (TN) might play a crucial role in potentially regulating copper-induced apoptosis. To investigate this hypothesis in fish, we initially identified six TN family members in silver pomfret, namely TNCa, TNCb, TNR, TNXB, TNXBa and TNN. Phylogenetic analysis showed four gene subfamilies, namely TNC, TNR, TNN, and TNX, through comparative analysis with TNs from seven other teleost fish species. Subsequently, we analyzed transcriptome of silver pomfret under copper stress and found differential expression of TN family genes under varying levels of copper stress, particularly TNCa. KEGG enrichment analysis demonstrated a significant enrichment of TN downstream pathway, specifically the Pi3K-AKT signaling pathway. RT-qPCR results indicated up-regulation of TNs and apoptosis inhibition-related genes and down-regulation of apoptosis promotion-related genes within this pathway. Hence, we speculated that TN inhibits copper-induced apoptosis by modulating this particular pathway. To further validate this hypothesis, we established a copper stress cell model using a silver pomfret kidney cell line (PaK) and utilized siRNA to knock down TNCa expression within this cellular model. Comparing RNAi-Cu group to NC-control group, we observed significantly reduced cell viability and intensified apoptosis signals in the former. Additionally, RNAi-Cu group displayed down-regulation of apoptosis inhibition-related genes and up-regulation of apoptosis-related genes in Pi3K-AKT signaling pathway compared to NC-Cu group. These findings indicated that TN might be able to inhibit copper-induced apoptosis through Pi3K-AKT signaling pathway. Ultimately, this study offers foundational knowledge for exploring heavy metal toxicity effect on fishes and some references for utilization of copper in parasite control.

Effect of domestic heat processing techniques on the trace metals concentration in imported frozen fish products in Bayelsa State, Nigeria, and health risk assessment

IntroductionTrace metals in fish play different important roles, both for the fish itself and humans who consume them. However, some of these metals are toxic at low concentrations, and are considered as health hazards. In this study, the concentration of six trace metals (Pb, Cd, Ni, Cu, Mn and Zn) were determined in imported frozen fish species available in Bayelsa State, Nigeria. The effect of domestic heat processing techniques (cooking, frying and smoking) on the trace metals concentration, and the potential risk due to consumption of these metals in fish were also evaluated. MethodsFive different species of imported frozen fish species were purchased from wholesale and retail outlets, and were prepared as raw, cooked, fried and smoked samples. A mixture of acids was used for digestion of fish samples, while Flame atomic absorption spectrometer was used for quantification of metals. The hazard index was employed for evaluating the non-carcinogenic risk of metals in fish. ResultsThe average trace metals concentration in the raw fish samples followed the order: Zn > Cu > Cd > Ni > Mn. Pb was undetected in all fish samples. The concentration of the detected trace metals ranged as follows - Cd: 3.45-9.40 mg/kg, Ni: <0.001-13.13 mg/kg, Cu: 6.10-9.95 mg/kg, Mn: <0.001-1.05 mg/kg, and Zn: 14.50-43.65 mg/kg. The Cd concentration in all raw fish species greatly exceeded its permissible limits. The effect of domestic heat processing techniques on trace metals concentration in fish did not follow any regular pattern, and only Cd concentrations exceeded its permissible limit in all heat processed fish samples. The hazard quotient (HQ) values showed that only Cd had HQ values >1 for both child and adult exposure scenarios. ConclusionThe results suggest trace metal contamination of fish samples by Cd, with significant potential non-carcinogenic risk. Since Cd is toxic, continuous screening of imported fish products is necessary, in order to safeguard public health.

Offshore oil and gas infrastructure plays a minor role in marine metapopulation dynamics

Decommissioning consequences of offshore oil and gas infrastructure removal on marine population dynamics, including connectivity, are not well understood. We modelled the connectivity and metapopulation dynamics of three fish and two benthic invertebrate species inhabiting the natural rocky reefs and offshore oil and gas infrastructure located in the Bass Strait, south-east Australia. Using a network approach, we found that platforms are not major sources, destinations, or stepping-stones for most species, yet act as modest sources for connectivity of Corynactis australis (jewel anemone). In contrast, sections of subsea pipelines appear to act as stepping-stones, source and destination habitats of varying strengths for all study species, except for Centrostephanus rodgersii (long-spined sea urchin). Natural reefs were the main stepping-stones, local source, and destination habitats for all study species. These reefs were largely responsible for the overall metapopulation growth of all study species (average of 96 % contribution across all species), with infrastructure acting as a minor contributor (<2 % average contribution). Full or partial decommissioning of platforms should have a very low or negligible impact on the overall metapopulation dynamics of the species explored, except C. australis, while full removal of pipelines could have a low impact on the metapopulation dynamics of benthic invertebrate species and a moderate impact on fish species (up to 34.1 % reduction in the metapopulation growth). We recommend that the decision to remove offshore infrastructure, either in full or in-part, be made on a platform-by-platform basis and consider contributions of pipelines to connectivity and metapopulation dynamics.

Global patterns of nuclear and mitochondrial genetic diversity in marine fishes.

Genetic diversity is a fundamental component of biodiversity. Examination of global patterns of genetic diversity can help highlight mechanisms underlying species diversity, though a recurring challenge has been that patterns may vary by molecular marker. Here, we compiled 6862 observations of genetic diversity from 492 species of marine fish and tested among hypotheses for diversity gradients: the founder effect hypothesis, the kinetic energy hypothesis, and the productivity-diversity hypothesis. We fit generalized linear mixed effect models (GLMMs) and explored the extent to which various macroecological drivers (latitude, longitude, temperature (SST), and chlorophyll-a concentration) explained variation in genetic diversity. We found that mitochondrial genetic diversity followed geographic gradients similar to those of species diversity, being highest near the Equator, particularly in the Coral Triangle, while nuclear genetic diversity did not follow clear geographic patterns. Despite these differences, all genetic diversity metrics were correlated with chlorophyll-a concentration, while mitochondrial diversity was also positively associated with SST. Our results provide support for the kinetic energy hypothesis, which predicts that elevated mutation rates at higher temperatures increase mitochondrial but not necessarily nuclear diversity, and the productivity-diversity hypothesis, which posits that resource-rich regions support larger populations with greater genetic diversity. Overall, these findings reveal how environmental variables can influence mutation rates and genetic drift in the ocean, caution against using mitochondrial macrogenetic patterns as proxies for whole-genome diversity, and aid in defining global gradients of genetic diversity.

Molecular taxonomy of fish larvae in the Northwestern Arabian gulf: A baseline study from Kuwait's first marine protected area

Sulaibikhat Bay, a shallow embayment dominated by tides and extensive mud flats along the northern coast of Kuwait Bay, serves as a crucial nursery ground for various commercially important species of finfish and shellfish in the Northwestern Arabian Gulf (NWAG). As the location of Kuwait's inaugural marine protected area (MPA), Sulaibikhat Bay plays a vital role in fostering numerous fish and marine invertebrate species of commercial importance in the Arabian/Persian Gulf. Accurate identification of larval specimens from this habitat is essential for understanding their spawning dynamics and recruitment process. However, limitations in taxonomic identification hinder scientific understanding of fish larval recruitment. To address this, our baseline study employed an integrated taxonomic approach, combining conventional morphology with molecular techniques. Fish larvae collected from the MPA and surrounding waters in Spring (2022) were identified up to the genus and species levels using partial gene sequencing of 16 S rRNA and mitochondrial cytochrome oxidase (COI) genes. Morphological analysis indicated the prevalence of Sparidae, Sillaginidae, and Dorosomatidae families. Molecular analysis confirmed the presence of these families and identified two species, Crenidens crenidens (Sparidae) and Nematalosa nasus (Dorosomatidae), along with two genera, Diplodus sp. (Sparidae) and Sillago sp. (Sillaginidae), which exhibited maximum similarity to available COI sequences of Diplodus sargus, and Sillago maculata, respectively. This represents the first baseline molecular study on fish larvae from NWAG, laying the groundwork for future in-depth analyses with more larval specimens and spatiotemporal samplings from the entire exclusive economic zone (EEZ) of Kuwait in the Arabian/Persian Gulf.

Bioaccumulation of Heavy Metals in Five Species of Fish Obtained from the Estuary of Rabat, Morocco

Bioaccumulation of Heavy Metals in Five Species of Fish Obtained from the Estuary of Rabat, Morocco

Nutrients monitoring on the Bui multipurpose dam project in the Savannah region of Ghana

Monitoring the nutrient levels of the dam water on the Bui hydropower project (Ghana) is vital for understanding its ecological health. The purpose of this study is to evaluate current (2021) nutrient levels and examine the irrigational water quality. The novelty of this research lies in the combination of nutrient analysis and irrigational water quality index (IWQI) as tool to understand the ecological health of the dam water. Bui dam water is slightly acidic (pH of 6.6) which partly influences nutrient bioavailability in the dam water. The composition of water in terms of ion dominance follow the order of Ca2+>Na+>Mg2+>K+ and that of anions followed the order of HCO3->Cl->SO42->NO3-, with signatures of Ca2+- Mg2+- HCO3– water type. Pearson’s correlation plot shows pH, TDS, and EC influences sulphate distribution in the dam. EC mean level of 78.06 µS/cm is below acceptable ranges (150 and 500 µS/cm) known to sustain freshwater fish species (e.g., Alestidae, Anabantidae and Bagridae family) present in the Bui dam. Historical nitrate, phosphate and sulphate measured 2.01mgL-1, 0.16mgL-1 and 20.96mgL-1 as against 0.79mgL-1, 0.60mgL-1 and 2.22mgL-1 caused by the impoundment. The nutrient decrease shows improved water quality over time. The spatial plot shows low phosphate levels in the northwestern and southeastern part of the dam indicating rapid uptake and sediment trapping. IWQI shows the water has no toxicity risk for any plant. This study provides a basis for further monitoring to ensure the observed nutrient decrease is not altered by human-induced activities. Strengthening management policies is therefore encouraged to sustain the dam’s ecological health.

CXCL13/CXCR5 axis mediates IgM+ B cell migration through AKT and STAT3 signaling pathways in Nile tilapia (Oreochromis niloticus)

Chemokine C-X-C motif ligand 13 (CXCL13), originally identified as a B-lymphocyte chemokine, exerts a crucial role in the chemotaxis of B cells through its receptor CXCR5. Although the presence of CXCL13/CXCR5 had been reported in various teleost fish species, its impact on IgM+ B cell still remains unknown. In this study, we investigated the role of chemokine CXCL13 and its receptor CXCR5 in the chemotaxis of IgM+ B cells in Nile tilapia (Oreochromis niloticus). We identified and characterized two isotypes of OnCXCL13 (OnCXCL13a and OnCXCL13b) and CXCR5 (OnCXCR5) in Nile tilapia. The OnCXCL13 is characterized with a typical small cytokine CXC domain and four cysteine, in which the first two cysteines separated by a random amino acid residue, and OnCXCR5 is characterized by seven α-helical transmembrane domains. Both OnCXCL13 and OnCXCR5 were found to be expressed in various tissues and lymphocytes, with the highest expression in the spleen (SPL). Their expression in IgM+ B cells was significantly higher than that in IgM− lymphocytes. Following Streptococcus agalactiae infection, the expressions of OnCXCL13a and OnCXCL13b were up-regulated in peripheral blood (PBL), SPL and head kidney (HK), while OnCXCR5 was significantly up-regulated in SPL and HK. We also found that the recombinant OnCXCL13 proteins had strong chemotactic activity on IgM+ B cells, which could be inhibited by blocking OnCXCR5 with anti-OnCXCR5 antibody. Mechanistically, incubation with OnCXCL13 resulted in the up-regulation of AKT and STAT3 phosphorylation in IgM+ B cells, which could be attenuated by specific inhibitors of AKT and STAT3. Inhibition of AKT and STAT3 also weakened the chemotaxis of OnCXCL13 on IgM+ B cells. Our results suggest that the CXCL13/CXCR5 axis participates in the immune response of tilapia and mediates the chemotaxis of IgM+ B cells, providing insights into the potential role of this axis in bacterial infection and teleost B cell migration.

Extracellular traps in skin lesions infected with lymphocystis disease virus in black rockfish (Sebastes schlegelii)

The lymphocystis disease (LCD), caused by Lymphocystis disease virus (LCDV), is a benign and self-limiting disease described in a many freshwater and marine fish species. Hypertrophic fibroblasts and extensive aggregation of inflammatory cells are characteristics of LCD. In the present study, small animal imaging and ultrastructural investigations were carried out on the lymphocystis nodules of black rockfish (Sebastes schlegelii) naturally infected with lymphocystis iridovirus, to assess pathology, and the exudate with particular attention to the formation of extracellular traps (ETs) in vivo. Ex vivo were examined by nodules sections and primary cells stimulation. By histopathological analysis, the nodules contained infiltrated inflammatory cells and extensive basophilic fibrillar filaments at the periphery of the hypertrophied fibroblasts. ETs were assessed in nodules samples using indirect immunofluorescence to detect DNA and myeloperoxidase. Moreover, LCDV was able to infect peritoneal cells of black rockfish in vitro and induce the formation of ETs within 4 hours. In summary, this study proved that ETs are involved in the response to LCDV infection and may be involved in formation of lymphoid nodules. Taken together, the findings provide a new perspective to determine the impact factors on the growth of nodules.

Mapping the occurrence of Eustrongylides spp. in fish species caught from six lakes in Central Italy (Tuscany and Latium regions): Implications for local fishery supply chains

In the present study, in order to expand the knowledge on the distribution of parasites of the genus Eustrongylides in never investigated Italian lacustrine areas of Tuscany and Latium, fish specimens from four Tuscan lakes (Bilancino, Chiusi, Montedoglio and San Cipriano) and two Latium lakes (Bolsena and Bracciano) were collected and analyzed. The parasitological analysis, consisting of a visual inspection followed by a chloro-peptic digestion, was performed on 1650 specimens belonging to 17 species: European perch (Perca fluviatilis), Pumpkinseed (Lepomis gibbosus), Pike-perch (Sander lucioperca), Largemouth black bass (Micropterus salmoides), Pike (Esox lucius), Big-scale sand smelt (Atherina boyeri), Tench (Tinca), European Whitefish (Coregonus lavaretus), Channel catfish (Ictalurus punctatus), Chub (Squalius cephalus), Rudd (Scardinius erythrophthalmus), Common bleak (Alburnus alborella), South European roach (Sarmarutilus rubilio), South European nase (Protochondrostoma genei), Italian riffle dace (Telestes muticellus), Goldfish (Carassius auratus), and Freshwater bream (Abramis brama). Eustrongylides spp. larvae were only found in one specimen of European perch caught in Bracciano Lake and purchased from a local fishmonger (P = 3.3%; MI = 1; MA = 0.03). The only isolated Eustrongylides spp. larva was submitted to molecular analysis of the ITS gene region and identified as E. excisus. This finding adds Bracciano Lake to the list of the several Italian lakes in which nematodes belonging to this genus have been reported. Even if the observed prevalence is currently low, the presence of the parasite in this local freshwater fish supply chain requires FBOs to adopt risk management measures to prevent contaminated products from reaching final consumer. Moreover, future investigations will show if the parasite expands in these areas.

Establishment and characterization of cell line from fin of Chinense bahaba (Bahaba taipingensis) and transcriptome analysis of its response to megalocytivirus SKIV-SD strain infection

The Chinese bahaba (Bahaba taipingensis) is an endangered fish species with high economic value, found in the southeastern sea of China. In this study, we established the first Chinese bahaba cell line, named BTF, derived from fin tissue. The primary cells were cultured for over 55 passages in L-15 medium with 15% FBS at 27 °C. These cells exhibited a fibroblast-like morphology with multipolar shapes. Karyotype testing revealed a chromosome number of 2n = 48. After thawing the cells that had been stored in liquid nitrogen for 10 months, their viability was >80%. The cell was separately transfected with EGFP-N3 plasmid and cy3 labeled scramble siRNA and clear fluorescence were observed. Moreover, the cells displayed sensitivity to megalocytivirus SKIV-SD strain, demonstrating a pronounced cytopathic effect (CPE) 24 h after infection. Transcriptome sequencing analysis of SKIV-SD infected cells revealed highly expressed genes significantly enriched in nucleic acid replication and protein translation-related pathways, such as Ribosome biogenesis, RNA polymerase, Nucleocytoplasmic transport, and DNA replication. In addition, the infected cells showed differential expression of immune-related genes such as cxcr4 and dr5, which are involved in virus infection. In conclusion, the BTF cell line, derived from the fin tissue of the Chinese bahaba, exhibits stable growth and can be stored in liquid nitrogen for extended periods. This cell line plays a crucial role in conserving the germplasm resources of Chinese bahaba and will serve as a valuable reference for establishing cell lines from other tissues of the Chinese bahaba. Furthermore, our findings suggest that this cell line holds significant potential for virology research, foreign protein expression, and in vitro biological studies of Chinese bahaba.

Enhancing migratory potential in fish passes: The role of pier shape in minimizing debris accumulation

Biodiversity preservation is a primary challenge of the 21st century, focusing on restoring unobstructed river flows and mitigating the effects of barriers, supported by European biodiversity strategies up to 2030. Maintaining ecological continuity, such as unblocking fishways clogged by floating debris disrupting natural fish migration paths, remains a challenge despite conventional protective methods. This study, taking a vertical slot fish pass in Wrocław on the Odra River as a case study and based on research on bridge piers, suggests modifying pier shapes from rectangular to rounded in order to reduce debris accumulation. Field studies, utilizing an OTT MF Pro flow meter, were conducted to validate the numerical model. The measured flow rate in the field was 3.15 [m³·s−1], while the numerical modeling yielded a flow of 3.19 [m³·s−1]. Focusing on optimizing the shape of cross-wall piers to enhance fish migration conditions, the study examined six different pier configurations, analyzing flow speed in the main slot, crucial for migration. Using 2D hydraulic modeling with Iber, it assessed the migratory potential of different pier designs by analyzing hydraulic conditions and comparing them with the swimming capabilities of fish species native to the Odra River. Results indicate that rounding the pier edges positively affects flow speeds in the main slot, enhancing fish migration possibilities, contributing to fish pass functionality improvement and supporting broader biodiversity and ecosystem health goals.

PREVALENCE OF OPECOELID TREMATODES (TREMATODA: DIGENEA: OPECOELIDAE) IN THE WOOLLY SCULPIN CLINOCOTTUS ANALIS FROM THE PACIFIC COAST OF THE BAJA CALIFORNIA PENINSULA.

Prevalence values for 3 digenean species of the family Opecoelidae were calculated during a half-year period from 20 individuals per month of the fish species Clinocottus analis, collected from an intertidal environment of Baja California, Mexico. Trematode species recovered were Opecoelus adsphaericus, Opecoelus cameroni, and Opecoelus pacificus. Of these, only O. adsphaericus was present throughout the study, whereas O. pacificus and O. cameroni were recorded for 1 or 2 mo, respectively, exhibiting relatively low prevalence values. The decrease in prevalence of O. adsphaericus coincides with the appearance of O. pacificus and O. cameroni; these last 2 species were found only in the largest hosts, and their presence represents new records for Mexican marine fauna.

Automated escape system: identifying prey's kinematic and behavioral features critical for predator evasion.

Identifying the kinematic and behavioral variables of prey that influence the evasion from predator attacks remains challenging. To address this challenge, we have developed an automated escape system that responds quickly to an approaching predator and pulls the prey away from the predator rapidly, as real prey. Reaction distance, response latency, escape speed, and other variables can be adjusted in the system. By repeatedly measuring the response latency and escape speed of the system, we demonstrated the system's ability to exhibit fast and rapid responses while maintaining consistency across successive trials. Using the live predatory fish species, Coreoperca kawamebari, we show that escape speed and reaction distance significantly affect the outcome of predator-prey interactions. These findings indicate that the developed escape system is useful for identifying kinematic and behavioral features of prey that are critical for predator evasion, as well as for measuring the performance of predators.