Search Results (175)

Corner separation at the junction of blade surfaces and end walls remains a significant challenge in compressor cascade performance. This study proposes a passive flow control strategy inspired by the geometric arrangement of biological fish scales to address this issue. A fish scale-like surface structure was applied to the suction side of a cascade blade to reduce viscous drag and modulate secondary flow behavior. Wind tunnel experiments and numerical simulations were conducted to evaluate its aerodynamic effects. The results show that the fish scale-inspired configuration induced climbing vortices that energized low-momentum fluid near the end wall, effectively suppressing both passage and corner vortices. This led to a reduction in spanwise flow penetration and a decrease in total pressure loss of up to 5.69%. The enhanced control of secondary flows also contributed to improved flow uniformity in the end-wall region. These findings highlight the potential of biologically inspired surface designs for corner vortex suppression and aerodynamic efficiency improvement in turbomachinery systems. Full article

Black rockfish (Sebastes schlegelii) is a marine ovoviviparous teleost that exhibits significant sexual dimorphism, with females growing faster and reaching larger sizes than males. Establishing stable oogonial stem cells (OSCs) is critical for understanding germline stem cell dynamics and facilitating all-female breeding. In this study, we successfully isolated and cultured OSCs from S. schlegelii for 12 passages. These cells exhibited alkaline phosphatase activity, expressed germline marker genes (ddx4, cdh1, klf4), and maintained a diploid karyotype (2n = 48). Transcriptomic comparisons between early (P3) and late (P12) passages revealed significant metabolic dysfunction and cell cycle arrest in the late-passage cells. Specifically, the down-regulation of glutathione-related and glycolysis-related genes (gstm3, gstt1, mgst3, gsta1, gsta4, gsto1, gapdh) and key mitotic regulators (cdk1, chk1, cdk4, e2f3, ccne2, ccnb1) suggested that metabolic imbalance contributes to oxidative stress, resulting in cell cycle inhibition and eventual senescence. This study provides a marine fish model for investigating metabolism-cell cycle interactions in germline stem cells and lays the foundation for future applications in germ cell transplantation and all-female breeding. Full article

Effective monitoring of fish passage through river barriers is essential for evaluating fishway performance and supporting adaptive river management. Traditional methods are often invasive, labor-intensive, or too costly to enable widespread implementation across most fishways. Infrared (IR) beam-break counters offer a promising alternative, but their adoption has been limited by high costs and a lack of flexibility. We developed and tested a novel, low-cost infrared beam-break counter—FishTracker—based on open-source Raspberry Pi and Arduino platforms. The system detects fish passages by analyzing interruptions in an IR curtain and reconstructing fish silhouettes to estimate movement, direction, speed, and morphometrics under a wide range of turbidity conditions. It also offers remote access capabilities for easy management. Field validation involved controlled tests with dummy fish, experiments with small-bodied live specimens (bleak) under varying turbidity conditions, and verification against synchronized video of free-swimming fish (koi carp). This first version of FishTracker achieved detection rates of 95–100% under controlled conditions and approximately 70% in semi-natural conditions, comparable to commercial counters. Most errors were due to surface distortion caused by partial submersion during the experimental setup, which could be avoided by fully submerging the device. Body length estimation based on passage speed and beam-interruption duration proved consistent, aligning with published allometric models for carps. FishTracker offers a promising and affordable solution for non-invasive fish monitoring in multispecies contexts. Its design, based primarily on open technology, allows for flexible adaptation and broad deployment, particularly in locations where commercial technologies are economically unfeasible. Full article

Hydropower infrastructure has profoundly altered riverine connectivity, posing challenges to the migratory behavior of aquatic species. This study examined the post-passage migration efficiency of Schizothorax wangchiachii in a regulated river system, focusing on upstream and downstream reaches of the Songxin Hydropower Station on the Heishui River, a tributary of the Jinsha River. We used radio-frequency identification (RFID) tagging to track individuals after fishway passage and coupled this with environmental monitoring data. A Cox proportional hazards model was applied to identify key abiotic drivers of migration success and to develop a predictive framework. The upstream success rate was notably low (15.6%), with a mean passage time of 438 h, while downstream success reached 81.1%, with an average of 142 h. Fish exhibited distinct diel migration patterns; upstream movements were largely nocturnal, whereas downstream migration mainly occurred during daylight. Water temperature (HR = 0.535, p = 0.028), discharge (HR = 0.801, p = 0.050), water level (HR = 0.922, p = 0.040), and diel timing (HR = 0.445, p = 0.088) emerged as significant factors shaping the upstream movement. Our findings highlight that fishways alone may not ensure functional connectivity restoration. Instead, coordinated habitat interventions in upstream tributaries, alongside improved passage infrastructure, are crucial. A combined telemetry and modeling approach offers valuable insights for river management in fragmented systems. 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

To help fish to bypass dams and other human-made barriers, some fishways have ingeniously incorporated extended tunnel sections. This innovative design not only optimizes the overall structure of the fishway but also significantly reduces disturbances to the surrounding ecosystem. However, the potential challenges posed by long tunnel sections to fish upstream migration remain insufficiently studied and poorly understood. This study conducted in situ experiments utilizing a passive-integrated-transponder (PIT) system to quantitatively assess the effects of dark and natural light environments on the upstream migration behavior of plateau-endemic fishes (Schizothorax macropogon, Schizothorax waltoni, and Schizothorax oconnori) in a vertical-slot fishway. A 655 m section of the fishway was selected for the experiment, with shading cloth used to simulate the dark environment (DE) of tunnel sections, and its removal serving as the natural light environment (NE). The results showed that in the DE, the upstream behaviors of S. macropogon, S. waltoni, and S. oconnori were not hindered. The entry efficiency at the experimental segment (Ee) of all three species exceeded 65% in the DE, which was higher than that in the NE. The passage efficiency (Ep) of S. macropogon and S. waltoni showed no significant difference between the DE and NE, whereas S. oconnori exhibited a significant difference, with an overall Ep of 0% in the NE and 75.0% in the DE. Additionally, the DE caused a temporary disruption to the diel migration rhythms of the three species. The transit speeds (St) of S. macropogon and S. waltoni were both elevated in the DE, with S. waltoni showing a particularly significant increase; its average St in the DE (0.080 m/s) was much higher than in the NE (0.021 m/s). Ridge regression analysis further indicated that the DE was the primary factor influencing the St and had a positive effect on upstream behavior. Moreover, differences in the upstream migration performances of different species under varying light conditions highlighted species-specific sensitivity to light. This study offers key insights for fish passage design in canyon hydropower projects and highlights the potential of tunnel-type fishways in restoring river connectivity. Full article

The vertical slot fishway (VSF) has proven effective in mitigating the severe fragmentation of rivers caused by artificial hydraulic structures. While fishways with steeper slopes exhibit better economic performance, increased slope can raise the flow velocity and turbulence, which may hinder fish migration. To address this issue, this study investigated the application of a VSF with a staggered baffle configuration. Through numerical modeling, the hydraulic characteristics of the VSF under various slope ratios and chamber length-to-width (L/B) ratios were investigated, with data validated by physical models. An increase in the slope gradient resulted in higher flow velocities, greater maximum attenuation rates of mainstream velocity, and elevated turbulent kinetic energy (TKE) at the corners of the rectifier baffles and the ends of the divider baffles. Additionally, the overall maximum volumetric energy dissipation ($D_{\epsilon }$) increased, although its distribution pattern remained unaffected. Conversely, increasing the chamber L/B ratio significantly altered the distribution patterns of the flow velocity, TKE, and $D_{\epsilon }$, influencing their generation mechanisms. For instance, a higher chamber L/B ratio caused the maximum flow velocity (V_m) to deviate from the vertical slot and raised the maximum attenuation rate of the mainstream velocity. The L/B ratio also caused changes in the TKE distribution; as the ratio increased, the proportion of the chamber’s internal region with $D_{\epsilon }\le 150 \mathrm{W}/{\mathrm{m}}^3$ initially decreased and then increased. Overall, considering the flow velocity, TKE, and $D_{\epsilon }$, it is recommended that the chamber L/B ratio be maintained between 0.9 and 1.1 for slope ratios ranging from 1:20 to 1:50. The research results will offer practical insights for engineering applications, in engineering construction, contribute theoretical guidance for the optimized design of fish passages, promote sustainable hydraulic engineering practices, and aid in the protection of aquatic biodiversity. Full article

The field of computer vision has progressed rapidly over the past ten years, with noticeable improvements in techniques to detect, locate, and classify objects. Concurrent with these advances, improved accessibility through machine learning software libraries has sparked investigations of applications across multiple domains. In the areas of fisheries research and management, efforts have centered on the localization of fish and classification by species, as such tools can estimate the health, size, and movement of fish populations. To aid in the interpretation of computer vision for fisheries research management tasks, a survey of the recent literature was conducted. In contrast to prior reviews, this survey focuses on employed evaluation metrics and datasets as well as the challenges associated with applying machine learning to a fisheries research and management context. Misalignment between applications and commonly used evaluation metrics and datasets mischaracterizes the efficacy of emerging computer vision techniques for fisheries research and management tasks. Aqueous, turbid, and variable lighted deployment settings further complicate the use of computer vision and generalizability of the reported results. Informed by these inherent challenges, culling surveillance data, exploratory data collection in remote settings, and selective passage and traps are presented as opportunities for future research. Full article

Recent advances in fish transportation technologies and deep machine learning-based fish classification have created an opportunity for real-time, autonomous fish sorting through a selective passage mechanism. This research presents a case study of a novel application that utilizes deep machine learning to detect partially dewatered fish exiting an Archimedes Screw Fish Lift (ASFL). A MobileNet SSD model was trained on images of partially dewatered fish volitionally passing through an ASFL. Then, this model was integrated with a network video recorder to monitor video from the ASFL. Additional models were also trained using images from a similar fish scanning device to test the feasibility of this approach for fish classification. Open source software and edge computing design principles were employed to ensure that the system is capable of fast data processing. The findings from this research demonstrate that such a system integrated with an ASFL can support real-time fish detection. This research contributes to the goal of automated data collection in a selective fish passage system and presents a viable path towards realizing optical fish sorting. Full article

Dams severely affect aquatic environments and block the longitudinal migration of fish. In order to mitigate the negative effects generated by these developments, fish passes, or fishways, are implemented in dams with the purpose of restoring river connectivity and allowing the movement of migrants. Nevertheless, fishways in neotropical areas often face design and construction issues that can reduce their efficiency and selectively disadvantage species with limited swimming capabilities. This study analyzes how a fish ladder on the Paraná River influences the black armored catfish (Rhinelepis aspera), a benthic, long-distance migratory species important to commercial fisheries. A total of 200 individuals were PIT-tagged and monitored for four months. The results showed that although many fish successfully located the fishway, only a small portion (3.5%) managed to complete the ascent. The interaction between the hydraulic characteristics of the fishway and the fish condition factor played a significant role in ascent performance. Our findings underscore the importance of assessing fishway suitability for benthic neotropical species to support conservation efforts in the Upper Paraná River Basin. To improve passage rates for R. aspera, we recommend optimizing flow conditions by adjusting orifice and notch configurations, incorporating roughness elements, and modifying resting pool designs. These adaptations would reduce energy expenditure for ascending fish, enhancing fishway performance and contributing to the sustainability of migratory species in this region. Full article

Fish need to make different responses to different water flow conditions, as a variety of fish utilize or overcome the water flow while fish are in the water. This study aims to analyze the response of two types of carp (black carp and silver carp) to water flow in different body lengths (2.0–10.0 cm) in early developmental stages in an open channel. By analyzing the water velocity and fish swimming behavior, swimming against the water flow was the most frequent swimming behavior, and the frequencies of this behavior increased with the increased body length of fish. The results demonstrated that the detectable water velocity of two carp species of different body lengths remained in a certain range (0.020–0.060 m/s). Black carp and silver carp can swim against the water flow of 0.295–0.790 m/s and 0.245–0.825 m/s, respectively. The results of this study can provide invaluable data for engineers and biologists to protect fish in the early developmental stage and restore the ecological habitats in the regulated river systems. Full article

The orange-spotted grouper (Epinephelus coioides) is an important mariculture fish in China. However, in recent years, with the rapid development of aquaculture activities, outbreaks of viral diseases have affected the grouper aquaculture industry, causing severe economic losses. In the present study, we isolated and identified a virus from diseased, orange-spotted groupers from an aquaculture farm in Hainan Province, China. The isolated virus was identified as orange-spotted grouper iridovirus, hence named the orange-spotted grouper iridovirus Hainan strain (OSGIV-HN-2018-001). OSGIV-HN-2018-001 induces a cytopathic effect after the infection of mandarin fish (Siniperca chuatsi) brain clonal passage (SBC) cells. In addition, the cytoplasm of the OSGIV-HN-2018-001-infected SBC cells was found to contain a large number of hexagonal virus particles with a diameter of approximately 134 nm. Using the Illumina NovaSeq system, we assembled the sequence data and annotated the complete genome of OSGIV-HN-2018-001 (GenBank accession number: PP974677), which consisted of 110,699 bp and contained 122 open reading frames (ORFs). Phylogenetic tree analysis showed that OSGIV-HN-2018-001 was most closely related to ISKNV-ASB-23. The cumulative mortality rate of groupers infected with OSGIV-HN-2018-001 reached 100% on day 8. The spleens were enlarged and blackened after the dissection of the dying groupers. These results contribute to the understanding of the molecular regulatory mechanism of the iridovirus infection and provide a basis for iridovirus prevention. Full article

Fish passage facilities are essential for restoring river connectivity and protecting ecosystems, effectively balancing economic and ecological benefits. Systematic and comprehensive monitoring, assessment, and optimized management are therefore crucial. This study quantitatively evaluated the entire upstream migration process of fish from the downstream river to the entrance and exit of the fishway and investigated the upstream movement patterns of fish under various environmental factors. A total of 19 fish species were monitored in the Heishuihe River downstream of the dam, with 15 species reaching the fishway entrance and 12 species successfully passing through it. The entrance attraction and passage rates of the vertical-slot fishway at the Songxin hydropower station were 15.7% and 40.42%, respectively. The best upstream performance was observed in May, with fish demonstrating better upstream timing and speed during nighttime compared to daytime. Specifically, the highest entrance attraction efficiency was recorded at a flow rate of 6–7 m³/s and a temperature of 19–20 °C, while the optimal passage efficiency was observed at a flow rate of 0–0.5 m³/s and a temperature of 17–20 °C. Additionally, a multifactorial Cox proportional hazards regression model was constructed to identify key factors influencing the probability of fishway entrance attraction and successful passage. The model elucidated the impact patterns of these key factors on fish upstream migration, ultimately generating an alignment diagram for prediction and control. This study provides a theoretical foundation and data support for developing optimized operational schedules for fishways. The findings offer a more comprehensive and systematic approach for monitoring and evaluating fish passage facilities, serving as a scientific basis for ecological restoration and fish conservation in this region and similar areas. Full article

Coastal ecosystems are facing critical water quality deterioration, while the most convenient passage to the South China Sea, Beibu Gulf, has been under considerable pressure to its ecological environment due to rapid development and urbanization. In this study, we characterized the spatiotemporal change in the water quality in Beibu Gulf and proposed a machine learning approach to predict the water pollution level in Beibu Gulf on the basis of 5-year (2018–2022) observation data of ten water quality parameters from ten selected sites. Random forest (rf) and linear algorithms were utilized. Results show that a high frequency of exceedance of water quality parameters was observed particularly in summer and autumn, e.g., the exceeding rate of Dissolved Inorganic Nitrogen (DIN) at GX01, GX03, GX06, and GX07 station were 28.2~78.1% (average is 52.0%), 6.0~21.7% (average is 52.0%), 23.0~44.7% (average is 31.9%), and 5.2~33.4% (average is 21.2%), respectively. With regard to the spatial distribution, the pH, Water Salinity (WS), and Dissolved Oxygen (DO) values of stations inside the bay were overall lower than those of corresponding stations at the mouth of the bay and stations outside the bay. The concentrations of Chlorophyll-a concentration (except QZB) and nutrient salts showed a clearly opposite trend compared with the above concerned three parameters. For instance, the average Chl-a value of station GX09 was 22.5% higher than that of GX08 and GX10 between 2018 and 2022. Correlation analysis among water quality factors shows a significant positive correlation (r > 0.85) between Dissolved Inorganic Nitrogen (DIN) and NO₃-N, followed by NO₂-N and NH₄-N, indicating that the main component of DIN is NO₃-N. The forecasting results with machine learning also demonstrate the possibility to estimate the water quality parameters, such as chl-a concentration, DIN, and NH₄-N in a cost-effective manner with prediction accuracy of approximately 60%, and thereby could provide near-real-time information to monitor the water quality of the Beibu Gulf. Predicting models initiated in this study could be of great interest for local authorities and the tourism and fishing industries. Full article

The hydrodynamics at the fishway entrance play an important role in attracting fish into a fishway. Adjusting the entrance angle of the fishway to allow suitable water flow patterns at the entrance is an effective measure that can be used to improve the attraction efficiency. In this study, we analyzed the movement behavior of grass carp (Ctenopharyngodon idella) in a river channel at a fishway entrance with different fishway entrance angles (30°, 45°, and 60°) and different replenishment velocities (0.1 m/s, 0.2 m/s, and 0.3 m/s). The flow velocity was 0.32–0.50 m/s when the fish head deflected into the entrance under different entrance angles for grass carp. As the entrance angle of the fishway increased, the fish energy consumption increased. The range of energy consumption for grass carp increased from 1.26–3.59 × 10⁻³ J to 3.32–7.33 × 10⁻³ J when the entrance angle was increased from 30° to 60°. There was a negative correlation between the entrance angle of the fishway and the deflection angle of the tested fish’s head. This research presents a reference that combines fish swimming behavior and hydraulics to optimize the design of fishway entrances. Full article