Death Of Fish Research Articles

A Transcriptomic Study Reveals That Fish Vibriosis Due to the Zoonotic Pathogen Vibrio vulnificus Is an Acute Inflammatory Disease in Which Erythrocytes May Play an Important Role

Vibrio vulnificus is a marine zoonotic pathogen associated with fish farms that is considered a biomarker of climate change. Zoonotic strains trigger a rapid death of their susceptible hosts (fish or humans) by septicemia that has been linked to a cytokine storm in mice. Therefore, we hypothesize that V. vulnificus also causes fish death by triggering a cytokine storm in which red blood cells (RBCs), as nucleated cells in fish, could play an active role. To do it, we used the eel immersion infection model and then analyzed the transcriptome in RBCs, white BCs, and whole blood using an eel-specific microarray platform. Our results demonstrate that V. vulnificus triggers an acute but atypical inflammatory response that occurs in two main phases. The early phase (3 h post-infection [hpi]) is characterized by the upregulation of several genes for proinflammatory cytokines related to the mucosal immune response (il17a/f1 and il20) along with genes for antiviral cytokines (il12β) and antiviral factors (ifna and ifnc). In contrast, the late phase (12 hpi) is based on the upregulation of genes for typical inflammatory cytokines (il1β), endothelial destruction (mmp9 and hyal2), and, interestingly, genes related to an RNA-based immune response (sidt1). Functional assays revealed significant proteolytic and hemolytic activity in serum at 12 hpi that would explain the hemorrhages characteristic of this septicemia in fish. As expected, we found evidence that RBCs are transcriptionally active and contribute to this atypical immune response, especially in the short term. Based on a selected set of marker genes, we propose here an in vivo RT-qPCR assay that allows detection of early sepsis caused by V. vulnificus. Finally, we develop a model of sepsis that could serve as a basis for understanding sepsis caused by V. vulnificus not only in fish but also in humans.

A Review of Abdominal Dehydration (Dropsy)

Any factor that upsets the hemostatic balance of the existing body creates a condition called disease. Each group of pathogens has specific symptoms in fish, in other words, in general, the behavior and appearance of sick fish is different from healthy fish. Dropsy is one of the most ugly and difficult diseases of aquarium fish. Almost all types of aquarium fish can be infected with this disease, which unfortunately leads to the death of fish in 99% of cases. This disease is one of the easiest diseases to diagnose. But it can be said that it gives almost no response to treatment.

Comparison of modes of action between fish, cell and mitochondrial toxicity based on toxicity correlation, excess toxicity and QSAR for class-based compounds

Mitochondria are significant targets in cells for many environmental chemicals. Mitochondrial damage and dysfunction can lead to apoptosis and death of fish. The objectives of this study were to compare the modes of action (MOAs) between fish, cell and mitochondrial toxicity. To achieve the goal, toxicity correlation, excess toxicity and quantitative structure–activity relationship (QSAR) were investigated between these three toxicity endpoints for a wide range of compounds. Results showed that fish toxicity is well correlated to cytotoxicity, but overall fish toxicity is relatively greater than the cytotoxicity. On the other hand, fish or cell toxicity is poorly related to mitochondrial toxicity, suggesting some compounds share same toxic mechanism but some not. The excess toxicity calculated from toxicity ratio (TR) shows that specifically-acting compounds in cytotoxicity, such as insecticides, fungicides, herbicides, dyes and medications used to treat cancer, depression, heart failure and blood pressure, are active compounds in mitochondrial toxicity. However, the less inert compounds identified in fish and cell toxicity exhibit greatly mitochondrial toxicity. QSAR models reveal that fish or cell toxicity is closely related to the chemical hydrophobicity, ionization, energy of lowest unoccupied molecular orbital, hydrogen bonding potential and stability. These descriptors reflect chemical bio-uptake, reactivity and interaction with target receptors. On the other hand, binomial model reveals that mitochondrial toxicity is closely related to the chemical hydrophobicity and polarizability/dipolarity, indicating bio-uptake and Van der Waals interaction play key roles in mitochondrial toxicity. Theoretical equations have been used to explain the toxicity correlation, excess toxicity and QSAR for fish, cell and mitochondrial toxicity. Above results suggest that cytotoxicity can serve as a surrogate for fish toxicity and be used in the safety evaluation of organic pollutants in aqueous environment, but not mitochondrial toxicity, although some compounds share same modes of action between fish or cell toxicity and mitochondrial toxicity.

Immunomolecular response of CD4+, CD8+, TNF-α and IFN-γ in Myxobolus-infected koi (Cyprinus carpio) treated with probiotics

A poor environment increases fish's susceptibility to myxosporean infection that can cause the death of larval fish, especially for koi fish (Cyprinus carpio). This study aimed to determine the effect of probiotics, local anti-parasitic drugs (kutuklin), and the chemical compound diflubenzuron treatments on the koi immune response. This study used PCR with specific primer 18S SSU rDNA and DNA sequencing to detect Myxobulus phylogenetic. The treatments were divided into 5 groups: Treatment (A) (healthy koi without treatment), (B) (infected koi without treatment), (C) (infected koi with 0.55 mL/30 L probiotics), (D) (infected koi with 1 μL/g of feed kutuklin), and (E) (infected koi with 0.02 mg/5 L dimilin). Myxospore has observed with Scanning Electron Microscopy (SEM) and 4′,6-diamidino-2-phenylindole (DAPI) fluorescence staining. The histological analysis using semi-quantitative scoring methods, and flow cytometry was conducted to analyse the immune response of Cluster of differentiation 4 (CD4+), Cluster of differentiation 8 (CD8+), Tumor Necrosis Factor-alpha (TNF-α), Interferon gamma (IFN-γ) cells in the gills. Results show that the histological analysis indicated edema, hyperplasia, lamella fusion, congestion, and hypertrophy lesions in infected koi. Treatment with probiotics shows the lowest damage (30.6%). The immune responses of CD4+ and CD8+ cells to dimilin treatment were 10.54% and 16.86%, respectively. The largest TNF-α and IFN-γ response were for the kutuklin treatment (29.26%) and probiotics treatment (8.23%).

Evaluation of Histopathological Changes in Cantang Groupers’ Brain and Gill Infected with Streptococcus Iniae

Cantang hybrid grouper is the result of hybridization between female Macan grouper (Epinephelus fuscoguttatus) and male Kertang grouper (Epinephelus lanceolatus). Hybrid fish have better performance in terms of growth, resistance to diseases, and tolerance to environmental factors, compared to the parents. One of the diseases that can attack fish is an infection induced by Streptococcus iniae (S. iniae), which is quite a dangerous bacterium since it can cause mass death of fish. The present study aimed to investigate the pathological changes of the brain and gill of Cantang hybrid grouper (Epinephelus fuscoguttatus and Epinephelus lanceolatus) infected with S. iniae. A total of 180 groupers from the Management Unit of Brackish Water Aquaculture, Situbondo, Indonesia, were included in the current study with a length of 7 cm. The experimental study was conducted using a complete randomized design, including three treatments and three repetitions for each one (n = 20). The main parameters to observe the histopathological changes in the fish internal organs, namely the gill and the brain at the beginning and the end of the study. Moreover, the supporting parameter was the water quality which included the temperature, oxygen content, pH, and salinity. Several observations including the pathogenicity test, Lethal Dosage 50 test, observation of clinical symptoms, and observation of histopathology were done during the treatment. The obtained results were indicative of the histopathology damages in the brain and gill tissues of the Cantag hybrid groupers infected with S. iniae. Different scores of lesions, infiltration, congestion, and degeneration were indicated in the brain tissue. Furthermore, the gill damages consisted of hyperemia, congestion, and infiltration. In conclusion, Cantang hybrid groupers (Epinephelus fuscoguttatus and Epinephelus lanceolatus) infected with S. iniae indicated the clinical symptoms, anatomical pathology, and histopathological changes.

Generation of Reactive Oxygen Species (ROS) by Harmful Algal Bloom (HAB)-Forming Phytoplankton and Their Potential Impact on Surrounding Living Organisms.

Most marine phytoplankton with relatively high ROS generation rates are categorized as harmful algal bloom (HAB)-forming species, among which Chattonella genera is the highest ROS-producing phytoplankton. In this review, we examined marine microalgae with ROS-producing activities, with focus on Chattonella genera. Several studies suggest that Chattonella produces superoxide via the activities of an enzyme similar to NADPH oxidase located on glycocalyx, a cell surface structure, while hydrogen peroxide is generated inside the cell by different pathways. Additionally, hydroxyl radical has been detected in Chattonella cell suspension. By the physical stimulation, such as passing through between the gill lamellas of fish, the glycocalyx is easily discharged from the flagellate cells and attached on the gill surface, where ROS are continuously produced, which might cause gill tissue damage and fish death. Comparative studies using several strains of Chattonella showed that ROS production rate and ichthyotoxicity of Chattonella is well correlated. Furthermore, significant levels of ROS have been reported in other raphidophytes and dinoflagellates, such as Cochlodinium polykrikoides and Karenia mikimotoi. Chattonella is the most extensively studied phytoplankton in terms of ROS production and its biological functions. Therefore, this review examined the potential ecophysiological roles of extracellular ROS production by marine microalgae in aquatic environment.

ISOLATION OF STRAINS ANTAGONISTIC TO PATHOGENIC AEROMONADS FROM NATURAL POPULATIONS OF FISH AND BOTTOM SEDIMENTS

Increasing production efficiency and ensuring the environmental safety of commercial fish farming facilities through the creation of modern preparations for the treatment and prevention of diseases is a topical area of aquaculture. The study of the current situation shows that the factors limiting the possibilities of sustainable entry to the market, providing fish farms with high-quality highly productive breeding material and increasing the volume of commercial fish farming products are diseases of the breeding facilities. The development of new highly effective probiotic preparations for the prevention and treatment of aquaculture facilities will not only reduce the economic costs associated with the death of breeded fish, but will also help to increase the viability of fish, the accumulation of nutrients in tissues, and the correction of the microbiocenosis of the aquatic environment. The aim of the study is to search for natural Bacillus antagonistic strains promising for creating probiotics. The strains were isolated from bottom sediments and cyprinids of natural populations. In the course of the work, the antimicrobial spectrum of action of bacilli against the causative agents of aeromonosis, furunculosis and bacterial hemorrhagic septicemia (BHS) was studied. Aeromonas test-strains were isolated from sterlet, sturgeon, stellate sturgeon, trout, carp, grass carp, silver carp, grown in conditions of pond farms.

Cyanobacterial Blooms and Their Implications in the Changing Environment

Cyanobacteria are the most ancient phytoplankton that first appeared at least 2.5 billion years ago and have a prolonged evolutionary history. They can form impenetrable and toxic blooms in aquatic ecosystems such as freshwater and marine environments. Cyanobacterial blooms produce cyanotoxins that endanger ecosystem functioning and deteriorate water quality used for recreation, drinking, and in fisheries, thus, adversely affecting human health and the economy. Some bloom-producing genera are Aphanizomenon, Planktothrix, Cylindrospermopsis, Nodularia, Trichodesmium, Dolichospermum, and Microcystis. They increase turbidity and suppress submerged aquatic vegetation. Due to the microbial bloom-mediated environmental degradation, oxygen scarcity might occur, inducing hypoxia and anoxia, and resulting in the death of fish and benthic invertebrates. Several cyanotoxins cause many diseases related to digestion, liver, and neurological disorders when ingested by birds and mammals, including humans. Global changes resulting from human impacts like eutrophication, rising CO2 levels, and global warming are major driving forces for the enhancement of cyanobacterial blooms in many aquatic systems worldwide. Various management strategies such as nutrient load reduction, hydrodynamic changes, and chemical and biological controls have been used to reduce bloom occurrence and proliferation of cyanobacteria. In this chapter, we have discussed the approaches regarding the understanding of how global changes affect cyanobacterial blooms and also suggested effective prediction and management strategies.

Evaluation of Pollution Status and Detection of the Reason for the Death of Fish in Chamo Lake, Ethiopia.

Chamo Lake is the third largest rift valley lake and one of the major economic sources for the communities in the Southern region, Ethiopia. The lake's quality is deteriorating due to the untreated wastewater, and sediment inflow resulting in the death of fish was observed during the dry season. The research aims to determine the water quality status using water quality indices, in addition to identifying the reason for the death of fish in the dry season in Chamo Lake. The water samples were drawn from 5 sampling points by composite sampling method during the dry and wet seasons of the year, and we analyzed 22 water quality parameters. Ammonia (14–23.6 mg/l), phosphates (0.30–1.10 mg/l), BOD (25.32–60 mg/l), COD (40–160 mg/l), and chlorophyll (19.64–31.87 μg/L) concentrations were above the permissible limits, and DO (5.20–6.70 mg/l) was below the acceptable limit in the lake as per EPA standards concerning temperature. The values of both the water quality indices of CCMEWQI (13.90–18.40) and NSFWQI (38.59–49.63) indicated that the water quality was “poor” and “bad,” respectively. The death of fish might be due to high concentrations of ammonia and nutrients in the dry season.

Sublethal toxicity effects of glyphosate and propanil on some haematological parameters in juveniles of freshwater catfish, Clarias gariepinus (Teugels, 1986)

The use of agrochemicals in developing countries for the eradication of different pests/weeds has been on the increasing trend. This might be due to increasing human population, intensive agriculture, industrialization and urbanization. However, the objective of this work is to study the sub-lethal toxicity effects of glyphosate and propanil on some haematological changes in the freshwater fish Clarias gariepinus juveniles. The experiment was conducted in the laboratory for a period of 56 days. Juveniles fish of Clarias gariepinus of mixed sexs, males and females were randomly exposed to sub lethal concentrations of the two herbicides, 0.11, 0.14, 0.21 mg/L and control (0.00 mg/L) for glyphosate and 0.23, 0.31, 0.46 mg/L and control (0.00 mg/L) for propanil respectively. However, blood samples were collected for the determination of some haematological changes after 56 days. Assessment of haematological parameters revealed significant decreases in RBCC, HB and PCV. In contrast, a highly significant (p≤0.05) dose and duration dependent elevation was recorded in WBCC and MCH in all experimental groups compared with control exposures. There was also increased in lymphocytes and decreased in neutrophils counts in glyphosate and propanil exposure of C. gariepinus juveniles. The study has shown that the exposure of the fish C. gariepinus juveniles to the herbicides glyphosate and propanil can lead to alterations in the haematological parameters of both stages of the fish which could inflicts unfavourable physiological changes in the target organism, therefore leading to death of fish. Howerver, there is the need to protect fish with a view to sustaining our rich biodiversity in Nigerian. The study therefore, revealed that exposing C. gariepinus juveniles to sublethal concentrations of glyphosate and propanil causes an upset on the haematological parameters and implies poor environmental fitness for fish exposed to herbicides in natural environments.

Parasitic Protozoa found in the skin, gills, and intestines of Patin Catfish (Pangasius hypophthalmus) and Common Carp (Cyprinus carpio)

The parasitic protozoa found in "Ikan Patin" or a species of Catfish (Pangasius hypophthalmus) and "Ikan Mas" or Common Carp (Cyprinus carpio) are Trichodina sp., Ichthyophthirius sp. and Myxobolus sp. These protozoa have the potential to cause death in fish and economic losses to fish farmers and sellers. This study was conducted to determine the presence of parasitic protozoa on the skin, gills, and intestines of Catfish and Carp. Samples were taken from the Bursa Ikan Hias Laladon or Laladon Ornamental Fish Market in Bogor, Indonesia. Each species was sampled for as many as 30 fish. The skin, gills, and intestines were examined using the native examination method and Lugol staining. Parasitic protozoa were identified based on their morphology, namely size, and shape. The types of parasitic protozoa found on the skin, gills, and intestines of Catfish and goldfish were Trichodina sp., Ichthyophthirius sp., and Myxobolus sp. The parasites were found in skin organs in as many as 29 samples (96.7%) from Catfish and 30 samples (100%) from Carp. The Genera of Ichthyophthirius sp. were found in the gills of 2 samples (6.7%) in Catfish and 1 sample (3.3%) from positive Carp. Myxobolus sp. was found in the intestines of 11 samples (36.7%) from Catfish and two samples (6.7%) from Carp. The species of Trichodina sp. found based on morphology was Trichodina giurusi.©2021 JNSMR UIN Walisongo. All rights reserved.

Assessment of ecological conditions for growing the market-size fish in the Kantivka fattening pond (Khmelnychchyna, Ukraine)

Abiotic (water quality) and biotic (Phyto-, zooplankton and benthos) factors in the Kantivka fattening pond the Khmelnitskrybhosp Private Joint-Stock Company were studied during the vegetation seasons in 2020. The aquaculture objects in the pond are cyprinid fish species (carp, grass carp, silver carp, pike). The ecological conditions of the pond were evaluated as good enough for the fish fattening purpose. The critical water quality parameters were following traditional values accepted for fish farming in Ukraine. The taxonomic composition of plankton and benthos was represented by widespread and Ubiquiti species mainly. The 124 species and intraspecies taxa of microalgae and the 34 species of zooplankton were identified in the Kantivka fattening pond. The mean abundance and biomass for the phytoplankton were 183.8 million cells/dm3 and 35.61 mg/dm3, respectively; for zooplankton, those were as 336600 ind/m3 and 14.83 g/m3, and for zoobenthos, those values were as 309.6 ind/m2, and biomass as 5.84 g/m2. Such parameters of natural forage base correspond to the optimal values for natural fish food according to fish farming standards in Ukraine. In the late summer, the free-living copepod stages and mature adult females of the parasitic copepod crustacean Ergasilus sieboldi Nordmann were registered in plankton. This copepod causes the invasion of fish diseases like infection and destruction of gill arches, which leads to a severe disturbance in fish respiration, emaciation, delaying in growth, and the potential death of commercial fish even. The development of natural fish food in the Kantivka fattening pond is shown an intensive level of biomass and abundance of phytoplankton, zooplankton, and zoobenthos. It is considered sufficient to meet the natural nutritional needs (in combination with artificial feeding) for older age groups of the cultivated cyprinid fish species.

Dietary Glutamine Inclusion Regulates Immune and Antioxidant System, as Well as Programmed Cell Death in Fish to Protect against Flavobacterium columnare Infection.

The susceptibility of animals to pathogenic infection is significantly affected by nutritional status. The present study took yellow catfish (Pelteobagrus fulvidraco) as a model to test the hypothesis that the protective roles of glutamine during bacterial infection are largely related to its regulation on the immune and antioxidant system, apoptosis and autophagy. Dietary glutamine supplementation significantly improved fish growth performance and feed utilization. After a challenge with Flavobacterium columnare, glutamine supplementation promoted il-8 and il-1β expression via NF-κB signaling in the head kidney and spleen, but inhibited the over-inflammation in the gut and gills. Additionally, dietary glutamine inclusion also enhanced the systematic antioxidant capacity. Histological analysis showed the protective role of glutamine in gill structures. Further study indicated that glutamine alleviated apoptosis during bacterial infection, along with the reduced protein levels of caspase-3 and the reduced expression of apoptosis-related genes. Moreover, glutamine also showed an inhibitory role in autophagy which was due to the increased activation of the mTOR signaling pathway. Thus, our study for the first time illustrated the regulatory roles of glutamine in the fish immune and antioxidant system, and reported its inhibitory effects on fish apoptosis and autophagy during bacterial infection.

Risk of Climate Variability on Tilapia Cage Culture in Songkhram River in Northeastern Thailand

The cage culture of Nile Tilapia in the river is one of the most important methods for Nile Tilapia (Oreochromis niloticus) farming in Thailand. Songkhram river is a significant river in north-eastern Thailand where Nile Tilapia river-based cage culture has been applied widely. However, river-based cage culture is an open culturing system where farmers do not fully control weather and water quality. This study investigates the risks of climate variability on Nile Tilapia in riv-er-based cage culture. This study recommends strategies to reduce fish yield losses. The samples of this study are the Nile Tilapia river-based cage culture farmers along the Songkhram river in 5 districts in Sakon Nakhon and Nakhon Phanom, including Thauthen, Khamtakla, Akatamnuai, Sisongkhram and Nathom. This study applies a simple random sampling method. We used structured questionnaires to collect the data from 148 fish farmers between April and December 2017. Hot weather during March and April was perceived to be the most important factor causing fish diseases and led to losses (68.2 %). The other significant factors that led to fish death were drought (52.7 %) and flood (40.5 %). Flood typically takes place between June and August. Cold weather was perceived not to affect the fish losses (32.4 %). However, it did affect the growth rate. Cold weather typically takes place between December and February. Re-garding the hot weather, fish farmers applied preventive measures such as mon-itoring and surveillance, stopping or delaying stocking schedules. For drought, the fish farmers relocated the cages towards the deeper water areas and used aerators to control water quality. Most farmers tie their cages securely during flooding season and relocate them closer to the bank. The fish farmers moni-tored their cages more closely than usual for the cold weather and postponed the stocking date. The study of risks and loss mitigation from climate variabilities in this research will be helpful for strategic aquaculture planning to cope with cli-mate variabilities in the future.

Smart Fish Farm based on IoT As Monitoring to Reduce the Number of Death in Guppy Fish

During the transition from dry season to rainy season or vice versa, very high temperature fluctuations often occur, causing large number of deaths in guppy fish farming. The death of this guppy fish is also triggered by water conditions that are not maintained. Therefore, a system that can monitor water conditions in real time without being limited by distance, and that can cope the drastic temperature changes is needed. If water conditions can be monitored in real time, of course, the guppy fish in aquarium or tank will become healthier, well-maintained and will produce the best quality guppy fish. For this reason, the researcher makes a system that is able to monitor the condition of water in the aquarium to reduce the number of deaths in guppies. The researcher conducts trials using Fuzzy Mamdani method of three input variables from water temperature sensor, pH sensor and turbidity sensor which defuzzification result shows crips output value at 44.63. That result puts water condition in “Fair” level, and when it is matched with the calculation result of matlab r2013a using Fuzzy Mamdani, the result is 44.8 which is not far different. The result of this study is a smart fish farm system that can monitor water conditions in aquariums or tanks, such as: feeding time, checking and controlling temperature, monitoring water pH, monitoring water turbidity levels, lights control that can automatically turn on and off with room lighting indicators, and drain when the water is turbid. This smart fish farm system is made with an Arduino microcontroller that is connected to the internet based on Internet of Things (IoT) and the Mamdani Fuzzy Logic method. This smart fish farm system can also store records with platforms from Thingspeak and MitApp for the mobile applications making.

Acute toxicity of eucalyptus leachate tannins to zebrafish and the mitigation effect of Fe3+ on tannin toxicity

Fish ponds polluted by the black water of eucalyptus forests (formed by the complexation of eucalyptus tannins with Fe3+) have experienced fish deaths. However, the toxicity of the components of black water is still unclear. To study the acute toxicities of eucalyptus leachate tannins to fish, their changes in the presence of Fe3+, and the underlying mechanisms, the static bioassay test method was adopted for acute exposure testing of zebrafish. Zebrafish were exposed to three kinds of tannins, namely, tannic acid (TA), epigallocatechin gallate (EGCG) and tannins from fresh eucalyptus leaf leacheate (TFL), and to solutions of these tannins with different molar ratios of Fe3+, under both no-aeration and aeration conditions. The results showed that the 48 h LC50 values of TA, EGCG and TFL were respectively 92, 47, and 186 mg·L−1, under no aeration, and 171, 86, and 452 mg·L−1 under aeration. When Fe3+ at 2, 1, and 6 times the molar amount of tannin was added to LC100 solutions of TA, EGCG and TFL, zebrafish mortality in 24 h was reduced to 0–33%. Acute fish death in eucalyptus plantation areas is related to high concentrations of eucalyptus tannins in the water. However, with increasing dissolved oxygen and Fe3+ levels, the acute toxicity of tannins to fish can be reduced. Thus, the black water in eucalyptus plantation areas reflects a water quality phenomenon that reduces the acute toxicity of eucalyptus tannins to fish. The mechanism of tannin toxicity to fish may be related to the impairment of oxygen delivery by fish blood, but the mechanism needs further study. These results provide a scientific basis for the prevention and control of fish suffering from acute eucalyptus tannin poisoning in eucalyptus plantation areas and for the protection of water resources.

Effects of variation of holding temperature on physiological and biochemical parameters of juvenile sturgeon fish in the conditions of industrial breeding

Below are presented the results of physiological stress (sudden temperature variations) affecting the physiological and biochemical parameters of juvenile sturgeon fish (sterlet and Siberian sturgeon) in the conditions of industrial breeding. They show that the temperature variations in the range of ±15 °С at the rate of 5 °С/hour towards temperature decrease are reversible physiological stress for physiologically healthy starving juvenile sturgeons, with which the species cope well if corresponding adaptation mechanisms are used (100 % survival rate). According to the examined physiological and biochemical parameters, the temperature variation towards decrease has its impact on the respiratory frequency (if the temperature decreases by 5 °С during the first hour of exposure, it increases by 30 % from the initial frequency; in three hours of exposure it decreases by 15 % from the initial frequency if the temperature decreases by 15 °С) and blood glucose level which increases by 15, 30 and 50 % every hour of exposure. The same temperature variations towards increase lead to irreversible physiological changes accompanied by the manifestations of acute stress reaction and death of juvenile fish depending on the severity and duration of temperature stress. During the first hour of exposure, the respiratory frequency increases twice, during the second hour it increases 2.5-fold, and 3-fold during the third hour. Blood glucose level increases by 10% during the first hour, twice during the second hour, 3-fold during the third hour from the initial level. Blood lactate level increases 5-fold from the initial level between the second and the third hour of exposure. Acute stress reaction beyond the adaptive capabilities manifests itself as a drop in fish survival rate in the second or the third hour of temperature increase, from 80-90% to 0% of general fish quantity in the experiment respectively.

The application of baffle block in mitigating TDGS of dams with different discharge patterns

Total dissolved gas supersaturation (TDGS) caused by high-dam discharge leads to gas-bubble trauma or even death in fish and has become an active research area because of global concern regarding this issue. It is important to use engineering measures to reduce the TDGS level to protect the fish habitat and water environment. As there are different mechanisms for TDGS generation by discharge, the application of mitigation measures needs to be investigated. In this study, three dams in which bottom flow, surface flow and trajectory jet used for energy dissipation were simulated to analyze the characteristics of TDGS generation and distribution. The simulated results show that the generation and distribution of TDGS is affected by bubble-water mass transfer. Consequently, a mitigation measure in which baffle blocks installed downstream of the spillway was proposed to change transport bubbles to low-pressure regions. The simulated results showed this engineering measure reduced TDGS by 5.2% and 13.1% for dams with bottom flow and trajectory jet, respectively. This study serves as a reference for the characteristics of TDGS generation and the design of TDGS mitigation measures.

The Resilience of Small-Scale Fishing Households to the Anthropogenic Environmental Shocks

The marine environmental incident causing mass fish death in Central Vietnam by Formosa Ha Tinh Steel Plant in 2016 severely impacted people's livelihoods in four provinces. Several previous studies have indicated that diversifying livelihoods is one of the best solutions to increase the resilience of households to overcome such incidents. This study investigated the relationship between livelihood diversification and the stability of small-scale fishing households. Our findings showed that impact levels and resilience capacity under family perception are important aspects for impact assessment in the context of the environmental shock. Local families can diversify their livelihoods based on their resources as well as through government-supporting policies. The livelihood diversification of impacted households is significantly valuable in increasing the resilience process after the Formosa incident. Families with more livelihood activities related to income sources have better resilience than families with less livelihood activities. By the effort of households and government support policies, impacted households have gradually improved their livelihood resilience.

Real-time detection and tracking of fish abnormal behavior based on improved YOLOV5 and SiamRPN++

In recirculating aquaculture system, the abnormal behavior of fish is usually caused by poor water quality, hypoxia or diseases. Delayed recognition of this behavior will lead to large number of fish deaths. Thus, real-time detection and tracking of fish that behaviors abnormally is an effective way to promote the fish welfare and to improve the survival rate as well as economic benefits of aquaculture. However, due to the high-density breeding, the targets in the fish images are often quite small and in occlusion, which causes high false detection and target loss rate. This article proposes a combined end-to-end neural network to detect and track the abnormal behavior of porphyry seabream. The detection algorithm passes the initial value of the target into the tracking algorithm, and the tracking algorithm tracks subsequent frames to achieve end-to-end abnormal fish behavior detection and achieve high-speed and accurate tracking of abnormal behavior individuals.In the target detection part, YOLOV5s is improved by incorporating multi-level features and adding feature mapping. Compared with the original network, the detection precision AP50:95 is increased by 8.8% while AP50 reaches 99.4%. In the target tracking part, this paper achieves multi-target tracking of abnormal fish based on single-target tracking algorithm SiamRPN++. The tracking precision is 76.7%. By combining the two approaches, individual fish with abnormal behavior can be detected precisely and tracked in real time.