Connecting thiamine availability to the microbial community composition in Chinook salmon spawning habitats of the Sacramento River basin.

Thiamine deficiency complex (TDC) is a major emerging threat to global populations of culturally and economically important populations of salmonids. Salmonid eggs and embryos can assimilate exogenous thiamine, and evidence suggests that microbial communities in benthic environments can produce substantial amounts of thiamine. We therefore hypothesize that natural dissolved pools of thiamine exist in the surface water and hyporheic zones of riverine habitats where salmonids with TDC migrate, spawn, and begin their lives. To examine the relationship between dissolved thiamine-related compounds (dTRCs) and their microbial source, we determined the concentrations of these metabolites and the compositions of microbial communities in surface and hyporheic waters of the Sacramento River, California and its tributaries. Here we determine that all dTRCs are present in femto-picomolar concentrations in a range of critically important salmon spawning habitats. We observed that thiamine concentrations in the Sacramento River system are orders of magnitude lower than those of marine waters, indicating substantial differences in thiamine cycling between these two environments. Our data suggest that the hyporheic zone is likely the source of thiamine to the overlying surface water. Temporal variations in dTRC concentrations were observed where the highest concentrations existed when Chinook salmon were actively spawning. Significant correlations were seen between the richness of microbial taxa and dTRC concentrations, particularly in the hyporheic zone, which would influence the conditions where embryonic salmon incubate. Together, these results indicate a connection between microbial communities in freshwater habitats and the availability of thiamine to spawning TDC-impacted California Central Valley Chinook salmon.IMPORTANCEPacific salmon are keystone species with considerable economic importance and immeasurable cultural significance to Pacific Northwest indigenous peoples. Thiamine deficiency complex has recently been diagnosed as an emerging threat to the health and stability of multiple populations of salmonids ranging from California to Alaska. Microbial biosynthesis is the major source of thiamine in marine and aquatic environments. Despite this importance, the concentrations of thiamine and the identities of the microbial communities that cycle it are largely unknown. Here we investigate microbial communities and their relationship to thiamine in Chinook salmon spawning habitats in California's Sacramento River system to gain an understanding of how thiamine availability impacts salmonids suffering from thiamine deficiency complex.

Novel protective aspects of dietary polyphenols against pesticidal toxicity and its prospective application in rice-fish mode: A Review.

The rice fish system represents an innovative and sustainable approach to integrated farming, combining rice cultivation with fish rearing in the same ecosystem. However, one of the major challenges in this system is the pesticidal pollution resulting from various sources, which poses risks to fish health and overall ecosystem balance. In recent years, dietary polyphenols have emerged as promising bioactive compounds with potential chemo-preventive and therapeutic properties. These polyphenols, derived from various plant sources, have shown great potential in reducing the toxicity of pesticides and improving the health of fish within the rice fish system. This review aims to explore the novel aspects of using dietary polyphenols to mitigate pesticidal toxicity and enhance fish health in the rice fish system. It provides comprehensive insights into the mechanisms of action of dietary polyphenols and their beneficial effects on fish health, including antioxidant, anti-inflammatory, and detoxification properties. Furthermore, the review discusses the potential application methods of dietary polyphenols, such as direct supplementation in fish diets or through incorporation into the rice fields. By understanding the interplay between dietary polyphenols and pesticides in the rice fish system, researchers can develop innovative and sustainable strategies to promote fish health, minimize pesticide impacts, and ensure the long-term viability of this integrated farming approach. The information presented in this review will be valuable for scientists, aqua-culturists, and policymakers aiming to implement eco-friendly and health-enhancing practices in the rice fish system.

Immunological and molecular diagnostic techniques in fish health: present and future prospectus.

Fish health management is critical to aquaculture and fisheries as it directly affects sustainability and productivity. Fish disease diagnosis has taken a massive stride because of advances in immunological and molecular diagnostic tools which provide a sensitive, quick, and accurate means of identifying diseases. This review presents an overview of the main molecular and immunological diagnostic methods for determining the health of fish. The immunological techniques help to diagnose different fish diseases by detecting specific antigens and antibodies. The application of immunological techniques to vaccine development is also examined in this review. The genetic identification of pathogens is made possible by molecular diagnostic techniques that enable the precise identification of bacterial, viral, and parasitic organisms in addition to evaluating host reactions and genetic variation associated with resistance to disease. The combination of molecular and immunological methods has resulted in the creation of novel techniques for thorough evaluation of fish health. These developments improve treatment measures, pathogen identification and provide new information about the variables affecting fish health, such as genetic predispositions and environmental stresses. In the framework of sustainable fish farming and fisheries management, this paper focuses on the importance of these diagnostic techniques that play a crucial role in protecting fish populations and the aquatic habitats. This review also examines the present and potential future directions in immunological and molecular diagnostic techniques in fish health.

Poison in the water: Arsenic's silent assault on fish health.

Arsenic occurs across the world in freshwater and marine environments, menacing the survival of aquatic organisms. Organic and inorganic forms of this substance can be found, in which the inorganic form is more hazardous than the organic form. Most aquatic bodies contain inorganic arsenic species, but organic species are believed to be the dominant form of arsenic in the majority of fish. Natural and anthropogenic both are the sources of water contamination with arsenic. Its bioaccumulation and transfer from one trophic level to another in the aquatic food chain make arsenic a vital environmental issue. Continuous exposure to low concentrations of arsenic in aquatic organisms including fish leads to its bioaccumulation, which may affect organisms of higher trophic levels including large fishes or humans. Humans can be exposed to arsenic through the consumption of fish contaminated with arsenic. Hence, the present review facilitates our understanding about sources of arsenic, its bioaccumulation, food chain transfer, and its effect on the fish health. Also, "Poison in the Water: Arsenic's Silent Assault on Fish Health" serves as a wake-up call to recognize the pressing need to address arsenic contamination in water bodies. By understanding its devastating impact on fish health, we can strive to implement sustainable practices and policies that safeguard our precious aquatic environments and ensure the well-being of both wildlife and human communities that depend on them.

Acipenserid herpesvirus 2 genome and partial validation of a qPCR for its detection in white sturgeon Acipenser transmontanus.

White sturgeon Acipenser transmontanus is the primary species used for caviar and sturgeon meat production in the USA. An important pathogen of white sturgeon is acipenserid herpesvirus 2 (AciHV-2). In this study, 4 archived isolates from temporally discrete natural outbreaks spanning the past 30 yr were sequenced via Illumina and Oxford Nanopore Technologies platforms. Assemblies of approximately 134 kb were obtained for each isolate, and the putative ATPase subunit of the terminase gene was selected as a potential quantitative PCR (qPCR) target based on sequence conservation among AciHV-2 isolates and low sequence homology with other important viral pathogens. The qPCR was repeatable and reproducible, with a linear dynamic range covering 5 orders of magnitude, an efficiency of approximately 96%, an R2 of 0.9872, and an analytical sensitivity of 103 copies per reaction after 35 cycles. There was no cross-reaction with other known viruses or closely related sturgeon species, and no inhibition by sturgeon DNA. Clinical accuracy was assessed from white sturgeon juveniles exposed to AciHV-2 by immersion. Viral culture (gold standard) and qPCR were in complete agreement for both cell culture negative and cell culture positive samples, indicating that this assay has 100% relative accuracy compared to cell culture during an active outbreak. The availability of a whole-genome sequence for AciHV-2 and a highly specific and sensitive qPCR assay for detection of AciHV-2 in white sturgeon lays a foundation for further studies on host-pathogen interactions while providing a specific and rapid test for AciHV-2 in captive and wild populations.

Changes in blood serum parameters in farmed rainbow trout (Oncorhynchus mykiss) during a piscine lactococcosis outbreak.

The aquaculture sector plays a vital role in global food security, yet it grapples with significant challenges posed by infectious diseases. Piscine lactococcosis is one of the significant threats in rainbow trout aquaculture due to its potential to cause severe economic losses through mortalities, reduced growth rates, and increased susceptibility to other pathogens. It poses challenges in disease management strategies, impacting the sustainability and profitability of rainbow trout farming. The current study focuses on the variations in serum blood parameters of farmed rainbow trout Oncorhynchus mykiss during a lactococcosis outbreak caused by Lactococcus garvieae. Blood samples were collected for biochemical analysis, fish were examined for parasites and bacteria, and DNA from bacterial colonies was PCR-amplified and sequenced for identification. Overall, 13 biochemical parameters, including proteins, enzymes, lipids, chemicals, and minerals, were measured in serum blood samples from both diseased and healthy fish. The results indicate significant alterations in the levels of these parameters during the outbreak, highlighting the impact of infections on the blood profile of farmed rainbow trout. Urea levels were significantly higher in diseased fish compared to controls, and creatinine, phosphorus, and magnesium also showed similar trends. Alanine aminotransferase and total protein levels were higher in control fish. Chloride levels differed significantly between groups. Iron levels were higher in controls and lower in diseased fish. No significant differences were found in other parameters. This study reveals significant changes in serum blood parameters of rainbow trout during a lactococcosis outbreak caused by L. garvieae. These changes highlight the potential of these parameters as tools for monitoring health status, stress, and aquaculture management. Continuous monitoring can provide valuable insights into disease severity and overall fish health, aiding in the development of improved management practices. The presented data contribute to understanding the pathophysiology of piscine lactococcosis and developing effective mitigation strategies for farmed rainbow trout.

Diploid and triploid Chinook salmon (Oncorhynchus tshawytscha) exhibit differential immunological responses to acute thermal stress.

Exposure to temperatures outside of a fish's optimal range results in suppression of the immune system, ultimately leaving aquaculture stocks susceptible to disease outbreaks. This effect is exacerbated in triploid fishes, which demonstrate greater susceptibility to stress than their diploid counterparts. This study investigates the impacts of acute heat stress on the abundance of immune transcripts and proteins in diploid and triploid Chinook salmon (Oncorhynchus tshawytscha), an important finfish crop. This study also demonstrates that acute heat stress induces significant increases in the abundance hsp70, hsp90 and il1b transcripts in the head kidneys, gills and heart ventricles of both diploid and triploid Chinook salmon. Widespread dysregulation of antigen-presentation transcripts was also observed in fish of both ploidies. These results suggest that acute heat stress activates acute-phase responses in Chinook salmon and dysregulates antigen presentation, potentially leaving fish more susceptible to infection. At the protein level, IL-1ß was differentially expressed in the head kidney and ventricles of diploid and triploid salmon following heat shock. Differential expression of two tapasin-like proteins in diploid and triploid salmon subjected to heat shock was also observed. Altogether, these data indicate that diploid and triploid Chinook salmon respond differently to acute thermal stressors.

Replacement of fishmeal with a microbial single-cell protein induced enteropathy and poor growth outcomes in barramundi (Lates calcarifer) fry.

Fish meal (FM) replacement is essential for the sustainable expansion of aquaculture. This study focussed on the feasibility of replacing FM with a single-cell protein (SCP) derived from methanotrophic bacteria (Methylococcus capsulatus, Bath) in barramundi fry (Lates calcarifer). Three isonitrogenous and isoenergetic diets were formulated with 0%, 6.4% and 12.9% inclusion of the SCP, replacing FM by 0%, 25% and 50%. Barramundi fry (initial body weight 2.5 ± 0.1 g) were fed experimental diets for 21 days to assess growth performance, gut microbiome composition and gut histopathology. Our findings revealed that both levels of SCP inclusion induced detrimental effects in barramundi fry, including impaired growth and reduced survival compared with the control group (66.7% and 71.7% survival in diets replacing FM with SCP by 25% and 50%, respectively; p < .05). Both dietary treatments presented mild necrotizing enteritis with subepithelial oedema and accumulation of PAS positive, diastase resistant droplets within hepatocytes (ceroid hepatopathy) and pancreatic atrophy. Microbiome analysis revealed a marked shift in the gut microbial community with the expansion of potential opportunistic bacteria in the genus Aeromonas. Reduced overall performance in the highest inclusion level (50% SCP) was primarily associated with reduced feed intake, likely related to palatability issues, albeit pathological changes observed in gut and liver may also play a role. Our study highlights the importance of meticulous optimization of SCP inclusion levels in aquafeed formulations, and the need for species and life-stage specific assessments to ensure the health and welfare of fish in sustainable aquaculture practices.

Mucosal organs exhibit distinct response signatures to hydrogen sulphide in Atlantic salmon (Salmo salar).

Hydrogen sulphide (H2S) is considered an immunotoxicant, and its presence in the water can influence the mucosal barrier functions of fish. However, there is a significant knowledge gap on how fish mucosa responds to low environmental H2S levels. The present study investigated the consequences of prolonged exposure to sub-lethal levels of H2S on the mucosal defences of Atlantic salmon (Salmo salar). Fish were continuously exposed to two levels of H2S (low: 0.05 µM; and high: 0.12 µM) for 12 days. Unexposed fish served as control. Molecular and histological profiling focused on the changes in the skin, gills and olfactory rosette. In addition, metabolomics and proteomics were performed on the skin and gill mucus. The gene expression profile indicated that the gills and olfactory rosette were more sensitive to H2S than the skin. The olfactory rosette showed a dose-dependent response, but not the gills. Genes related to stress responses were triggered at mucosal sites by H2S. Moreover, H2S elicited strong inflammatory responses, particularly in the gills. All mucosal organs demonstrated the key molecular repertoire for sulphide detoxification, but their temporal and spatial expression was not substantially affected by sub-lethal H2S levels. Mucosal barrier integrity was not considerably affected by H2S. Mucus metabolomes of the skin and gills were unaffected, but a matrix-dependent response was identified. Comparing the high-concentration group's skin and gills mucus metabolomes identified altered amino acid biosynthesis and metabolism pathways. The skin and gill mucus exhibited distinct proteomic profiles. Enrichment analysis revealed that proteins related to immunity and metabolism were affected in both mucus matrices. The present study expands our knowledge of the defence mechanisms against H2S at mucosal sites in Atlantic salmon. The findings offer insights into the health and welfare consequences of sub-lethal H2S, which can be incorporated into the risk assessment protocols in salmon land-based farms.

Mucosal and systemic physiological changes underscore the welfare risks of environmental hydrogen sulphide in post-smolt Atlantic salmon (Salmo salar).

Atlantic salmon (Salmo salar) might encounter toxic hydrogen sulphide (H2S) gas during aquaculture production. Exposure to this gas can be acute or chronic, with heightened levels often linked to significant mortality rates. Despite its recognised toxicity, our understanding of the physiological implications of H2S on salmon remains limited. This report details the mucosal and systemic physiological consequences in post-smolt salmon reared in brackish water at 12 ppt after prolonged exposure to elevated H2S levels over 4 weeks. The fish were subjected to two concentrations of H2S: 1 µg/L (low group) and 5 µg/L (high group). An unexposed group at 0 µg/L served as the control. Both groups exposed to H2S exhibited incremental mortality, with cumulative mortality rates of 4.7 % and 16 % for the low and high groups, respectively. Production performance, including weight and condition factors, were reduced in the H2S-exposed groups, particularly in the high group. Mucosal response of the olfactory organ revealed higher tissue damage scores in the H2S-exposed groups, albeit only at week 4. The high group displayed pronounced features such as increased mucus cell density and oedema-like vacuoles. Transcriptome analysis of the olfactory organ unveiled that the effects of H2S were more prominent at week 4, with the high group experiencing a greater magnitude of change than the low group. Genes associated with the extracellular matrix were predominantly downregulated, while the upregulated genes primarily pertained to immune response. H2S-induced alterations in the metabolome were more substantial in plasma than skin mucus. Furthermore, the number of differentially affected circulating metabolites was higher in the low group compared to the high group. Five core pathways were significantly impacted by H2S regardless of concentration, including the phenylalanine, tyrosine, and tryptophan biosynthesis. The plasma levels of phenylalanine and tyrosine were reduced following exposure to H2S. While there was a discernible distinction in the skin mucus metabolomes among the three treatment groups, only one metabolite - 4-hydroxyproline - was significantly impacted by H2S. Furthermore, this metabolite was significantly reduced in the plasma and skin mucus of H2S-exposed fish. This study underscores that prolonged exposure to H2S, even at concentrations previously deemed sub-lethal, has discernible physiological implications that manifest across various organisational levels. Given these findings, prolonged exposure to H2S poses a welfare risk, and thus, its presence must be maintained at low levels (<1 µg/L) in salmon land-based rearing systems.

Enhancing immune and antioxidant responses in Nile tilapia through dietary supplementation with Ulva fasciata extract: A study on gene expression and resistance to Aeromonas hydrophila.

BACKGROUND: The study focused on the impact of Ulva fasciata extract (UFE) supplementation in the diets of Nile tilapia (Oreochromis niloticus) on blood and biochemical markers, immune and oxidative responses, and the expression of related genes, with a specific interest in their condition following exposure to Aeromonas hydrophila. METHODS: Four different levels of UFE were tested in the diets: 0% (0 mg kg- 1) for the control group (U0), and incremental additions of 0.05% (50 mg kg-1), 0.1% (100 mg kg-1), and 0.15% (150 mg kg-1) for the experimental groups U50, U100, and U150 respectively. Groups of 45 fish weighing 3.126 ± 0.120 g were fed these diets over 90 days. RESULTS: The study found that groups treated with UFE showed statistically significant enhancements (p < 0.05) compared to the control group. These improvements included increased red and white blood cell counts, higher haemoglobin concentrations, greater packed cell volume, and elevated enzyme activities-specifically, superoxide dismutase, catalase, alanine aminotransferase, and aspartate aminotransferase. Additionally, lysozyme and phagocytic activities were notably higher, especially in the U100 group after exposure. Before exposure to Aeromonas hydrophila, all levels of UFE supplementation led to increased expression of TNF-α and COXII genes and decreased NFκ-B expression. After the challenge, UFE intake resulted in varied expression levels of immune and antioxidant genes (TNF-α, NFκ-B, SOD, and COXII) in the liver, with the most effective responses observed in the U50, U100, and U150 groups. CONCLUSIONS: The findings underscore the potential of dietary UFE as a natural antioxidant and immune booster for Nile tilapia.

In-depth health surveillance and clinical nutrition in farmed Atlantic salmon: a strategic attempt to detect and mitigate an HSMI outbreak.

Fish health personnel have limited tools in combatting viral diseases such as heart and skeletal muscle inflammation (HSMI) in open net-pen farmed Atlantic salmon. In this study, we aimed to predict HSMI by intensified health monitoring and apply clinical nutrition to mitigate the condition. We followed a commercial cohort (G1) of Atlantic salmon that was PRV-1 naïve when transferred to a sea cage at a location where HSMI outbreaks commonly occur. The fish in the other cages (G2-G6) at the location had a different origin than G1 and were PRV-1 positive prior to sea transfer. By continuous analysis of production data and sequentially (approximately every fourth week) performing autopsy, RT-qPCR (for PRV-1 and selected immune genes), blood and histological analysis of 10 fish from G1 and G2, we identified the time of PRV-1 infection in G1 and predicted the onset of HSMI prior to any clinical signs of disease. Identical sequences across partial genomes of PRV-1 isolates from G1 and G2 suggest the likely transfer from infected cages to G1. The isolates were grouped into a genogroup known to be of high virulence. A commercial health diet was applied during the HSMI outbreak, and the fish had low mortality and an unaffected appetite. In conclusion, we show that fish health and welfare can benefit from in-depth health monitoring. We also discuss the potential health value of clinical nutrition as a mean to mitigate HSMI.

Purification and concentration of infectious koi herpesvirus using steric exclusion chromatography.

Koi herpesvirus (KHV) is the causative agent of a koi herpesvirus disease (KHVD) inducing high mortality rates in common carp and koi (Cyprinus carpio). No widespread effective vaccination strategy has been implemented yet, which is partly due to side effects of the immunized fish. In this study, we present an evaluation of the purification of infectious KHV from host cell protein and DNA, using the steric exclusion chromatography. The method is related to conventional polyethylene glycol (PEG) precipitation implemented in a chromatographic set-up and has been applied for infectious virus particle purification with high recoveries and impurity removal. Here, we achieved a yield of up to 55% of infectious KHV by using 12% PEG (molecular weight of 6 kDa) at pH 7.0. The recoveries were higher when using chromatographic cellulose membranes with 3-5 µm pores in diameter instead of 1 µm. The losses were assumed to originate from dense KHV precipitates retained on the membranes. Additionally, the use of >0.6 M NaCl was shown to inactivate infectious KHV. In summary, we propose a first step towards a purification procedure for infectious KHV with a possible implementation in fish vaccine manufacturing.

Improving the diagnosis of Streptococcus iniae using a novel probe-based qPCR assay combined with an enrichment step.

Streptococcus iniae is a bacterial pathogen that causes streptococcosis, leading to significant losses in fish aquaculture globally. This study reported a newly developed probe-based quantitative polymerase chain reaction (qPCR) method for the detection of S. iniae. The primers and probes were designed to target the lactate oxidase gene. The optimized method demonstrated a detection limit of 20 copies per reaction and was specific to S. iniae, as evidenced by no cross-reactivity when assayed against genetic materials extracted from 23 known aquatic animal pathogens, and fish samples infected with Streptococcus agalactiae or Streptococcus dysgalactiae. To validate the newly developed qPCR protocol with field samples, fish specimens were systematically investigated following the Food and Agriculture Organization of the United Nations & Network of Aquaculture Centres in Asia-Pacific three diagnostic levels approach, which integrated basic and advanced techniques for disease diagnosis, including observation of gross signs (level I), bacterial isolation (level II), qPCR and 16S rDNA sequencing (level III). The result showed that 7/7 affected farms (three Asian seabass farms and four tilapia farms) experiencing clinical signs of streptococcosis were diagnosed positive for S. iniae. qPCR assays using DNA extracted directly from fish tissue detected S. iniae in 11 out of 36 fish samples (30.6%), while 24 out of 36 samples (66.7%) tested positive after an enrichment step, including apparently healthy fish from affected farms. Bacterial isolation of S. iniae was only successful in a proportion of clinically diseased fish but not in healthy-looking fish from the same farm. Overall, the newly developed qPCR protocol combined with enrichment would be a useful tool for the diagnosis and surveillance of S. iniae infections in fish populations, thereby aiding in the disease control and prevention.

Cytotoxicity and immunological impact of Trypanosoma sp. infection on blood parameters of wild African catfish, Clarias gariepinus.

Fish trypanosomiasis is a common blood parasitic disease transmitted by aquatic invertebrates, such as leeches. This study aims to shed light on the cytotoxicity of Trypanosoma sp. on erythrocytes and its impacts on the innate immune response (serum lysozyme activity, nitric oxide production, phagocytic activity, serum total protein, and globulin) in wild African catfish, Clarias gariepinus. One hundred catfish were examined using blood smears stained with Giemsa and confirmed with PCR. The prevalence of infection was found to be 10% by microscope detection and 15% by PCR. The morphological identification of Trypanosoma as Trypanosoma mukasai was determined. Additionally, this study included previously undescribed features of Trypanosoma, such as the width of the anterior and posterior body, the length of the posterior pale region, and the number of folds. Various alterations in erythrocytes were observed, totaling 54.57%. Nuclear abnormalities, including fragmented nuclei, eccentric nuclei, and micronuclei, were also reported. Infected fish showed a reduction in serum total protein and globulin levels, while nitric oxide production, lysozyme activity, and phagocytic activity exhibited a significant increase compared to non-infected fish. We believe that our findings will contribute valuable data to the morphological and molecular identification of Trypanosoma sp. in African catfish, as well as their cytotoxic impact.

Histological and hematological changes to Clarias gariepinus juveniles exposed to acute doses of Emamectin benzoate in a static bioassay.

Emamectin benzoate (EMB) is a potent neurotoxic pesticide, extensively used in agriculture and aquaculture in Nigeria. The knowledge of its toxicological impact to C. gariepinus in Nigeria is scarce. Thus, the investigation was designed to uncover its 96 h LC50, safe level to aquatic media, histological impact on fish liver, gill and hematological changes in the blood parameters. 96 h LC50 was 0.34 mg L-1. Safe level of EMB was 0.034 mg L-1. Dose dependent liver degenerations were characterized by; Congestion of the central vein by inflammatory cells, pyknotic nuclei of hepatocytes, coagulation necrosis, focal necrosis, dilations of sinusoidal spaces and infiltration of periportal regions by inflammatory cells. Dose dependent changes in gill were characterized by; mucus secretion, shrinkage of secondary lamellae, hyperplasia, occlusion of secondary lamellae, degeneration of gill cartilage, necrosis of respiratory epithelia and erosion of secondary lamellae. Red blood cell indices decreased minimally at the end of the 96 h exposure. White blood cell count (WBCC), mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were significantly (p ≤ 0.05) elevated in three treatments. Neutrophils decreased significantly (p ≤ 0.05), basophils, eosinophils and monocytes showed mixed tendencies. The findings of this investigation imply that C. garipinus exposed to EMB may cause dose and time-dependent changes in the liver and gill histology as well as alterations in the fish's hematological profile, all of which were harmful to the fish's health. To avoid negative effects on fish in nearby aquatic settings, it is advised that the use of EMB be monitored and limited.

Wearable Bioimpedance-Based Deep Learning Techniques for Live Fish Health Assessment under Waterless and Low-Temperature Conditions.

(1) Background: At present, physiological stress detection technology is a critical means for precisely evaluating the comprehensive health status of live fish. However, the commonly used biochemical tests are invasive and time-consuming and cannot simultaneously monitor and dynamically evaluate multiple stress levels in fish and accurately classify their health levels. The purpose of this study is to deploy wearable bioelectrical impedance analysis (WBIA) sensors on fish skin to construct a deep learning-based stress dynamic evaluation model for precisely estimating their accurate health status. (2) Methods: The correlation of fish (turbot) muscle nutrients and their stress indicators are calculated using grey relation analysis (GRA) for allocating the weight of the stress factors. Next, WBIA features are sieved using the maximum information coefficient (MIC) in stress trend evaluation modeling, which is closely related to the key stress factors. Afterward, a convolutional neural network (CNN) is utilized to obtain the features of the WBIA signals. Then, the long short-term memory (LSTM) method learns the stress trends with residual rectification using bidirectional gated recurrent units (BiGRUs). Furthermore, the Z-shaped fuzzy function can accurately classify the fish health status by the total evaluated stress values. (3) Results: The proposed CNN-LSTM-BiGRU-based stress evaluation model shows superior accuracy compared to the other machine learning models (CNN-LSTM, CNN-GRU, LSTM, GRU, SVR, and BP) based on the MAPE, MAE, and RMSE. Moreover, the fish health classification under waterless and low-temperature conditions is thoroughly verified. High accuracy is proven by the classification validation criterion (accuracy, F1 score, precision, and recall). (4) Conclusions: the proposed health evaluation technology can precisely monitor and track the health status of live fish and provides an effective technical reference for the field of live fish vital sign detection.

Hepatic, Muscle and Intestinal Oxidative Status and Plasmatic Parameters of Greater Amberjack (Seriola dumerili, Risso, 1810) Fed Diets with Fish Oil Replacement and Probiotic Addition.

The present study was conducted to investigate the effects of dietary fish oil replacement with a mixture of vegetable oils and probiotic supplementation on plasma biochemical parameters, oxidative stress, and antioxidant ability of Seriola dumerili. Specimens with an initial weight of 175 g were used. Four feeds were formulated with 0% (FO-100), 75% (FO-25), and 100% (FO-0 and FO-0+ with the addition of Lactobacillus probiotics) substitution of fish oil with a mixture of linseed, sunflower, and palm oils. After 109 days, no significant differences were observed in the activity of antioxidant enzymes in the liver, foregut, and hindgut, only glucose-6-phosphate dehydrogenase activity in the liver was higher in the fish fed the FO-100 diet than in those fed the FO-0 diet. No significant differences were observed in the total, reduced, and oxidized glutathione and the oxidative stress index in the liver. In addition, lipid peroxidation in the liver and red muscle values were higher in the fish fed the FO-100 diet than in the fish fed the FO-0+ diet, however, the foregut of the fish fed the FO-100 diet presented lower values than that of the fish fed the FO replacement diet, with and without probiotics. There were significant differences in cholesterol levels in the FO-100 group; they were significantly higher than those observed with the fish diets without fish oil. To sum up, fish oil can be replaced by up to 25% with vegetable oils in diets for Seriola dumerili juveniles, but total fish oil substitution is not feasible because it causes poor survival. The inclusion of probiotics in the FO-0+ diet had no effects on the parameters measured.

In-feed emamectin benzoate abuse affects the biological responses and erythrocytes of Nile tilapia Oreochromis niloticus.

In aquaculture, drugs are often abused to accomplish disease control without considering the negative effects on fish health. This study aimed at elucidating the pernicious effects of in-feed antiparasitic drug emamectin benzoate (EB) abuse on the haemato-biochemistry and erythro-morphometry of healthy Nile tilapia Oreochromis niloticus. The fish were fed EB at 50 µg (1×) and 150 µg/kg biomass/d (3×) for 14 d as against the recommended 7 d and periodically assessed the blood parameters. A significant dose- and time-dependent reduction in feed intake, survival, total erythrocytes (TEC), monocytes (MC), hemoglobin (Hb), hematocrit (Ht) and mean corpuscular Hb concentration were noted. The total leukocytes (TLC), thrombocytes (TC), lymphocytes (LC) and neutrophils (NC) markedly augmented. The EB-dosing altered the fish physiology by enhancing the glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and creatinine and reducing the calcium, chloride and acetylcholinesterase (AChE) levels dose-dependently. The fish recovered within 4 weeks in the 1× group post-dosing but persevered in the overdosed group. The erythro-cellular and nuclear dimensions were reduced with the increase in dose and normalized after the cessation of dosing, except for nuclear volume. The erythro-morphological alterations were more prominent in the overdosed group. The results implied the pernicious effect of oral EB medication on the biological responses of fish if abused.

Contamination of selected heavy metals in Limnothrissa miodon (Boulenger, 1906) in the four strata of Lake Kariba Zambia: are the consumers at risk?

Pollution of aquatic ecosystems is one of the major challenges affecting many countries of the world. Heavy metal pollutants, in particular, threaten the life of aquatic organisms (fauna and flora) and, more importantly, humans who consume aquatic products as a critical source of proteins. In the present study, the concentrations of selected heavy metals (cobalt- Co, Chromium-Cr, nickel- Ni and manganese- Mn) in Limnothrissa miodon, locally known as 'Kapenta' were assessed using the Microwave Plasma Atomic Emission Spectrometer (MP AES) 4200 at the Zambia Agricultural Research Institute (ZARI). The fish was collected from Lake Kariba, Zambia, which is divided into four fisheries management strata (I, II, III, and IV). The health risks to consumers were evaluated using the Estimated Daily Intake (EDI), Target Hazard Quotient (THQ) and Hazard Index (HI). Analysis of variance (ANOVA) was used to assess the difference in the means of heavy metal concentration across the four strata for each element. The concentrations of all the heavy metal elements were within the permissible limits considered to be safe for human consumption based on the Food and Agriculture Organization (FAO) standards. However, the concentration of individual heavy metal elements varied significantly across the strata with stratum I and II showing higher levels in general except for Mn which was highest in stratum II and III compared with the other strata. Furthermore, Mn concentration was the highest in all the strata and the highest concentration was observed in the fish from stratum II. The EDIs, THQs and HIs of each heavy metal element did not show any threat to consumers of the fish from the lake. Further studies are required to better understand the potential sources of heavy metals and to regularly monitor existing activities that may elevate the concentration levels.