Fish Health Assessment Research Articles

Non-lethal biomarkers as promising tools for fish health assessment: In situ exposure to bifenthrin as a case study

Non-lethal biomonitoring should provide an innovative approach to establish bioethical protocols for the management of both aquaculture and wild fisheries resources. We aimed to assess non-lethal biomarkers in Piaractus mesopotamicus caged in a rice field during a bifenthrin (BF) application. We analyzed parameters related to the immune system, energy metabolism and oxidative stress in fish skin mucus and blood plasma. Fish exposed to BF showed a significant increase in skin mucus glucose levels and the enzymatic activities of protease, alkaline phosphatase and superoxide dismutase. Regarding plasmatic parameters, BF increased the levels of glucose, total protein and albumin, but decreased triglycerides. In addition, increased activities of lysozyme and alkaline phosphatase were found in the blood plasma of exposed fish. Our results indicated an increased energy demand, altered immune function and a mild oxidative stress response in fish exposed in situ to BF. We have shown that skin mucus and blood plasma are very promising matrices for the development of non-lethal biomarkers to assess fish health in a stressed environment.

POLO: Pose estimation with one-stage location-sensitive coding

The precise monitoring of fish keypoints and behavioral patterns is crucial in fish farming, influencing decisions on feeding schedules and assessing fish health. Traditional approaches to multi-object pose estimation often lean towards either Bottom-up or Top-down methods. Our innovative solution introduces a streamlined single-stage multi-object pose estimation framework, utilizing a unique approach to instance assignment based on location. By incorporating position encoding as an index for candidate pose heatmap groups, we achieve end-to-end multi-object pose estimation with reduced redundancy through non-maximum suppression. Our framework, named POLO, has been validated on a meticulously annotated fish keypoint dataset, demonstrating outstanding performance with a remarkable 65.34% OKS AP at 71.4 FPS on Tesla v100. With its real-time capabilities, POLO is highly adaptable, making it suitable for deployment on various edge computing devices and addressing real-world challenges effectively. We believe our framework can serve as a solid baseline for diverse pose estimation tasks across different domains.

Multispecies and multibiomarker assessment of fish health from Iguaçu River reservoir, Southern Brazil.

This study investigated the impact of micropollutants on fish health from Segredo hydroelectric reservoir (HRS) along the Iguaçu River, Southern Brazil, contaminated by urban, industrial, and agricultural activities. This is the first comprehensive study assessment in the river after the severe drought in the 2020s in three fish species from different trophic levels Astyanax spp. (water column depth/omnivorous), Hypostomus commersoni (demersal/herbivorous), and Pimelodus maculatus (demersal/omnivorous). Animals, water, and sediment samples were collected from three distinct sites within the reservoir: Floresta (upstream), Iratim (middle), and Station (downstream). The chemical analysis revealed elevated concentrations of metals (Al, Cu, Fe) and the metalloid As in water, or Cu, Zn, and As in sediment, surpassing Brazilian regulatory limits, while the organic pollutants as DDT, PAHs, PCBs, and PBDEs were found under the Brazilian regulatory limits. The metal bioaccumulation was higher in gills with no significant differences among sites. The species Astyanax spp. and H. commersoni displayed variations in hepatosomatic index (HSI) and P. maculatus in the condition factor index (K) between sites, while adverse effects due to micropollutants bioaccumulation were observed by biochemical, genotoxic, and histopathological biomarkers. The principal component analysis and integrated biomarker response highlighted the upstream site Floresta as particularly inhospitable for biota, with distinctions based on trophic level. Consequently, this multifaceted approach, encompassing both fish biomarkers and chemical analyses, furnishes valuable insights into the potential toxic repercussions of micropollutant exposure. These findings offer crucial data for guiding management and conservation endeavors in the Iguaçu River.

Visualization of poikilocytosis as an emerging erythrocytic biomarker for fish health assessment

AbstractFish health assessment is essential for maintaining sustainable aquatic ecosystems and ensuring the well‐being of wild and farmed fish populations. Hematological parameters are crucial indicators of fish health, with poikilocytosis emerging as a fundamental marker with significant diagnostic value. Poikilocytosis refers to abnormally shaped erythrocytes in bloodstream, reflecting underlying physiological and pathological conditions. Poikilocytosis can occur in various fish species and can be influenced by environmental stressors, infectious agents, nutritional deficiencies, and exposure to pollutants. Morphological alterations in erythrocytes, such as acanthocytes, echinocytes, dacrocytes, schistocytes, spherocytes, and codocytes are common poikilocytes in fish. Understanding the relationship between poikilocytosis and fish health has important implications for disease diagnosis, monitoring, surveillance, and management. By quantifying poikilocytic changes, researchers and veterinarians can differentiate normal variations from pathological conditions, facilitating targeted interventions and treatment strategies. While most studies have focused on heavy metal toxicity, stressors, nutritional deficiencies, pollutants, and therapeutics, the etiological induction of poikilocytosis in fish health has been overlooked. Nonetheless, poikilocytosis remains a valuable biomarker for assessing fish health and their environment. This review highlights piscine poikilocytosis as a significant fish hematological biomarker and its importance in understanding their health and culture conditions.

A systematic review of approaches to assess fish health responses to anthropogenic threats in freshwater ecosystems.

Anthropogenic threats such as water infrastructure, land-use changes, overexploitation of fishes and other biological resources, invasive species and climate change present formidable challenges to freshwater biodiversity. Historically, management of fish and fishery species has largely been based on studies of population- and community-level dynamics; however, the emerging field of conservation physiology promotes the assessment of individual fish health as a key management tool. Fish health is highly sensitive to environmental disturbances and is also a fundamental driver of fitness, with implications for population dynamics such as recruitment and resilience. However, the mechanistic links between particular anthropogenic disturbances and changes in fish health, or impact pathways, are diverse and complex. The diversity of ways in which fish health can be measured also presents a challenge for researchers deciding on methods to employ in studies seeking to understand the impact of these threats. In this review, we aim to provide an understanding of the pathway through which anthropogenic threats in freshwater ecosystems impact fish health and the ways in which fish health components impacted by anthropogenic threats can be assessed. We employ a quantitative systematic approach to a corpus of papers related to fish health in freshwater and utilize a framework that summarizes the impact pathway of anthropogenic threats through environmental alterations and impact mechanisms that cause a response in fish health. We found that land-use changes were the most prolific anthropogenic threat, with a range of different health metrics being suitable for assessing the impact of this threat. Almost all anthropogenic threats impacted fish health through two or more impact pathways. A robust understanding of the impact pathways of anthropogenic threats and the fish health metrics that are sensitive to these threats is crucial for fisheries managers seeking to undertake targeted management of freshwater ecosystems.

Comprehensive Colony Health Management and Emerging Pathogens of the Annual Killifish Species Nothobranchius furzeri.

The Leibniz Institute on Aging has maintained killifish colonies for over 15 y. Our veterinarians, scientists, and animal technicians developed a fish health scoring system and routine colony health surveillance program for our colonies. Over a 4-y period, health data from the African turquoise killifish Nothobranchius furzeri colony were systematically collected and analyzed. The fish health assessment system facilitated categorization of clinical signs and differentiation of fish with mild clinical signs from fish that required euthanasia. This report provides new information on clinical signs and conditions that may occur in young and aged N. furzeri. To be comprehensive, a colony health surveillance program incorporates animal health at both the individual and the population levels. The quarterly routine health monitoring program identified Mycobacterium spp. as the most common agent in our facility and identified the killifish pathogen (Loma acerinae) for the first time. Taken together, these findings demonstrate the importance of a comprehensive colony health management system in a fish research facility. By improving the health and welfare of fish used for research, the scientific community will benefit from less variable and more reliably reproducible research results.

A Deep Survey of Fish Health for the Recognition of Useful Biomarkers to Monitor Water Pollution

The aim of the present study was to evaluate the wild freshwater fish health status using a vast array of biomarkers as predictive factors of pollutant exposure. The European eel (Anguilla anguilla) and brown trout (Salmo trutta fario), resident in rivers with different degrees of pollution in the South of Italy (Picentino River with good environmental quality and Tusciano River with low environmental quality), were examined using biometric parameters, histopathological and immunohistochemical biomarkers to evaluate the health status and a possible correlation with the water quality. Several alterations identified in the liver positively correlated with water and soil pollutants: hemorrhage (p ≤ 0.05), cytoplasmic vacuolization (p ≤ 0.01), hemosiderosis (p ≤ 0.05), irregular arrangement of hepatocytes (p ≤ 0.01), lipid accumulation (p ≤ 0.05), necrosis (p ≤ 0.01), cellular hyperplasia (p ≤ 0.05), leukocyte infiltration (p ≤ 0.01) and melanomacrophages centers (MMC) (p ≤ 0.01). In the spleen, only hemosiderosis correlated with water and soil pollutants (p ≤ 0.05). The inflammatory biomarker tumor necrosis factor α (TNFα) and ciclooxigenase 2 (COX2) responded to the environmental pollution, as well as the oxidative stress biomarkers superoxide dismutase (SOD2) and 8-Hydroxy-2′-deoxyguanosine (8-OHdG). Erythrocytic nuclear abnormalities and erythrocytic cellular abnormalities were found to be significantly higher in the blood of both the European eel (p < 0.0001) and brown trout (p < 0.001) in the Tusciano River compared with the Picentino River. Taken together, these results outline the need to increase the number of suitable biomarkers to assess fish health and reinforce the importance of employing additional biomarkers in biomonitoring programs that can be applied to evaluate water quality and in environmental assessment around the world.

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.

Health of wild fish exposed to contaminants of emerging concern in freshwater ecosystems utilized by a Minnesota Tribal community.

Fish serve as indicators of exposure to contaminants of emerging concern (CECs)-chemicals such as pharmaceuticals, hormones, and personal care products-which are often designed to impact vertebrates. To investigate fish health and CECs in situ, we evaluated the health of wild fish exposed to CECs in waterbodies across northeastern Minnesota with varying anthropogenic pressures and CEC exposures: waterbodies with no human development along their shorelines, those with development, and those directly receiving treated wastewater effluent. Then, we compared three approaches to evaluate the health of fish exposed to CECs in their natural environment: a refined fish health assessment index, a histopathological index, and high-throughput (ToxCast) in vitro assays. Lastly, we mapped adverse outcome pathways (AOPs) associated with identified ToxCast assays to determine potential impacts across levels of biological organization within the aquatic system. These approaches were applied to subsistence fish collected from the Grand Portage Indian Reservation and 1854 Ceded Territory in 2017 and 2019. Overall, 24 CECs were detected in fish tissues, with all but one of the sites having at least one detection. The combined implementation of these tools revealed that subsistence fish exposed to CECs had histological and macroscopic tissue and organ abnormalities, although a direct causal link could not be established. The health of fish in undeveloped sites was as poor, or sometimes poorer, than fish in developed and wastewater effluent-impacted sites based on gross and histologic tissue lesions. Adverse outcome pathways revealed potential hazardous pathways of individual CECs to fish. A better understanding of how the health of wild fish harvested for consumption is affected by CECs may help prioritize risk management research efforts and can ultimately be used to guide fisherymanagement and public health decisions. Integr Environ Assess Manag 2024;20:846-863. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Fish Monitoring from Low-Contrast Underwater Images

A toolset supporting fish detection, orientation, tracking and especially morphological feature estimation with high speed and accuracy, is presented in this paper. It can be exploited in fish farms to automate everyday procedures including size measurement and optimal harvest time estimation, fish health assessment, quantification of feeding needs, etc. It can also be used in an open sea environment to monitor fish size, behavior and the population of various species. An efficient deep learning technique for fish detection is employed and adapted, while methods for fish tracking are also proposed. The fish orientation is classified in order to apply a shape alignment technique that is based on the Ensemble of Regression Trees machine learning method. Shape alignment allows the estimation of fish dimensions (length, height) and the localization of fish body parts of particular interest such as the eyes and gills. The proposed method can estimate the position of 18 landmarks with an accuracy of about 95% from low-contrast underwater images where the fish can be hardly distinguished from its background. Hardware and software acceleration techniques have been applied at the shape alignment process reducing the frame processing latency to less than 0.5 us on a general purpose computer and less than 16 ms on an embedded platform. As a case study, the developed system has been trained and tested with several Mediterranean fish species in the category of seabream. A large public dataset with low-resolution underwater videos and images has also been developed to test the proposed system under worst case conditions.

Expression of Interleukin-1β protein in vitro,exvivo and in vivo salmonid models

Interleukin-1β (IL-1β) is one of the first cytokines expressed during immune responses, and its levels are affected by many factors, including stress. To date, it has only been possible to measure IL-1β transcript (mRNA) expression quantitatively in fish using qPCR. This is because previous studies that measured IL-1β protein concentrations in these taxa used western blotting, which only provides qualitative data. To advance our knowledge of fish IL-1β biology, and because post-translational processing plays a critical role in the activation of this molecule, we developed a quantitative enzyme-linked immunosorbent assay (ELISA) to accurately measure the concentration of IL-1β protein in several cell cultures and in vivo in salmonids. We compared changes in IL-1β protein levels to the expression of its mRNA. The developed ELISA was quite sensitive and has a detection limit of 12.5 pg/mL. The tools developed, and information generated through this research, will allow for a more accurate and complete understanding of IL-1β′s role in the immune response of salmonids.The assay described here has the potential to significantly advance our ability to assess fish health and immune status.

Does the site of blood collection and sex of crucian carp (Carassius carassius) affect hematological and blood biochemical results?

Abstract Blood analysis is used to evaluate the effects of various environmental factors on fishes and to assess fish health and welfare. Fish blood is routinely sampled from the caudal vein or the heart. The aim of the present study was to determine the differences between venous and cardiac crucian carp (Carassius carassius (L.)) blood parameters. Additionally, the influence of sex was tested. The fish were divided into two groups: group I consisted of 10 males and 9 females, group II consisted of 8 males and 8 females. The fish from group I had blood sampled first from the caudal vein and then from the heart. The fish from group II had the procedures in the opposite order. The hematological parameters determined in the present study depended on the blood collection site and the sex of the individuals. Blood biochemical indices depended on the sex of the fish but not on the blood sampling site. The effect of sampling order was observed in the case of both hematological and biochemical parameters. The results of the current study indicated that the blood collection site, the sex of fish, and sampling order should be taken into consideration in hematological experiments.

Perfil de glicose no sangue como um método rápido para observar o estado de saúde de carpa Koi (Cyprinus carpio) - estudo de caso de ectoparasitos em Blitar, Indonésia

Assessment of fish health is one of the efforts of farmers in minimizing losses due to disease. Rapid tests on fish health can be done through blood observations. This study aimed to determine the blood glucose profile of koi carp due to ectoparasite infestation from the level of blood glucose. The results showed that reported parasites from Blitar's koi carp were Trichodina, Dactylogyrus, Gyrodactylus, Myxobolus, Thelohanellus, Ichthyophthirius, and Argulus. Trichodina showed the highest prevalence (100%) in this case while Thelohanellus was the highest intensity level (93.8±16.3). The results of blood glucose level measurement based on parasite infestation levels showed no significant difference (p>0.05) though the health problems caused by parasites in light, medium or heavy infestation. This research also indicated that the blood glucose profile could be used as a rapid method to detect fish health caused by parasites. We suggest that other variables such as nutritional status, life stage or feeding must be conducted to ensure the glucose role in parasite identification as a rapid method for the future work.

Necrosis Incidence on The Tail Fin of Sand Lobster (Panulirus homarus) Reared Using Recirculating Aquaculture System (RAS)

Lobster rearing has been widely carried out in Indonesia, especially to prevent a decrease in stocks in nature due to fishing that does not pay attention to the aspect of resource sustainability. However, in the effort to rear lobsters, there are obstacles, namely necrosis to the tail fins of sand lobsters reared with recirculation aquaculture system (RAS) caused by infectious diseases. This research was carried out at the Field Test Facility of Fish Health and Environmental Assessment Center (BPKIL) Serang in June-November 2021. Sand lobsters had an initial size of 50-100 grams which were reared in 1000-L fiberglass tanks with a density of 25 individuals per tank and reared with RAS. Samples from diseased sand lobster after being reared in RAS for 176 days. Necrosis (red color and erosive) can be seen in the tail fins of sand lobsters reared with the RAS. From the results of laboratory tests, it was found that there were parasitic infections of the types of ciliates, protozoa, and vorticella. The results of further testing at the Microbiology Laboratory found that there was an infestation of vibriosis disease caused by the bacteria Vibrio alginolyticus and Vibrio parahaemolyticus. Diseases caused by parasitic and bacterial attacks do not affect mass death in sand lobsters, even these symptoms can disappear if sand lobsters can replace their skin (moulting) perfectly. Observations also show that the most mortality occurred in sand lobsters with smaller sizes (weight ≤100 grams). This disease infection occurred due to a decrease in the water quality of the sand lobster rearing media in RAS, mainly because of the high organic matter concentration in the water.

Assessment of the physiological markers, oxidative stress and neurotoxic effects of nematode Anisakis sp. on the Luciobarbus callensis (Teleosts, Cyprinids) in northeast of Algeria

Our study focused on the effect of parasites on the antioxidant system and their neurotoxic effect in Luciobarbus callensis (Teleosts, Cyprinids). In this context, cellular biomarkers, acetylcholinesterase (AChE), catalase (CAT), molecules H2O2 as well as morphophysiological markers (condition factor (FC), hepatosomatic index (HSI), splenosomatic index (SSI), viscerosomatic index (VSI) were analyzed in fish infested with L3 larvae of Anisakis sp., nematodes of marine organisms, captured in Lake Oubéira (Algeria). The results showed a significant decrease in AChE activities in the heart (68 % p < 0.05) and muscles (81.55 % p < 0.05) in infested fish compared to those recorded in reference fish. In contrast, splenic AChE levels were significantly induced. CAT levels were significantly decreased in the spleen (73 % p < 0.05) and intestine (56 % p < 0.05) of fish parasitized by Anisakis sp. compared to healthy fish. HSI and SSI were significantly higher in healthy fish. On the other hand, Anisakis sp. had no significant effect on FC and VSI at the time of sampling. This study suggests that antioxidant defense disorders (CAT), due to a direct inhibitory action of nematode toxic products on this molecule and an increase in ROS production in these animals, leading to a high pro-oxidant state (H2O2), causing neurological effects (AChE) with enlargement of the spleen and liver of infested barb. In this regard, monitoring the effect of parasitic infections on physiological and biochemical marker profiles can be a crucial means of assessing fish health under natural conditions; to ensure the conservation and sustainability of aquatic biodiversity, including fish farming and artificial production.

Effects of aquaponic system on fish locomotion by image-based YOLO v4 deep learning algorithm

• Explored the comparison of water quality between aquaponic system and recirculating aquaculture system. • Proposed a method for detecting fish locomotion based on deep learning. • Explore the influence of aquaponic system on fish locomotion and biological characteristics. • Provide a reference for the balance of aquaponic system to achieve maximum benefits. Fish locomotion analysis can provide important information for aquaculture managers to make effective production decision. However, the existing aquaponic system work mainly focuses on the transformation of nitrogen elements and are limited because their complex inspection procedures, it is rarely reported to explore effects of aquaponic system on fish locomotion. Using automated methods to explore the effect of aquaponic system on fish locomotion is a challenging task. To address this research gap, we examined and compared fish locomotion in aquaculture with different systems, i.e., aquaponic system and recirculating aquaculture system based on computer vision. The statistical results of fish locomotion in the two systems showed that the fish locomotion in aquaponic systems is significantly higher than that in recirculating aquaculture system, primarily due to the certain purification effect of plants and microorganisms on water quality. In addition, under the same conditions in the aquaculture system aquaponic system had stronger nitrogen absorption capacity than recirculating aquaculture system, the average multiple of the water quality parameter concentration of nitrate nitrogen, total nitrogen and total phosphorus in RAS are 1.79, 1.58, 1.81 times that of APS, from the stability of the experimental system to the end of the experiment.. The error of our proposed method of calculating fish locomotion is less than 5%. Overall, this is the first automated intensive monitoring method that examined the role aquaponic system played in fish locomotion, which could assess fish health based on the locomotion to further fine tune the planting density of aquaponics to achieve the maximum benefit.

Assessing Stress Resilience After Smolt Transportation by Waterborne Cortisol and Feeding Behavior in a Commercial Atlantic Salmon (Salmo salar) Grow-Out Recirculating Aquaculture System.

Sampling protocols and water quality sensors have been developed to assess fish health and welfare in recirculating aquaculture systems (RASs). Still, the use of fish-based non-invasive welfare indicators, reflecting the physiological state of the fish, is limited in this type of system. Cortisol, the major stress-coping hormone in fish, diffuses through the gills. Consequently, waterborne cortisol is a potential fish-based non-invasive welfare indicator in RAS. However, its use in commercial rearing systems is sparse. In this study, we evaluated water cortisol levels and feeding behavior as welfare indicators of newly inserted smolt in a commercial RAS for harvest size Atlantic salmon. The RAS consisted of two parallel fish rearing raceways, raceways 1 and 2, sharing the same water treatment with common outlets and inlets. The smolts were inserted in raceway 1 while salmon that have been in the system for 6 months or more were kept in raceway 2. The smolt insertion period was 3 days. Samples for water cortisol levels were withdrawn the day before, 1 and 3 days after the smolt insertion period. Smolt insertion resulted in elevated water cortisol concentrations in the entire system, with the highest values in raceway 1, one day after smolt insertion. Estimated cortisol production in newly inserted smolt decreased over time, was similar to what has been reported in salmon adapting to experimental tanks. Feeding behavior indicated that the appetite was not fully resumed in the newly inserted smolts, while the appetite of fish in raceway 2 was unaffected by smolt insertion. These results, obtained in a highly intensive commercial RAS, suggest that waterborne cortisol together with feeding behavior can be used as indicators for adaptive processes associated with stress resilience in farmed fish. Thus, they are promising non-invasive indicators for assessing the impact of potential stressors on fish welfare in this type of rearing system.

Does blood sampling from caudal vessels in fish produce parameter values different from those obtained by heart puncture?

Analyses of blood samples in ichthyology are of importance for assessment of fish health as well as fish responses to environmental stressors. The measurement results may be affected by multiple factors. This study aimed at assessment of the influence of the blood collection site by comparing dual values of indices measured in samples obtained both from the heart and puncturing caudal vessels in the same fish specimens. Our results revealed that the sampling site did not significantly influence measured variables including haematological indices, the plasma biochemistry profile, acid-base balance parameters and the phagocytic activity. To conclude, for the rainbow trout (Oncorhynchus mykiss) both sampling methods are interchangeable with regard to the above-mentioned indices.

Multifactorial causes of an emaciated wild Lutjanus erythropterus in Oman

AbstractPostmortem examination of a wild Lutjanus erythropterus exhibiting emaciation associated with multifactorial causes is presented. Skeletal muscle analysis for heavy metals revealed presence of threefold cadmium concentration in comparison with the European standards. Multifocal necrosis and muscle atrophy (condition factor K = 0.92) were also noted. Other anomalies recorded included abdominal distension and bilateral sunken eyes. The liver showed scant vacuolation, melano‐macrophage centres and diffuse granulomatous lesions also occurring in the viscera and mesenteries. Intensity of infection varied from 2 to 9 parasites, while 16S rRNA sequences revealed the opportunistic pathogen Photobacterium damselae complex only in affected organs. This is the first record of non‐aetiologic and aetiologic factors occurring concurrently in a wild fish in Oman. Although no definitive conclusions can be drawn, these findings highlight the urgent need for further fish health assessment regarding these pathologies and other diseases that pose a health risk to other fish species.

Evaluation of Behavioral Changes and Tissue Damages in Common Carp (Cyprinus carpio) after Exposure to the Herbicide Glyphosate.

Pesticides can induce changes in behavior and reduce the survival chance of aquatic organisms. In this study, the toxic effects of glyphosate suspension (Glyphosate Aria 41% SL, Tehran Iran) on behavior and tissues of common carp (Cyprinus carpio) were assessed. For this purpose, a 96 h LC50 of glyphosate suspension (68.788 mL·L−1) was used in the toxicity test. All individuals were divided into control and treatment groups with four replicates. Exposure operations were performed under two conditions: increasing concentration of suspension from 0 to 68.788 mL·L−1; then, decreasing to the first level. The swimming pattern was recorded by digital cameras during the test and tissue samples were collected at the end of the test. There were significant differences between the swimming pattern of treated individuals and control ones during both steps. The sublethal concentration of glyphosate led to hypertrophy, hyperplasia and hyperemia in the gill of fish. However, changes were obvious only after sampling. The exposed fish also displayed clinical signs such as darkening of the skin and increasing movement of the operculum. Moreover, glyphosate suspension affected swimming patterns of fish suggest that the swimming behavior test can indicate the potential toxicity of environmental pollutants and be used as a noninvasive, useful method for managing environmental changes and assessing fish health conditions by video monitoring.