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We conducted a study to investigate the potential effects of nutrients released from a fish farm, which fell within the typical range found in oligotrophic offshore waters of the Aegean Sea, on phytoplankton growth. We designed an in situ bioassay experiment at a fish farm and incubated natural phytoplankton assemblages inside dialysis membrane bags for six days. Changes in phytoplankton growth in samples of ambient seawater collected throughout the experiment served as controls and were considered indicative of the net population change rates. Half of the bags were filled with seawater filtered through a 150-µm mesh, while the other half contained unfiltered seawater. The growth rates, estimated based on chlorophyll a concentrations and phytoplankton cell numbers inside the filtered and unfiltered bags, showed no significant differences. While no detectable net phytoplankton growth occurred in the ambient seawater, there was an exponential increase in chlorophyll a content and cell numbers within the bags. Moreover, the species richness within the bags gradually declined throughout the experiment. The findings of the study confirm that continuous nutrient releases from fish farms can promote high population growth rates in oligotrophic environments, provided that phytoplankton losses due to grazing, advection, and sinking are minimized or eliminated. [ABSTRACT FROM AUTHOR]

ABSTRACT Environmental temperature shapes the ontogeny of ectotherms by influencing rates of growth and development which can be key determinants of survival. Whereas the escalating impacts of water management on freshwater ecosystems is well documented, the effects of cold‐water releases from dams—which can alter downstream temperatures—remains relatively underexplored but may present novel challenges to endemic ectotherms. Specifically, little is known about how thermal depressions reshape phenotypic and genetic patterns during larval metamorphosis for fishes that evolved in warmwater systems. We assessed the effects of thermal shifts on larval ontogeny of the endangered razorback sucker (Xyrauchen texanus), which evolved in the warm waters of the Colorado River Basin, USA. We hypothesised that development is more sensitive to cold‐water influences than growth and that temperature would influence patterns in gene expression related to development. Our results supported these hypotheses and showed that both wild and laboratory‐reared larvae in slightly cooler temperatures exhibited delayed development, but similar growth compared to larvae reared in warmer conditions. These findings suggest growth and development in early ectotherm life stages can be decoupled, which follows patterns more like the temperature‐size rule than allometric scaling of development by size. We also observed transcriptional differences related to genes associated with stress responses and development in our laboratory‐reared fish; here, gene expression of fish from the coldest conditions at the end of the experiment was more similar to fish reared in warmer temperatures at the midpoint. Our findings suggest that modest temperature reductions can delay ontogeny and alter the transcriptional landscape while not necessarily limiting growth. This finding highlights the need for conservation practitioners to consider cascading impacts that even small temperature reductions can cause in riverine ecosystems. [ABSTRACT FROM AUTHOR]

The quality of water used in aquaculture ponds is one of the crucial factors influencing the smell and sensory properties of fish. The water samples were taken from the rainbow trout fish ponds from three different fish farms in three provinces in Türkiye in four different seasons. The samples were analyzed for the volatile components by employing HS-SPME/GC–MS. Seven different volatile groups including aldehydes, ketones, esters, alcohols, volatile phenols, terpenes and other aromatic substances were identified in the samples. Among these, aldehydes were found to be the most dominant. (E)-2-Heptenal, nonanal, acetophenone, and 2-ethyl-1-hexanol are thought to be responsible for the off-odors in the water that have the potential to cause off-odors in fish. It was also determined that the amounts of these compounds increases in winter due to lower water temperature. Fish producers should monitor water quality on a regular basis to prevent off-odor compounds that degrade fish quality. [ABSTRACT FROM AUTHOR]

The genus Megalocytivirus, belonging to the family Iridoviridae, is one of the most detrimental virus groups to fish aquaculture. Megalocytivirus creates a virus-mock basement membrane (VMBM) on the surface of infected cells. This membrane provides attachment sites for lymphatic endothelial cells (LECs), disrupting fish's endothelial cell-extracellular matrix system. This disruption triggers injury to the vascular system and can result in death. Exploring the VMBM-cell interaction mechanism is crucial for uncovering the pathogenesis of Megalocytivirus and identifying therapeutic targets. Claudins, a class of tetra transmembrane proteins, play a key role in creating tight junctions between endothelial or epithelial cells. In this study, we demonstrated that the expression of Claudin2, a member of the Claudin family in fish, was significantly up-regulated by Megalocytivirus infection. Claudin2 was found in LECs attached to the surface of infected cells. It interacted with the VMBM viral components VP23R, VP08R, and VP33L at multiple binding sites through its two extracellular loops. However, it did not interact with the host basement membrane's nidogen. Therefore, Claudin2 is involved in the interaction of LEC with VMBM and plays a role in the disturbed distribution of extracellular matrix and endothelial cells in Megalocytivirus-infected fish tissues. This study aims to uncover the molecular mechanisms by which Megalocytivirus infection leads to pathological changes in the vascular system. [ABSTRACT FROM AUTHOR]

In vitro cell culture systems serve as instrumental platforms for probing biological phenomena and elucidating intricate cellular mechanisms. These systems afford researchers the opportunity to scrutinize cellular responses within a regulated environment, thereby circumventing the ethical and logistical challenges associated with in vivo experimentation. Three-dimensional (3D) cell cultures have emerged as a viable alternative to mimic in vivo environments. Within this context, spheroids are recognized as one of the most straightforward and efficacious models, presenting a promising substitute for conventional monolayer cultures. The application of 3D cultures of fish cells remains limited, focusing mainly on physiological and morphological characterization studies. However, given the capacity of spheroids to emulate in vivo conditions, researchers are exploring diverse applications of these 3D cultures. These include eco-toxicology, immunology, drug screening, endocrinology, and metabolism studies, employing a variety of cell types such as fibroblasts, hepatocytes, embryonic cells, gonadal cells, gastrointestinal cells, and pituitary cells. This review provides a succinct overview, concentrating on the most frequently employed methods for generating fish cell spheroids and their applications to date. The aim is to compile and highlight the significant contributions of these methods to the field and their potential for future research. [ABSTRACT FROM AUTHOR]

Background Mercury intake is caused by eating seafood, such as tuna and other predatory fish species. To reduce the health risks of mercury intake, it is necessary to continuously measure and monitor mercury concentrations at fish farms and markets. We have developed a compact system that can detect multiple heavy metals by liquid asymmetric-electrode plasma optical emission spectroscopy (LAEP-OES). Objective The validity of the LAEP-OES method for total mercury levels was evaluated using standard solutions, certified substances, and specimens of bluefin tuna and other fish species. Methods All specimens were dissolved in 4 M lithium hydroxide solution and then dispensed into a sample reservoir well of the single-use measurement reagent pack. Total mercury levels were automatically measured within 15 min of placement into the dedicated equipment. A total of 102 fish specimens, classified into 10 fish species, were evaluated using the new method and the results were compared to those obtained from validated analytical methods. Results LOD (0.02 mg/kg), LOQ (0.07 mg/kg), repeatability (4.0%), intermediate precision (9.8%), and trueness (recoveries 107%) of the proposed method were within satisfactory limits for total mercury levels in fish. Additionally, when using various fish species, the method had a strong positive correlation with the results of cold-vapor atomic absorption spectrometry (CV-AAS, the official method) with Spearman rs  = 0.984. Conclusion The LAEP-OES method can be used for measuring total mercury levels in bluefin tuna. Total mercury measurement using this new method has the potential to be applied to other fish species. Highlights Total mercury levels in fish were measured using our unique analysis system. Pacific bluefin tuna, southern bluefin tuna, and Atlantic bluefin tuna distributed in the Japanese market were analyzed for total mercury in their wild and farmed fish varieties. [ABSTRACT FROM AUTHOR]

Fish swimming speed is a standard measurement used for assessing the environment and behavior of fish in aquaculture. However, methods involving propeller-type data loggers, ultrasonic telemetry, and cameras have some limitations. Estimates of swimming speed by cameras are based on swimming trajectories; however, obtaining the swimming trajectories is difficult because the relative positions of the camera and fish body change owing to wave effects. The aim of this study was to describe and present a novel method to estimate the swimming speed of masu salmon (Oncorhynchus masou) influenced by artificially generated waves. Tail-beat frequency was estimated from periodic changes in fish length measured using a stereo camera. The swimming speed was estimated from tail-beat frequency according to the relationship between them as obtained by camera measurement; we found that a fixed stereo camera can help estimate tail-beat frequencies. The estimated data from the moving stereo camera were within the 95% prediction interval of the swimming speed estimation model constructed using the fixed stereo camera. Our study proves the potential of this method in aquaculture. Overall, this approach is a novel method to estimate the swimming speed influenced by wave conditions. In the future, this method can be automated for the identification of abnormal behaviors and detection of malformed fish. [ABSTRACT FROM AUTHOR]

Type III secretion system (T3SS) is an important virulence system in Gram‐negative bacteria. In this investigation, different environmental conditions that regulate the expression of T3SS genes in Yersinia ruckeri were investigated aimed at obtaining a better understanding about its modulation after various environmental challenges. Four isolates of Y. ruckeri CSF007‐82, ATCC29473, A7959‐11 and YRNC10 were cultivated under the diverse in vitro challenges iron depletion, high salt, low pH and in the presence of fish serum or in the fish cell culture (Chinook Salmon Embryo – CHSE). The transcriptional modulation of the chromosomal genes ysaV, ysaC, ysaJ and prgH of ysa were investigated using quantitative real‐time PCR. The expression of prgH, ysaV, ysaC and ysaJ was differentially expressed in all four strains under evaluation. The highest gene expression levels were observed for Y. ruckeri YRNC10 AN after addition of 0.3 M NaCl in Luria Bertani broth. The results obtained from this study provide initial insights into T3SS responses in Y. ruckeri, which pave the way for further studies aimed at expanding our knowledge on the functional roles of the T3SS genes in Y. ruckeri. [ABSTRACT FROM AUTHOR]

Mesopelagic fishes are a vital component of the biological carbon pump and are, to date, largely unexploited. In recent years, there has been an increased interest in harvesting the mesopelagic zone to produce fish feed for aquaculture. However, great uncertainties exist in how the mesopelagic zone interacts with the climate and food webs, presenting a dilemma for policy. Here, we investigate the consequences of potential policies relating to mesopelagic harvest quotas with a dynamic social-ecological modeling approach, combining system dynamics and global sensitivity analyses informed by participatory modeling. Our analyses reveal that, in simulations of mesopelagic fishing scenarios, uncertainties about mesopelagic fish population dynamics have the most pronounced influence on potential outcomes. The analysis also shows that prioritizing the development of the fishing industry over environmental protection would lead to a significantly higher social cost of climate change to society. Given the large uncertainties and the potential large impacts on oceanic carbon sequestration, a precautionary approach to developing mesopelagic fisheries is warranted. [ABSTRACT FROM AUTHOR]

Pisciculture encounters an array of intricate challenges that span disease management, preservation of water quality, prevention of genetic hybridization, ensuring the integrity of net systems, sourcing sustainable aquatic feed, and comprehending fish growth and reproductive dynamics. Addressing these multifaceted challenges necessitates a comprehensive research approach. This study employs an innovative synergy of fuzzy logic and deep learning techniques, resulting in a robust strategy to tackle these obstacles effectively. Fuzzy logic excels in assessing stressed fish conditions by handling inherent uncertainties. Simultaneously, YOLOv7 with fuzzy color enhancement (YOLOv7FCE) is used to detect damaged fish nets, thereby mitigating losses and upholding the integrity of the net infrastructure. This approach also leverages YOLOv7FCE for identifying Cobia fish within shoals, streamlining the identification process. Subsequently, DeepLabv3 is implemented to meticulously segment the recognized Cobia fish, facilitating precise measurements of their physical attributes. This comprehensive methodology yields profound insights into growth patterns and feeding tendencies within the confined aquatic environment. By embracing this approach, the research presents a versatile and adaptive framework that not only enhances our comprehension of piscine dynamics but also holds the potential to revolutionize the aquaculture industry. [ABSTRACT FROM AUTHOR]

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Postharvest and supply chain losses are the main global challenges. The security of future food demand requires certain availability of natural resources and useful application of limited means. This study is based on maximizing the productive use of baren fish farms to meet future food demand. In this work, the simulation optimisation model was used to determine the estimated findings. We developed the life cycle measurement technique to examine the percentage loss occurred during postharvest and supply chain process and the assessment of its economic, environmental and social influences. Results demonstrate the variate average change of postharvest loss and supply chain loss of a farmer, processors, trader, wholesalers and retailers are, respectively, 7.06%, 8.89%, 6.23%, 9.10% and 13.05% regarding sample fish-form as compared to same capacity healthy land fish-form with a productive supply chain operation. The total healthy mud of land and quality water consumed to produce this lost food accumulated 60 thousand hectares and 255 million cubic meters apart from other producing inputs. It is estimated cost $380 million annually 7.8 million tons of growth. The study reveals the significance of better prevention approaches of life cycle waste to reduce the environmental, economic and social impacts. Additionally, it helps to diminish the postharvest loss percentage to decrease the perishability of products throughout the supply chain of aquaculture field and the mechanisms that protect the products until these are sold out to consumers. In order to reduce postharvest losses, the study suggests that farmers be included as supplier actors and measured twice, first at the production stage and then at the supply chain stage. With the use of well-organized techniques, the farmer's education is a key component in reducing postharvest losses of perishable goods and boosting aquaculture sectors. Therefore, sustainable economic growth requires from farmers to supplier and productive coordination in reducing environmental impacts. This could improve their learning, skills and practices towards sustainable growth achievement in perishable products for meaningful use of natural resources. [ABSTRACT FROM AUTHOR]

Estuarine systems that provide valuable ecosystem services to society and important foraging and rearing habitat for fish and wildlife species continue to undergo degradation. In Puget Sound, WA, as much as 70–80% of historic estuarine habitat has been lost to anthropogenic development, and continued losses are expected through the end of the twenty-first century due to rising sea levels. To evaluate whether Puget Sound's estuarine habitats will keep pace with current and projected sea-level rise (SLR), we assessed vertical rates of elevation change from a regional network of surface elevation tables and marker horizons (SET-MH). Over the past two decades, SET-MH equipment has been installed throughout a variety of habitats in five Puget Sound estuaries: the Nisqually, Snohomish, Stillaguamish, and Skagit River estuaries, and Padilla Bay. These data provide a unique opportunity to assess elevation change and habitat resilience across a spatiotemporal and environmental gradient. We observed different rates of surface elevation change among estuaries and habitats (Nisqually = 4.64 ± 2.81 mm/year, Snohomish = 5.71 ± 5.83 mm/year, Stillaguamish = 12.82 ± 10.29 mm/year, Skagit = 16.13 ± 7.57 mm/year, Padilla = − 1.25 ± 1.58 mm/year). The highest rates were found at restoring sites with regular sediment input in the Stillaguamish and Skagit estuaries, whereas rates were consistently negative at low elevation sites in sediment starved Padilla Bay. Many sites in Puget Sound appear to be keeping pace with current rates of relative SLR, and some areas are on track to exceed projected rates through the end of the century. These findings indicate that Puget Sound's estuarine habitats can be resilient to rising tidal levels—as long as sediment delivery is maintained. [ABSTRACT FROM AUTHOR]

The cryopreservation of cell lines such as primordial germ cells and germ cells is a promising strategy to conserve and reconstitute endangered or commercially important species in aquaculture. In Mexico, the northwest region is the center of the country's most significant fishing and aquaculture production. However, most of the species used in capture fishing are overexploited. Despite this, protocols for the cryopreservation of germ cells are non-existent. Therefore, this work aimed to establish a protocol of isolation, identification, and cryopreservation of germ cells in two species, totoaba (Totoaba macdonaldi) and yellowtail amberjack (Seriola lalandi). Three concentrations of trypsin (0.25%, 0.3%, and 0.5%) were tested for gonadal dissociation. The 0.3% trypsin concentration was the best because it presented the most significant number of viable cells, with 14.35 x 105 for totoaba and 2.96 x 105 for yellowtail amberjack. The immunohistochemistry identification of germ cells in both species was positive for vasa, with 33.30% for totoaba and 34.20% for yellowtail amberjack. The cryoprotectant used was ethylene glycol (1.5 M or 2 M). The ideal temperature for the cryopreservation of gonadal tissue was different for each species, -1°C/min for totoaba and -5°C/min for yellowtail amberjack with 58.42% and 63.48% viable cells after thawing, respectively, with ethylene glycol 1.5 M being the best for both species. The non-controlled rate was the most effective technique to freeze the cell suspension, with 4.20 ± 1.09 x 105/mL viable cells for totoaba and 7.31 ± 2.25 x 105/mL for yellowtail amberjack. In conclusion, the results of the isolation, identification, and cryopreservation protocols for germ cells in totoaba and yellowtail amberjack obtained in this work are the first report for fish species from northwest Mexico, opening the door for the generation of cryobanking of germ cells. Finally, this work would help conserve endangered species and be an alternative to conserving species of commercial importance in aquaculture. [ABSTRACT FROM AUTHOR]

ABSTRACT Billions of fishes are kept in captivity for research and food production world‐wide, with a strong impetus for maintaining high welfare standards. Accordingly, the importance of empirical research into the welfare and husbandry of captive fishes is increasingly acknowledged in both science and aquaculture, alongside growing public and governmental interest. Physical enrichment can have an important influence on welfare in of captive fishes, but many questions remain. Here, we summarise the current state of research and outline knowledge gaps in the area of physical enrichment, which is a fundamental aspect to improving welfare of captive fishes. To explore the level of research interest this area across time we conducted a series of surveys, using the number of papers published per year as a metric. These surveys highlight that work on fish welfare, while representing a relatively low proportion of fish research overall, is increasing rapidly. For species that are of aquaculture importance or used commonly as laboratory subjects, we show a positive relationship between general research interest and number of welfare‐related papers. However, for many, particularly relatively less studied, species the proportion of papers on enrichment remains low, with a slower increase compared to welfare‐related papers in general. In terms of common metrics used to quantify fish welfare, there is a reliance on growth and behaviour, with scope for inclusion and combination of a more comprehensive range of reproducible measures. We finish by highlighting recent progress, promising areas for future research and suggestions for advances in this area. [ABSTRACT FROM AUTHOR]

ABSTRACT The objective of this study was to evaluate the effect of dietary supplementation with Citrus sinensis (L.) Osbeck essential oil on the growth, immune system, and resistance to Aeromonas hydrophila infection in Colossoma macropomum fingerlings. The experiment was conducted with five treatments (control diet, Tween80 diet, and diets supplemented with 200, 400, and 800 mg L−1 of C. sinensis essential oil) with four replicates. At the end of the experimental period, growth parameters were measured, and blood samples were collected for thrombogram, leukogram, and phagocytic activity analysis. A bacterial challenge with A. hydrophila was conducted for 96 h. C. macropomum fingerlings that were fed with 400 and 800 mg L−1 of C. sinensis essential oil had the highest growth parameters, with final weights of 533.18 ± 2.03 mg and 531.91 ± 2.67 mg, respectively, and an increase in the number of thrombocytes, lymphocytes, monocytes, and neutrophils, as well as higher phagocytosis rates compared to the control group. Regarding the challenge, fish in the 400 and 800 mg L−1 treatments also exhibited the lowest cumulative mortality rate (26.66% ± 3.33%). Therefore, supplementation with C. sinensis essential oil promotes growth, improves health, and enhances resistance to A. hydrophila in C. macropomum fingerlings. [ABSTRACT FROM AUTHOR]

One of the hallmarks of invasive species is their propensity to spread. Removing an invasive species after establishment is virtually impossible, and so considerable effort is invested in preventing the range expansion of invaders. Silver carp (Hypophthalmichthys molitrix) were discovered in the Mississippi River in 1981 and have spread throughout the basin. Despite their propensity to expand, the 'leading edge' in the Illinois River has stalled south of Chicago and has remained stable for a decade. Studies have indicated that contaminants in the Chicago Area Waterway System (CAWS) may be contributing to the lack of upstream movement, but this hypothesis has not been tested. This study used a laboratory setting to quantify the role of contaminants in deterring upstream movement of silver carp within the CAWS. For this, water was collected from the CAWS near the upstream edge of the distribution and transported to a fish culture facility. Silver carp and one native species were exposed to CAWS water, and activity, behavior, avoidance, and metabolic rates were quantified. Results showed that silver carp experience an elevated metabolic cost in CAWS water, along with reductions in swimming behavior. Together, results indicate a role for components of CAWS water at deterring range expansion. [ABSTRACT FROM AUTHOR]

Background: The biofloc system (BFS) provides a sustainable aquaculture system through its efficient in situ water quality maintenance by the microbial biomass, besides continuous availability of these protein-rich microbes as feed to enhance growth and immunity of the reared organism. This study explores the gill architecture, growth performance, digestive enzyme activity, intestinal microbial composition, and histology of three freshwater fish species, Puntius gonionotus, Pangasianodon hypophthalmus, and Heteropneustus fossilis reared in biofloc based polyculture system. Results: The three species in T2 showed significantly higher WG and SGR, followed by T1 and T3. The wet mount of gill architecture showed smaller inter-filament gaps in gill arches of silver barb followed by stinging catfish and stripped catfish, but showed no correlation with the weight gain. However, silver barb being an omnivore and filter-feeder, accumulated a more diverse microbial community, both in T1 and BFS (T2 and T3), while the bottom feeder H. fossilis exhibited unique gut bacterial adaptability. The presence of floc in T2 and T3 enhanced bacterial abundance in water and fish gut, but their microbial diversities significantly reduced compared to T1 receiving only feed. Next-generation sequencing revealed that the Pseudomonas dominated in gut of P. gonionotus and P. hypophthalmus in T1, Enterobacterales and Fusobacterium prevailed in those of T2 and T3, respectively. In contrast, gut of H. fossilis had the highest proportion of Clostridium in T1, while Rhizobiaceae dominated in T3. Similarly in floc samples, Enterococcus dominated in T1 while Micrococcales and Rhizobiaceae dominated in T2 and T3, respectively. A positive correlation of enterobacteria, with the digestive enzyme activities and growth patterns was observed in all treatments. Conclusion: The present study revealed feeding behaviour to play crucial role in distinguishing the gut microbial composition patterns in fishes reared in Biofloc System. Further it revealed the requirement of supplementary feed along with floc in these three species for higher growth in the biofloc system. [ABSTRACT FROM AUTHOR]

ABSTRACT Haematological and plasma parameters are used in veterinary medicine as a diagnostic tool, allowing for the early detection of potential health and welfare issues. For the implementation of monitoring strategies, reference intervals (RIs) are needed to know when deviations in those parameters become clinically relevant. Here, haematological and plasma biochemical RIs of Norwegian Atlantic salmon (Salmo salar Linnaeus) are presented for 29 biomarkers. Two subgroups were defined from the reference population based on water type, referred to as pre‐adult (freshwater, 166.8 ± 118.4 g, N = 979) and adult (seawater, 2655 ± 2883 g, N = 4941), collected at 93 fish farms along the Norwegian coast. While the influence of various pre‐analytical variables on RIs is well documented, aquaculture practitioners cannot always control those variables in the field. Here, RIs were calculated from blood samples collected based on local pre‐analytical practices and then further processed under standardised conditions (analytical phase). RIs are therefore considered highly relevant for the application in the field. Finally, when taking blood samples in the field, it is advised to centrifuge whole blood as soon as possible, while plasma parameters investigated were stable for 168 h at 4°C or 72 h at room temperature. [ABSTRACT FROM AUTHOR]

ABSTRACT Chemokines play a crucial role in immune responses by facilitating the migration of cells expressing corresponding chemokine receptors along concentration gradients. Photobacterium damselae subsp. Damselae (PDD) and Nocardia seriolae (NS) are known to induce substantial mortality in silver pomfret populations, yet there exists a dearth of research regarding the immune response of CCLs in PDD‐ or NS‐infected silver pomfret. In our investigation, we identified 10 PaCCLs, which include one fish‐specific CCL (PaCCL44). Phylogenetic analysis revealed considerable diversity in CCL types and copy numbers among various teleost fishes. Notably, silver pomfret lacks specific CCL genes, with most PaCCLs exhibiting heightened expression levels in immune‐related organs such as the spleen and kidney, and some being expressed in mucosal immune‐related organs like the skin and gills. Transcriptome analysis conducted on silver pomfret infected with NS and PDD elucidated that the expression changes of PaCCLs primarily manifested in the spleen during the initial stages of NS infection, shifting to the kidney in later stages. Conversely, the expression changes of PaCCLs following PDD infection predominantly occurred in the kidney. In vitro studies using silver pomfret spleen cell lines demonstrated an early peak in PaCCLs expression during infection, followed by gradual decline with NS treatment and rapid diminishment with PDD treatment. These findings suggest that PaCCLs primarily support the innate immunity of silver pomfret, potentially exhibiting chemotactic effects in the early infection stages, such as the synergistic action of PaCCL4 and PaCCL25, and later serving as direct antibacterial agents. NS invasion is characterised by a chronic infection affecting multiple organs, whereas PDD primarily inflicts severe damage to the kidney. PaCCL19a and PaCCL19b are specific to PDD, and their expression levels may decrease in the later stages of infection due to PDD immune escape. These data offer initial insights into understanding the mechanism underlying the innate immune response of the CCL gene family in silver pomfret and provide theoretical underpinnings for fish culture practices. [ABSTRACT FROM AUTHOR]

Feed costs constitute a significant part of the expenses in the aquaculture industry. However, feeding practices in fish farming often rely on the breeder's experience, leading to feed wastage and environmental pollution. To achieve precision in feeding, it is crucial to adjust the feed according to the fish's feeding state. Existing computer vision-based methods for assessing feeding intensity are limited by their dependence on a single spatial feature and manual threshold setting for determining feeding status constraints. These models lack practicality due to their specificity to certain scenarios and objectives. To address these limitations, we propose an integrated approach that combines computer vision technology with a Convolutional Neural Net-work (CNN) to assess the feeding intensity of farmed fish. Our method incorporates temporal, spatial, and data statistical features to provide a comprehensive evaluation of feeding intensity. Using computer vision techniques, we preprocessed feeding images of pearl gentian grouper, extracting temporal features through optical flow, spatial features via binarization, and statistical features using the gray-level co-occurrence matrix. These features are input into their respective specific feature discrimination networks, and the classification results of the three networks are fused to construct a three-stream network for feeding intensity discrimination. The results of our proposed three-stream network achieved an impressive accuracy of 99.3% in distinguishing feeding intensity. The model accurately categorizes feeding states into none, weak, and strong, providing a scientific basis for intelligent fish feeding in aquaculture. This advancement holds promise for promoting sustainable industry development by minimizing feed wastage and optimizing environmental impact. [ABSTRACT FROM AUTHOR]

An adequate understanding of fish behaviors and their interaction with farmspecific environments is pivotal for enhancing fish welfare in aquaculture. The fair-fish database aims to provide a consistent overview of the welfare of farmed fish. This platform consolidates ethological knowledge into profiles of farmed aquatic species. Its WelfareCheck profiles are organized around welfare indicators, with each criterion receiving classifications (no findings, unclear, low, medium, and high) regarding the likelihood and potential for individuals of a given species to experience good welfare in aquaculture systems, along with the associated certainty level. These criteria include home range, depth range, migration patterns, reproduction, aggregation patterns, aggressive behavior, substrate needs, stress responses, malformations, and slaughtering protocols. We investigated which of these 10 criteria are most relevant to the overall welfare of a species, considering the likelihood, potential, and certainty of good welfare in aquaculture. To achieve this, we reviewed and recorded the high classifications across each criterion and dimension from all published WelfareCheck profiles. To further investigate knowledge gaps across the criteria, we also recorded classifications marked as unclear and no findings. These were then compared across the criteria to assess the frequency of such classifications. While no significant differences were found between the criteria regarding the likelihood that the surveyed species meet their basic welfare needs, criteria related to reproduction, slaughter practices, and substrate needs demonstrated a high potential for better welfare outcomes. Moreover, reproduction and migration patterns exhibited high certainty in the available literature. Based on these findings, we conclude that improving the reproduction of farmed aquatic species, considering their natural needs and behavior, could be an effective and reliable approach to improving welfare. However, we also found a low certainty of information on aggression and an absence or conflicting data on home range, aggregation patterns, stress, and malformations. This highlights an urgent need for research in these areas, which are fundamental for developing more accurate assessments and recommendations for farmed aquatic species. [ABSTRACT FROM AUTHOR]

Sex identification and the selection of monosex male tilapia are crucial for tilapia aquaculture. In this study, we evaluated the application of ultrasonography as an alternative procedure for sex identification and reproductive assessment in Nile tilapia (Oreochromis niloticus). Ultrasonography was performed on 23 fish weighing 232-1,281 g to capture longitudinal and transverse images of the ovaries and testes. Female tilapia were identified by the presence of numerous small egg granules and gray or light gray ovarian tissue and male tilapia by the homogeneous echogenicity and uniform gray tubular appearance of the testes. These distinct echogenic patterns allowed for accurate differentiation between the female and male fish. Ultrasonography achieved a 95% accuracy in sex identification, with minimal stress to the fish during the procedure, compared to manual sex sorting, which demonstrated an accuracy of 87%. Furthermore, the method facilitated the assessment of the reproductive status of the fish, including the maturation stages and fecundity potential. The use of ultrasonography offers significant advantages over traditional methods, such as animal welfare enhancements and improved breeding program efficiency. Our findings support the integration of ultrasonography into aquaculture practices and will promote sustainable and humane fish farming while optimizing reproductive management and productivity. [ABSTRACT FROM AUTHOR]

We review literature on the displacement paradox and the Jevons paradox, with consideration of their implications for the potential effects of aquaculture on wild fisheries. The Jevons paradox refers to circumstances where improvements in the efficiency of resource use lead to growth in consumption and therefore undermine conservation. The displacement paradox refers to circumstances where increasing use of a potential substitute for a resource (e.g., farmed fish) does not lead to proportionate reduction in consumption of the other resource (e.g., wild fish). The literature on the displacement paradox and the Jevons paradox suggests that there may be unanticipated consequences from the rise of aquaculture that may be detrimental for fisheries conservation. Here, we present theoretical explanations, drawing on the tragedy of the commodity, for understanding the tendencies for these technological paradoxes to occur and emphasize their relevance for concerns associated with fisheries and aquaculture systems. [ABSTRACT FROM AUTHOR]

Background: Aquaculture, traditionally a form of biotechnology, has evolved to integrate innovative biotechnological applications, such as advanced feed formulations, aimed at improving the growth performance and health of farmed fish species. In the present study, the effects of feeding rainbow trout with novel feed formulations were investigated. Fish growth, gut and liver morphology, the concentration of fatty acids in the fillet, and volatile fatty acids in the gut were assessed. The study also validated scenarios from in vivo experiments using a nutrient-based model called FEEDNETICS™. This globally used model serves as a tool for data interpretation and decision support in the context of precision fish farming. Methods: Alternative protein and oil sources, including poultry by-product meal (PBM) and natural algae oil, were explored as sustainable replacements for fishmeal (FM) and fish oil (FO). A 90-day feeding trial was conducted using rainbow trout, comparing two isoproteic, isolipidic and isoenergetic diets. The control diet contained 15% FM, 5% PBM, and 8% FO, while the test diet replaced FM with 15% PBM and 5% feather meal hydrolysate (FMH), and fully substituted FO with VeraMaris® natural algae oil and rapeseed oil. Results: PBM successfully replaced FM protein without negatively affecting feed intake, growth performance or feed utilization in trout. The combination of PBM and natural algae oil was well tolerated by the trout and showed no negative effects on gut health. A detailed analysis of fatty acids in the fillet revealed that PUFAs of the n3 and n6 series were significantly higher in the PBM group than in the FM group. Values of fatty acid-related health indexes, including atherogenicity index, and thrombogenicity index, confirmed the high nutritional value of trout filet, thus representing a healthy product for human. In addition, the predictions using the FEEDNETICS™ indicated that the tested novel alternative formulations are economically viable. The validation of the model for fish growth resulted in a Mean Absolute Percentage Error (MAPE) of 8%. Conclusions: The FEEDNETICS™ application enhances our ability to optimize feeding strategies and improve production efficiency in the aquaculture industry. VeraMaris® algae oil and PBM could serve as viable and sustainable raw materials for fish feed, promoting environmentally friendly aquaculture practices. [ABSTRACT FROM AUTHOR]

The use of nutraceuticals in aquaculture is getting attention to minimize oxidative stress and increase immunity of aquatic animals. In our experiment, we tested the potency of Phyllanthus niruri, as a stress-reducing and immune-stimulating agent in Nile tilapia, Oreochromis niloticus. We reared fish in a recirculating system for 90 days at low (5 g/L) and high (30 g/L) densities. We fed half of the low and high-density fish with commercial feed (control feed) and the other half, with 5% Phyllanthus niruri incorporated into commercial feed (supplemented feed). We assessed plasma cortisol, blood glucose, packed cell volume, plasma proteins, phagocytic capacity, respiratory burst activity, and lysozyme activity. None of these parameters showed any significant difference among the experimental groups. Based on our findings, we conclude that Phyllanthus niruri does not have any potential role in modulating stress and immune response in fish as a nutraceutical. [ABSTRACT FROM AUTHOR]

ABSTRACT Recent years have witnessed a remarkable global surge in fish production, with Nile tilapia (Oreochromis niloticus) emerging as a prominent contributor owing to its high demand as a nutritious food source. However, unlike terrestrial species, maintaining genealogical control and collecting phenotypic data in fish farming poses significant challenges, necessitating advancements to support genetic improvement programmes. While conventional methods, such as body measurements using rulers and photographs are prevalent in data collection, the potential of ultrasound—a less invasive and efficient tool for fish measurement—remains underexplored. This study assesses the viability of ultrasonography for genetically selecting carcass characteristics in Nile tilapia. The investigation encompasses data from 897 animals representing 53 full‐sib tilapia families maintained in the genetic improvement programme at the Federal University of Lavras. To measure carcass traits, the animals were sedated with benzocaine and ultrasound images were obtained at three distinct points. Subsequently, the animals were euthanised through medullary sectioning for further carcass processing. After evisceration, filleting and skinning, all weights were meticulously recorded. (Co)variance components and genetic parameters of the measured traits were estimated using the Bayesian approach by Gibbs sampling implemented in MTGSAM (Multiple Trait Gibbs Sampling in Animal Models) software. Heritabilities estimated for the studied carcass traits were moderate, ranging from 0.23 to 0.33. Notably, phenotypes derived from ultrasound images demonstrated substantial genetic correlations with fillet yield (0.83–0.92). In conclusion, this study confirms that indirect selection based on ultrasound images is effective and holds promise for integration into tilapia breeding programmes aimed at enhancing carcass yield. [ABSTRACT FROM AUTHOR]

Simple Summary: This experiment was conducted in accordance with the prevailing trend of identifying alternative sources of nutrition to compensate for the economic shortcomings of fish meal in the aquaculture industry. The experiment employed soybean-based concentrated protein, which is approximately half the cost of fish meal, and focused on investigating its impact on growth and physiological processes. Three experimental diets were prepared: the control diet (Con) contained 60% FM, and the experimental diets contained 25% (SPC25) and 50% (SPC50) FM replaced by SPC. Following the 140-day feeding period, no significant differences in growth performance were observed. However, an increase in the replacement rate was associated with a reduction in stress and immune sensitivity, while the SPC25 treatment exhibited elevated levels of digestive enzyme-related genes. Therefore, substituting 25% FM with SPC was most effective for commercial fish farming. This study identified the effects of substituting fishmeal (FM) with soy protein concentrate (SPC) supplemented with lysine and methionine in the olive flounder (Paralichthys olivaceus) diet on the expression of genes related to growth, stress, immunity, and digestion. Three experimental diets were prepared; the control diet (Con) contained 60% FM, and the experimental diets contained 25% (SPC25) and 50% (SPC50) FM replaced by SPC. After the 140-day feeding period, weight gain, specific growth rate, feed availability, biological indices, and chemical composition of the muscle were not significantly affected by the dietary treatments. The gene expression levels of growth-related genes (IGF, GFB-3), immune-related genes (IL-8 and caspase), and stress-related genes (SOD, GPX, PRX, TRX) were higher in Con fish than in those fed the SPC25 and SPC50 diets. Chymo-TRY2, TRY2, and TRY3 in the stomach of fish fed the SPC25 diet were higher than fish fed the Con or SPC50 diets. TRY2 and lipase of fish fed the SPC25 diet were higher than those of fish fed the other diets but TRY3 was not significantly affected by the treatments in the intestine. In conclusion, substituting 25% FM with SPC was the most effective diet for the expression of growth, immune, stress, and digestive enzyme genes. [ABSTRACT FROM AUTHOR]

Simple Summary: The current state of rainbow trout, Oncorhynchus mykiss, was investigated 50 years after the first introduction of the species to the water bodies of the Balkhash basin. The wild form of the species from Kamchatka and the cultured form from European fish farms have successfully adapted to the local environmental conditions. Unlike in most other regions of the world, rainbow trout have not spread beyond the water bodies of their original introduction and have not significantly impacted native fish diversity. Rainbow trout, or mykiss (Oncorhynchus mykiss), is one of the most popular species used in aquaculture and has been naturalized worldwide, including in the Central Asian Balkhash basin, which has unique aboriginal fish fauna. Both rainbow trout from European farms and wild mykiss from Kamchatka were introduced to some mountain lakes and rivers of the Balkhash basin about 50 years ago. This study investigates the current distribution and life history traits of the alien species and its possible impact on the local fish fauna. This study showed that the rainbow trout occupies various habitats in the Ili River basin: mountain lakes, fast-flowing mountain rivers, and lowland rivers with slow currents and warm water (up to +27 °C). Rainbow trout from European fish farms dominate the mountain Middle Kolsay Lake, while the wild trout from Kamchatka occupies the small Ulken Kokpak River. Both co-occur in the Chilik River. Contrary to that in other regions, the distribution of rainbow trout in the Balkhash basin remained almost the same after their introduction. Broad intrapopulation variability in terms of size, growth rate, and maturation age was revealed, apparently as a result of adaptation to the new environment and intrapopulation competition. In particular, the growth rate has decreased, but life span, surprisingly, has increased as compared to the originally introduced fish. Intrapopulation variation in growth and maturity patterns was also noted. Differences in skin coloration between highland (cold-water) and lowland (warm-water) populations were discovered. The feeding mode of naturalized trout is insectivorous (insect imago), indicating that it occupies its own niche in the local fish communities. The largest population of rainbow trout was recorded in the Lower Kolsay Lake, lowering the population of native fish species, while in other localities, no negative impact on local fish communities was recorded. [ABSTRACT FROM AUTHOR]

Simple Summary: Identification and counting of fish are relevant tools for managing the stocking, harvesting, and marketing of farmed fish. Researchers have used convolutional networks for these purposes and employed various approaches to improve network learning. Batch normalization is one technique that enhances network stability and accuracy. The study aimed to evaluate machine learning for identifying and counting pirapitinga Piaractus brachypomus fry with different batch sizes. The researchers used one thousand photographic images of Pirapitinga fingerlings, labeled with bounding boxes. They trained the adapted convolutional network model with batch normalization layers inserted at the end of each convolution block. The training involved one hundred and fifty epochs, with batch sizes for normalization set to 5, 10, and 20. Identifying and counting fish are crucial for managing stocking, harvesting, and marketing of farmed fish. Researchers have used convolutional networks for these tasks and explored various approaches to enhance network learning. Batch normalization is one technique that improves network stability and accuracy. This study aimed to evaluate machine learning for identifying and counting pirapitinga Piaractus brachypomus fry with different batch sizes. The researchers used one thousand photographic images of Pirapitinga fingerlings, labeled with bounding boxes. They trained the adapted convolutional network model with batch normalization layers added at the end of each convolution block. They set the training to one hundred and fifty epochs and tested batch sizes of 5, 10, and 20. Furthermore, they measured network performance using precision, recall, and mAP@0.5. Models with smaller batch sizes performed less effectively. The training with a batch size of 20 achieved the best performance, with a precision of 96.74%, recall of 95.48%, mAP@0.5 of 97.08%, and accuracy of 98%. This indicates that larger batch sizes improve accuracy in detecting and counting pirapitinga fry across different fish densities. [ABSTRACT FROM AUTHOR]

Simple Summary: Fish farming provides an efficient means of obtaining high-quality protein for humans. However, the decreased growth rate of aquaculture fish due to germplasm degradation often increases production costs and reduces economic benefits. Therefore, it is particularly important to develop fast-growing varieties and elucidate the genetic mechanisms underlying growth traits. In this study, we identified 50 growth-related markers in the genome of Lateolabrax maculatus, an important marine aquaculture species, with the phenotypic variance explained up to 15.82%, which will help in marker-assisted breeding for fast-growing varieties. Additionally, 47 growth-related candidate genes were annotated, and the functions of some of these genes in growth traits have been confirmed in mice or zebrafish through gene knockout or knockdown experiments. The 47 candidate genes are mainly associated with the metabolism of energy, glucose, and lipids and the development of musculoskeletal and nervous systems, which may act as drivers for the growth of L. maculatus. Altogether, our study identified growth-related markers and candidate genes, which will help develop the fast-growing varieties of L. maculatus and elucidate genetic mechanisms underlying its growth traits. Spotted sea bass (Lateolabrax maculatus) is an important marine economic fish in China, ranking third in annual production among marine fish. However, a declined growth rate caused by germplasm degradation has severely increased production costs and reduced economic benefits. There is an urgent need to develop the fast-growing varieties of L. maculatus and elucidate the genetic mechanisms underlying growth traits. Here, whole-genome resequencing technology combined with extreme phenotype genome-wide association analysis (XP-GWAS) was used to identify candidate markers and genes associated with growth traits in L. maculatus. Two groups of L. maculatus, consisting of 100 fast-growing and 100 slow-growing individuals with significant differences in body weight, body length, and carcass weight, underwent whole-genome resequencing. A total of 4,528,936 high-quality single nucleotide polymorphisms (SNPs) were used for XP-GWAS. These SNPs were evenly distributed across all chromosomes without large gaps, and the average distance between SNPs was only 175.8 bp. XP-GWAS based on the Bayesian-information and Linkage-disequilibrium Iteratively Nested Keyway (Blink) and Fixed and random model Circulating Probability Unification (FarmCPU) identified 50 growth-related markers, of which 17 were related to body length, 19 to body weight, and 23 to carcass weight. The highest phenotypic variance explained (PVE) reached 15.82%. Furthermore, significant differences were observed in body weight, body length, and carcass weight among individuals with different genotypes. For example, there were highly significant differences in body weight among individuals with different genotypes for four SNPs located on chromosome 16: chr16:13133726, chr16:13209537, chr16:14468078, and chr16:18537358. Additionally, 47 growth-associated genes were annotated. These genes are mainly related to the metabolism of energy, glucose, and lipids and the development of musculoskeletal and nervous systems, which may regulate the growth of L. maculatus. Our study identified growth-related markers and candidate genes, which will help to develop the fast-growing varieties of L. maculatus through marker-assisted breeding and elucidate the genetic mechanisms underlying the growth traits. [ABSTRACT FROM AUTHOR]

Simple Summary: Aquaculture production has recently surpassed wild fish capture, a growth largely driven by the intensification of fish farming. However, this rapid expansion increases the risk of disease outbreaks and impairs growth performance. These adverse effects can be mitigated through the use of functional additives, such as minerals, vitamins, and industry byproducts with immunomodulatory properties. In this context, we evaluated the effects of functional diets supplemented with vitamins C and E, zinc, and orange peel fragments on the health status and growth performance of juvenile Nile tilapia under stress conditions. The results of this study showed that orange peel fragments, in combination with vitamins C and E, and zinc, produced synergic effects on the immune and antioxidant responses of Nile tilapia subjected to stress. These findings suggest that this supplementation could be an effective nutritional strategy to mitigate the adverse effects of intensive fish farming. This study aimed to evaluate the effect of dietary orange peel fragments (OPFs) enriched with vitamins C (C) and E (E), as well as zinc (Zn) on the growth performance, hematological profile, immunological parameters, antioxidant capacity, and fillet lipid peroxidation of Nile tilapia subjected to heat/dissolved oxygen-induced stress (HDOIS), transport-induced stress (TIS), and Aeromonas hydrophila infection (BC). A group of 500 male Nile tilapia (2.7 ± 0.03 g) was randomly distributed in twenty-five 250 L aquaria (20 fish/aquarium) and fed diets containing OPFs (6 g kg−1), OPFs/C (6 g kg−1/1.8 g kg−1), OPFs/E (6 g kg−1/0.4 g kg−1), OPFs/Zn (6 g kg−1/0.21 g kg−1), or OPFs/C/E/Zn (6 g kg−1/1.8 g kg−1/0.4 g kg−1/0.21 g kg−1) for 100 days. The diets were formulated to contain 30% crude protein and 17 MJ kg−1 gross energy. After the feeding period, three groups of fish were independently subjected to a different type of stress: HDOIS (34 °C) for two days; TIS for four hours, or BC for 15 days. The hematological profile, antioxidant capacity, and fillet lipid peroxidation were determined before and after all the stress treatments, along with immunological parameters, which were investigated only for the fish subjected to bacterial infection. In summary, the results showed that growth was not affected by the OPFs, nor by the OPFs enriched with C, E, and Zn; bacterial infection determined anemia for the fish fed any of the experimental diets; the OPFs did not prevent lipid peroxidation under TIS and BC; on the other hand, when enriched with C/E/Zn, lipid peroxidation decreased under HDOIS and TIS. In conclusion, the OPFs enriched with C/E/Zn showed a synergistic effect that promoted an increase in antioxidant enzyme activity, a decrease in lipid peroxidation, and the maintenance of the hematological profile under HDOIS and TIS, but they were not able to maintain the health status under BC. [ABSTRACT FROM AUTHOR]

Salinity adaptation is an important issue in aquaculture. Understanding the immediate-early response to salinity stress helps in comprehending this process. In vitro experiments using cell lines can explain cell-independent reactions without the involvement of hormones in vivo. In this study, salinity stress experiments were conducted using cell line derived from the gills of Gymnocypris przewalskii (GPG cell line) to isolate immediate-early response-related genes and miRNAs using transcriptomics, followed by bioinformatics analysis. The results showed that intracellular free Ca2+ appeared to be a key factor in cell sensing and initiating downstream cell signaling in response to external salinity. Additionally, cell apoptosis was the most common feature of salinity stress, with multiple signaling pathways involved in salinity-induced cell apoptosis. Furthermore, MiRNAs played a crucial role in the rapid response to salinity stress by selectively inhibiting the expression of specific genes. Additionally, for the first time in the G. przewalskii genome, Tf2 and TY3 families of transposons were found to have responsive roles to the external salinity stress. This study contributes to a better understanding of osmotic sensing in G. przewalskii and provides theoretical assistance for improving salinity adaptation in aquaculture fish species. [ABSTRACT FROM AUTHOR]

Background: Streptococcus agalactiae (Group B streptococcus, GBS) induces a serious infection that can harm not only aquatic life but also humans and other animals. In a fish farm in southern Egypt, Nile tilapia (Oreochromis niloticus) has developed an epidemic with clinical symptoms resembling piscine streptococcosis. Results: Initial microscopic inspection of the affected fish brain and kidney indicated the presence of Gram-positive cocci. S. agalactiae was effectively isolated and identified using nucleotide homology of the 16S rRNA and species-specific PCR. The partial 16S rRNA sequence was deposited in the GenBank database at the NCBI and given the accession number MW599202. Genotyping using RAPD analysis indicated that the isolates in the present study belonged to the same genotypes and had the same origin. The challenge test, via immersion (9.2 × 107, 9.2 × 106, and 9.2 × 105 CFU/ml for 1 h) or intraperitoneal injection (4.6 × 107, 4.6 × 106, and 4.6 × 105 CFU/fish), elicited clinical symptoms resembling those of naturally infected fish with a mortality rate as high as 80%. The ability to create a biofilm as one of the pathogen virulence factors was verified. Zinc oxide nanoparticles and the ethanolic leaf extracts of nine medicinal plants demonstrated considerable antibacterial activities against the tested S. agalactiae strain with low minimum bactericidal concentrations (MBC) and minimum inhibitory concentrations (MIC). The ethanolic leaf extracts from Lantana camara and Aberia caffra showed potent antibacterial activity with MBC values of 0.24 and 0.485 mg/ml, and MIC values of 0.12 & 0.24 mg/ml, respectively. Conclusion: This study isolated S. agalactiae from O. niloticus mortalities in a fish farm in Assiut, Egypt. The pathogen persists in fish environments and can escape through biofilm formation, suggesting it cannot be easily eliminated. However, promising findings were obtained with in vitro control employing zinc oxide nanoparticles and medicinal plant extracts. Nevertheless further in vivo research is needed. [ABSTRACT FROM AUTHOR]

ABSTRACT Natural feed additives of plant/animal/microbial origin are researched as supplements in aquaculture to improve the properties of feed, minimize the usage of chemical alternatives, reduce food safety risks and ensure sustainability to combat global food and nutritional security. Side streams generated during shellfish processing possess valuable ingredients: protein, lipids, carotenoids, minerals and chitins. Considering the current trend of organic farming and antibiotic‐free fish and shellfish, crustacean processing side streams and their derivatives seem promising and emerging resources as natural additives/supplements for formulating high‐quality feeds with superior benefits. Lower concentrations of chitin and chitosan in diets are reported to stimulate the growth of shellfish and finfish under controlled conditions. Oligomers of chitosan and nano‐chitosan are also the other potential derivatives as natural supplements in feed for better growth performance of aquaculture varieties. This review focuses on the significance of crustacean processing side streams and their derivatives, especially shrimp head meal, chitin, chitosan and chitosan oligosaccharides as potential natural additives in aquafeeds for promoting the growth performance of cultured fin fishes and shell fishes. Utilization in aquafeeds and the development of natural value‐added supplements from crustacean processing side streams, especially shrimp head and shell leftover, offer an answer to the negative environmental impact due to its dumping; reduce the dependency on food fish for fish meal production & fishmeal for aquafeeds; solution to maintain the economic viability of the fish farmers & industry as well as to ensure the supply of safer and healthy aquatic foods to meet the objectives of sustainable development goals. [ABSTRACT FROM AUTHOR]

Biofloc technology offers a viable choice for the rearing of fish seed by offering a safe and protected habitat for young fish. Nevertheless, it is crucial to establish a standardised stocking density and implement effective ameliorative steps in order to successfully utilise this technology. In this study, a 90‐day investigation was conducted to assess the effect of stocking density and dietary vitamin C (Vit C) levels on the growth and immunity of Labeo gonius fry (1.03 ± 0.01 g) reared in a biofloc system. Three stocking density groups (5, 10 and 15 fish per 50 L) were established, and each experimental group was supplemented with three levels of Vit C (0, 500 and 1000 mg kg−1). The highest survival rate was observed in the lowest density group (five fish per 50 L) fed with 1000 mg kg−1 Vit C. A better feed conversion ratio and significantly higher protein efficiency ratio were found in the moderate stocking density group (10 fish per 50 L) fed with 500 mg kg−1 Vit C. Total leukocyte count (TLC), haemoglobin, and packed cell volume improved in Vit C‐fed groups. The total erythrocyte count (TEC) increased in groups fed Vit C and stocked at lower densities (5 and 10 fish per 50 L). Total serum protein (TPP) content increased when Vit C was added at a rate of 500 mg kg−1. Serum glucose and cortisol levels were significantly reduced in Vit C‐supplemented groups. Supplementation of Vit C at 500 mg kg−1 resulted in a significantly lower value of malondialdehyde (MDA). Thus, the findings confirm that the incorporation of Vit C in the basal diet promotes the growth and health status of L. gonius fry reared in the biofloc system at high‐density rearing. [ABSTRACT FROM AUTHOR]

With the development of cage culture, increasing heavy metals concentrations are being taken into sediments. The accumulation of heavy metals in sediments may cause long term environmental issues and pose threat to human health. Fourteen surface sediment samples were collected to assess the contamination status and potential ecological risk of heavy metals, and identify their potential sources from the cage fish farm of Poyang Lake. The concentrations of Cu, Pb, Zn, Cd, Cr, As and Ni in the sediments were measured by ICP-MS. The geo-accumulation index, enrichment factor and potential ecological risk index were implied to evaluate their pollution levels and ecological risk. The principal component analysis was used to identify their potential sources. The results showed that all of the examined heavy metals content exceeded their background values. These heavy metals (except Cd, Cr and As) presented moderately polluted level. Cu showed significant enrichment, Zn, Pb and Ni exhibited moderate enrichment, As and Cd presented minimal enrichment. Cu and Cd posed a moderate ecological risk, and the other heavy metals posed a low ecological risk. The comprehensive potential ecological risk was associated with considerable ecological risk. Cage culture, smelting, mining and agriculture activities were their primary pollution sources. [ABSTRACT FROM AUTHOR]

Steroid hormones, recognized as emerging environmental contaminants, have garnered increasing attention in recent years. The present work studied the distribution characteristics in the environment, bioaccumulation in aquatic products, and the associated environmental and health risks of typical steroid hormones from commercial freshwater aquaculture farms operating under different aquaculture modes (monoculture and polyculture). Totals of 9 and 14 steroid hormones were detected in water and sediment samples, with concentrations ranging from 0.66 ± 0.17 ng/L to 40.5 ± 5.08 ng/L and from 0.36 ± 0.08 ng/g to 123 ± 19.9 ng/g, respectively. Hazard index (HI) calculations indicated that all sampling locations were identified as medium or high risk for both water and sediment matrices. Nineteen steroids were detected in at least one type of tissue, with the concentrations in the bile, plasma, muscle, liver, and gill ranging from 5000 L/kg). Notably, despite low estimated daily intakes (EDIs) (0.43–6.43 ng/day/person to 18.7 ng/day/person) and hazard quotients (HQs) (below 4.188 × 10−7), the high bioaccumulation factors (BAFs) underscore the necessity for stringent regulatory measures by local governments. Additionally, a comparison of EDI results across different aquaculture modes and fish species revealed that steroid hormone-related health risks to humans are influenced by both the fish species and the aquaculture mode. This study indicated that the consumption of poly-cultured fish (e.g., bighead carp) may pose a greater steroid-related health risk, compared to the consumption of mono-cultured fish. [ABSTRACT FROM AUTHOR]

Background: Recirculating aquaculture systems can cause chronic stress in fish when stocking density is too high. However, this study tested whether low stocking density can cause fish stress. Adult rainbow trout, with an average weight of 1.517 kg (± 0.39), were subjected to low (12 kg/m3 ± 0.94) and moderate (43 kg/m3 ± 2.03) stocking densities for 24 days in a recirculating system maintained at 15 °C. At the end of the experiment, fecal microbiome analysis was carried out using a 16S rRNA amplicon sequencing. Additionally, an untargeted plasma metabolomics analysis was conducted. Results: The moderate stocking density group harboured greater numbers of commensals, such as C. somerae, R. lituseburensis, and L. plantarum. In contrast, detrimental species such as S. putrifacens and P. putida were abundant in the low-stocking density fish. Functional microbiome profiling revealed vitamin B12 salvage and synthesis in moderate stocking densities, which may support intestinal tight junction function. Additionally, vitamin B1 biosynthesis pathways were more abundant in the moderate stocking density group, which may function towards oxidative energy metabolism and protect against oxidative stress. A complementary plasma metabolomics study, although done at slightly different stocking densities and duration, confirmed the presence of blood metabolic stress markers. Elevated levels of L-lactic acid and L-Norvaline, L-Valine, and L-glutamine, indicate low stocking density fish were under stress. Furthermore, a P4HA2 stress gene biomarker confirmed the occurrence of stress in low-density fish. This study suggests that low stocking density can induce stress in fish. Moreover, moderate stocking density leads to a distinct and beneficial fecal microbiome profile. Conclusion: Our study highlights the potential benefits of optimizing the stocking density of fish in recirculating aquaculture systems. This can improve fish health and welfare, promoting a more resilient fecal microbiome. [ABSTRACT FROM AUTHOR]

AbstractThe diversification of modern aquaculture systems with high-value finfish species, including Percidae, is hampered by various diseases or even epidemics caused by a wide range of viruses, bacteria, fungi and parasites. The present meta-analysis revealed six viral, four fungal, and 30 bacterial families as the dominant threats to percid aquaculture, in addition to a broad and diverse list of 91 aquatic parasite families. Understanding the multi-faceted interactions between the percid host and diverse pathogens paves the way for effective health concepts in aquaculture. In the past decades, both general and percid-specific immune defence mechanisms have been elucidated that mitigate the invasion and pathogenicity of harmful microorganisms and parasites. Some of these immune parameters offer valuable approaches to optimize the current farming of percid fishes, which is still dominated by conventional pharmaceuticals, whereas immunostimulatory feed additives or vaccination strategies remain rarely used. Another efficient and sustainable way to combat common diseases in aquaculture is through selective breeding, but selective breeding programs for percids are not yet in operation. This review identifies existing knowledge gaps regarding immune modulation in percids and suggests approaches to increase their immunocompetence. The variety of criteria suggested here may be incorporated into modern healthcare concepts for percid fishes to ensure adaptation to societal and food production demands. [ABSTRACT FROM AUTHOR]

The use of antimicrobials is essential for the aquaculture sector; however, their misuse is cause for concern because it could adversely affect the environment and human health. Irresponsible use of antimicrobials can lead to antimicrobial resistance and result in the presence of unwanted residues in aquaculture products. The establishment of maximum residue limits (MRLs) for antimicrobials is of great importance for monitoring their correct use, but the lack of harmonized standards as well as the regulatory gaps for the aquatic products create a challenging situation, as it is reflected in import notifications related to food safety. This paper collects information about current MRLs for antimicrobials in aquatic commodities in the main importing and exporting countries of aquatic products and compares them with each other and with MRLs set by Codex Alimentarius. This analysis highlighted the need for Codex Alimentarius guidance regarding MRLs for nine antimicrobials in aquaculture products (chlortetracycline, doxycycline, enrofloxacin, erythromycin, florfenicol, sulfadimethoxine + ormetoprim, sulfamerazine, tetracycline, and trimethoprim). This paper shows that there is still work to do to implement exhaustive science‐based international standards for residues permitted in aquatic commodities and promote harmonization. [ABSTRACT FROM AUTHOR]

Background: Hypoxia stress resulted in mortality during the fish aquaculture program, affecting the sustainable development of the aquaculture industry. The Egyptian strain of O. niloticus showed a strong ability to hypoxia. In this study, a Nile tilapia strain that was kept and selected for 45 years by the author's team was used to elucidate the mechanism of the hypoxia response in the liver, including the identification of metabolic pathways and genes, involved in the hypoxia response of this strain. Results: The effects of hypoxia stress were detected at 0-hour, 6-hour, and 72-hour time points (0 h, 6 h, 72 h) on tilapia liver at 1 mg/L dissolved oxygen conditions. The blood triglyceride, blood glucose and cholesterol values exhibited significantly different change trends, but the hemoglobin content showed no significant differences between 0 h, 6 h and 72 h (P > 0.05). The activities of catalase (CAT), glutathione peroxidase (GSH-PX), total antioxidant capacity (T-AOC), lactate dehydrogenase (LDH), and acid phosphatase (ACP) in the liver tissue gradually increased at 0 h, 6 h and 72 h (P < 0.05). Histological analyses revealed structural changes in intracellular lipid droplets, nuclear migration and dissolution, and cell vacuolization in liver tissues. Six pathways were identified as the main enriched metabolic pathways according to the transcriptome profiling analysis, which were protein processing in endoplasmic reticulum, steroid biosynthesis, peroxisome, PPAR signaling pathway, glycolysis/gluconeogenesis and Insulin signaling pathway. The expressions of the important differentially expressed genes were verified by qPCR analysis, including erola, LOC100692144, sqle, cratb, pipox, cpt1a2b, hik and acss2l, ehhadh, prkcz, fasn and plaa, which showed the same expressions trends as those of RNA-Seq. Conclusions: The Nile tilapia strain improves the abilities of hypoxia response through energy metabolism. Antioxidant enzyme measurements in the liver indicate that these five antioxidant enzymes play important roles in protecting the body from hypoxic damage. The histological changes in liver cells indicate that the damage caused by hypoxia stress. The immune-related metabolic pathways and energy metabolism-related pathways were obtained by transcriptome profiling, and these metabolic pathways and the differentially expressed genes selected from these metabolic pathways may be involved in the mechanism of hypoxia tolerance in this strain. These findings provide a better understanding of the hypoxia response mechanism of fish, and represent a useful resource for the genetic breeding of O. niloticus. [ABSTRACT FROM AUTHOR]

There is a growing interest in Atlantic salmon (Salmo salar) aquaculture to extend the time fish are reared in freshwater (FW) recirculating aquaculture systems (RAS), producing larger FW salmon that can then be induced to undergo smoltification before transfer into marine net pens for grow‐out and harvest. Smolts can be produced by photoperiod (PT) manipulation in RASs, but little is known about how delaying smoltification to larger body sizes affects susceptibility to elevated CO2 levels (hypercapnia), which can occur at high stocking densities in FW RAS or during transport from FW RAS rearing facilities to marine net pens. To address this, Atlantic salmon were reared from hatch to one of three different sizes (~230, ~580, or ~1300 g) in FW (3 ppt) under continuous light (24:0, light:dark). Once fish reached the desired sizes, a group of salmon were maintained on continuous light 24L:0D to serve as a control salmon. A second group of salmon were exposed to 8 weeks of 12L:12D and then to 4 weeks of 24L:0D to serve as PT treatment salmon, which is the PT manipulation commonly used in Atlantic salmon aquaculture to induce smoltification. At the end of PT manipulation, both control and PT treatment salmon were exposed to 0% or 1.5% CO2 (30 mg/L) for 96 h in FW and then transferred to air‐equilibrated seawater (SW, 35 ppt, normocapnia). Salmon were sampled at the end of the 96‐h FW CO2 exposure and at 24 h and 7 days in SW for measurements of blood ion/acid–base status, muscle water content (MWC), and gill and kidney Na+/K+ ATPase (NKA) activity. Exposure to 96 h of CO2 in FW resulted in acid–base disturbances in fish from all three size classes, with decreases in blood pH and increases in blood PCO2 and plasma [HCO3−] but no mortality. Despite these large acid–base disturbances in FW, after transfer to normocapnic SW, there were no significant effects of CO2 exposure on extracellular blood pH, intracellular red blood cell pH, or plasma osmoregulatory status for all three sizes of post‐smolt salmon. In general, SW transfer was associated with significant increases in plasma ions and osmolality, as well as gill and kidney NKA activity after 24 h and 1 week in SW with no significant impacts between different sizes of salmon. Thus, exposure to 30 mg CO2/L that mimics levels experienced during transport from FW RAS to an SW transfer site may have minimal effects on Atlantic salmon smolts up to 1300 g. [ABSTRACT FROM AUTHOR]

This study aimed to conduct a multidisciplinary investigation integrating detailed morphology, molecular characterization, water parameters, histopathology alteration, and the trials of treatment of Clinostomum spp. In this study, 300 Nile tilapia (Oreochromis niloticus) were collected from the farmed and wild Nile River at Al Bahr Al Aazam, Giza Governorate to assess Clinostomid infection prevalence. Fish and water samples were collected from private fish farms, and water drains at Dakahlia, and Giza, Egypt. Analysis of the water revealed inadequate water quality, particularly in the fish farms. Snails and piscivorous birds were abundant at fish collection sites. The recovered Clinostomid MCs morphological characteristics and COI gene sequence analysis identified them as Clinostomum complanatum, C. phalacrocoracis, and Euclinostomum heterostomum. Clinostomid MCs disturbed the fish's hematological and biochemical blood parameters. Bath treatment of parasitized fish with praziquantel (2 mg/L for 24 h) revealed a significant reduction in the number of vital MCs vs. infected fish (non-treated). Praziquantel (PZQ) is an effective and safe therapy for controlling Clinostomid infections affecting farmed Nile tilapia. The current findings indicate a link between poor environmental conditions and Clinostomum infections in tilapia. The study highlights the impacts of Clinostomid MCs on fish health and recommends bath treatment with PZQ as an efficient control method for these dangerous parasites to protect human and fish health. [ABSTRACT FROM AUTHOR]

Background: Ochratoxin A (OTA) is a toxin widely found in aquafeed ingredients, and hypoxia is a common problem in fish farming. In practice, aquatic animals tend to be more sensitive to hypoxia while feeds are contaminated with OTA, but no studies exist in this area. This research investigated the multiple biotoxicities of OTA and hypoxia combined on the liver of grass carp and explored the mitigating effect of curcumin (CUR). Methods: A total of 720 healthy juvenile grass carp (11.06 ± 0.05 g) were selected and assigned randomly to 4 experimental groups: control group (without OTA and CUR), 1.2 mg/kg OTA group, 400 mg/kg CUR group, and 1.2 mg/kg OTA + 400 mg/kg CUR group with three replicates each for 60 d. Subsequently, 32 fish were selected, divided into normoxia (18 fish) and hypoxia (18 fish) groups, and subjected to hypoxia stress for 96 h. Results: CUR can attenuate histopathological damage caused by coming to OTA and hypoxia by reducing vacuolation and nuclear excursion. The alleviation of this damage was associated with the attenuation of apoptosis in the mitochondrial pathway by decreasing the expression of the pro-apoptotic proteins Caspase 3, 8, 9, Bax, and Apaf1 while increasing the expression of the anti-apoptotic protein Bcl-2, and attenuation of endoplasmic reticulum stress (ERS) by reducing Grp78 expression and chop levels. This may be attributed to the fact that the addition of CUR increased the levels of catalase (CAT) and glutathione reductase (GSH), increased antioxidant capacity, and ensured the proper functioning of respiratory chain complexes I and II, which in turn reduced the high production of reactive oxygen species (ROS), thus alleviating apoptosis and ERS. Conclusions: In conclusion, our data demonstrate the effectiveness of CUR in attenuating liver injury caused by the combination of OTA and hypoxia. This study confirms the feasibility and efficacy of adding natural products to mitigate toxic damage to aquatic animals. [ABSTRACT FROM AUTHOR]

Coordinated responses to threats are important for predator evasion in many species. This study examines the effect of developmental social experience on antipredator behavior and group cohesion in a highly gregarious catfish that communicates via tactile interaction, Corydoras aeneus. We reared fish either in a mixed‐age group of age‐matched peers and adult C. aeneus (mixed‐age condition, or MAC), or with age‐matched peers only (same‐age condition, or SAC). A startle test was conducted with small groups of subadults from either social rearing condition. Prior to any startle events, SAC subadults had increased tactile communication compared to MAC subadults, but SAC individuals were overall less active. SAC fish exhibited a stronger antipredator response to startles, and were more likely to freeze or take refuge in cover in response to a startle than MAC fish. MAC fish tended to respond to startle events by maintaining or decreasing their cohesion, whereas SAC fish tended to maintain or increase their cohesion. These behavioral differences are attributed to MAC fish developing with group protection as a result of shoaling with adults, resulting in reduced antipredator responses when reared with adults. This study underscores how social context during development can be critical in shaping how individuals perceive and respond to potential threats in their environment. [ABSTRACT FROM AUTHOR]

Biofloc technology (BFT) systems heavily rely on microbiota to mitigate ammonia toxicity and manage essential nutrient cycling. Understanding the diversity and functional role of microbiota within BFT-applied aquaculture systems is crucial for ensuring sustainable operations. Though some studies exist on BFT microbiota, research on microbial differences in Japanese eel aquaculture is still limited, hindering the wider application of BFT systems. In this study, we analyzed the characteristics of water quality factors and microbiota in Japanese eel (Anguilla japonica) breeding water, applying the BFT system. Using a metabarcoding approach, the diversity and community structure of aquatic microbiota were compared between BFT and continuous flow (CF) systems. The pH was significantly higher in CF water, while total ammonia nitrogen (TAN) and nitrite (NO2−-N) was higher in BFT water. Alpha diversity was significantly higher in BFT compared to CF systems, and it was correlated significantly with pH and TAN. In both BFT and CF water, the phyla Proteobacteria and Bacteroidota were found to be the most abundant. In the BFT water, a diverse array of bacterial taxa, including BFT-specific clades, were consistently present, while the microbiota in CF water was more variable and contained fewer specific taxa. In addition, bacterial functions related to nitrate reduction, sulfur compound oxidation, and chitinolysis were significantly more abundant in BFT than in CF systems. These findings highlight differences in water quality and microbiota between aquaculture systems, which can inform future research on the use of BFT for sustainable fish farming. [ABSTRACT FROM AUTHOR]

Simple Summary: This study investigated the response of goldfish (Carassius auratus) to different management conditions by assessing their oxygen consumption using an intermittent respirometry system, which serves as an indicator of metabolic rate. Goldfish consumed more oxygen during the day than at night, agreeing with the diurnal pattern of this teleost. Feeding to satiety increased their oxygen consumption by 35%, peaking 3 h after eating and returning to the normal routine values after 7 h. Handling the fish for five minutes caused a 140% increase in oxygen use, which returned to normal after 2.5 h. Increasing the water temperature gradually to 30 °C resulted in a 200% increase in oxygen consumption 2.5 h after the start of the temperature increase. Common aquaculture anesthetics also affected oxygen use for at least 4 h post-recovery. These findings suggest that metabolic rate is a valuable indicator of how goldfish respond to different practices that might increase their energy expenditure and stress. Therefore, intermittent respirometry, which measures oxygen consumption over time, is recommended to help understand and improve fish welfare in aquaculture. This study examined the metabolic rate (MO2, oxygen consumption) of goldfish (Carassius auratus) under normal management conditions in aquaculture. Using an intermittent respirometry system, we assessed daily variations and the effects of feeding, handling, temperature increase, and anesthetics. MO2 exhibited a daily rhythm, with higher values during day. Feeding to satiety produced a 35% increase in MO2 compared to fasted animals, with a maximum peak after 3 h and returning to baseline after 7 h. Handling stress (5 min) produced a 140% MO2 peak (from 180 to 252 mg O2 kg−1 h−1), returning to the routine MO2 after 2.5 h. An increase in water temperature (+0.1 °C min−1) up to 30 °C caused MO2 to peak at 200% after 2.5 h from the start of the temperature increase. The use of common anesthetics in aquaculture (MS-222, 2-phenoxyethanol and clove oil in deep anesthesia concentration) affects MO2 during the first few minutes after anesthetic recovery, but also during the following 4 h. It can be concluded that the metabolic rate is a good indicator of the goldfish's response to aquaculture practices involving energy expenditure and stress. Thus, intermittent respirometry is a valuable non-invasive tool for understanding and improving fish welfare in aquaculture. [ABSTRACT FROM AUTHOR]

Simple Summary: The aquaculture industry is a major contributor to the supply of animal proteins. Parasitic diseases like the white sport disease caused by Ichthyophthirius multifiliis (ich) is a significant threat to fish production and welfare. Previous studies explored the fish immune response against ich. However, the effects of farming procedures such as fish handling were not studied in the context of white spot disease. Our studies investigated the impact of handling procedures (air exposure, chasing, transfer) on the fish's ability to fight the parasite compared to non-handled fish. The results indicated that the stress caused by handling did not change the amount of parasite detected in the fish, in the tank's water, or the fish's mortality. Nonetheless, several parameters of the fish immune response were significantly altered due to the handling procedures. Overall, our results suggested that the handling procedures investigated did not impair the fish's ability to fight the parasite. Farmed fish are regularly subjected to various stressors due to farming practices, and their effect in the context of a disease outbreak is uncertain. This research evaluated the effects of unpredictable repeated stress in rainbow trout challenged with the ciliate Ichthyophthirius multifiliis, known to cause white spot disease in freshwater fish. Before and after the pathogen exposure, fish were handled with a random rotation of three procedures. At 7 days post-infection (dpi), the parasite burden was evaluated in fish and in the tank's water, and the local and systemic immune responses were investigated in the gill and spleen, respectively. The fish mortality was recorded until 12 dpi, when all the fish from the infected groups died. There was no statistical difference in parasite burden (fish and tank's water) and infection severity between the two infected fish groups. The immune gene expression analysis suggested a differential immune response between the gill and the spleen. In gills, a T helper cell type 2 immune response was initiated, whereas in spleen, a T helper cell type 1 immune response was observed. The stress has induced mainly upregulations of immune genes in the gill (cat-1, hep, il-10) and downregulations in the spleen (il-2, il-4/13a, il-8). Our results suggested that the unpredictable repeated stress protocol employed did not impair the fish immune system. [ABSTRACT FROM AUTHOR]

Flavobacterium is a genus of microorganisms living in a variety of hosts and habitats across the globe. Some species are found in fish organs, and only a few, such as Flavobacterium psychrophilum and Flavobacterium columnare, cause severe disease and losses in fish farms. The evolution of flavobacteria that are pathogenic to fish is unknown, and the protein changes accountable for the selection of their colonization to fish have yet to be determined. A phylogenetic tree was constructed with the complete genomic sequences of 208 species of the Flavobacterium genus using 861 softcore genes. This phylogenetic analysis revealed clade CII comprising nine species, including five pathogenic species, and containing the most species that colonize fish. Thirteen specific amino acid changes were found to be conserved across 11 proteins within the CII clade compared with other clades, and these proteins were enriched in functions related to replication, recombination, and repair. Several of these proteins are known to be involved in pathogenicity and fitness adaptation in other bacteria. Some of the observed amino acid changes can be explained by preferential selection for certain codons and tRNA frequency. These results could help explain how species belonging to the CII clade adapt to fish environments. [ABSTRACT FROM AUTHOR]