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Integrated multi trophic aquaculture (IMTA) is well developed in seawater, while the only suitable organisms for bioremediation in freshwater are bivalves. The aim of this research has been to investigate a novel system, based on freshwater bivalves integrated with rainbow trout, for the bioremediation of inland aquaculture systems. The Unionid species selected for the experiments was Sinanodonta woodiana. Five mesocosm experiments were conducted to evaluate the efficiency of mussels in filtering the total bacteria and Aeromonas hydrophila, as well as their clearance efficiency on trout farm wastewater. The temperatures, dissolved oxygen, nitrates, and phosphates were monitored and were all within the physiological tolerance range of the species in all the experiments. The feasibility of bioremediation with S. woodiana in trout farming has thus been demonstrated, and among the tested rearing densities (3.75; 7.5; 15; 30 and 60 kg m -3 ) that of 7.5 kg m -3 was found to be optimal. The net reduction of the total bacterial concentration was as much as 72%, while that of A. hydrophila reached a level of 95-98%. No relevant effects of the mussels on particulate suspended material or sedimented material was observed, regardless of the temperature. The efficiency of freshwater bivalves in reducing the bacterial load, in particular toward A. hydrophila, indicates a bioremediation system with the possibility of interesting applications on inland fish farms, and as a biotechnological tool against the diffusion of antibiotic resistance in aquaculture., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea) is the causative agent of proliferative kidney disease (PKD), which affects both wild and farmed salmonid fish. The objective of this study was to outline differences in susceptibility to PKD in different salmonid species, hybrids and breeding lineages. Susceptibility to T. bryosalmonae infection was established based on cumulative mortality, pathological findings and detection of T. bryosalmonae in the kidney using immunohistochemistry and molecular methods. Determination of pure and hybrid individuals of different species in the genus Salvelinus, and dissimilarity of rainbow trout lineages, was performed using traditional polymerase chain reaction (PCR) and microsatellite analyses. Rainbow trout displayed higher disease severity compared with brook trout and Alsatian charr. Moreover, the results indicated differences in infection susceptibility, not only among different salmonid species but also among different lineages of charr and rainbow trout. Our study indicated that some salmonid species and even different lineages of the same species are more suitable for farming under PKD pressure., (© 2020 John Wiley & Sons Ltd.)

Emamectin, a neurotoxic agent, is a semi-synthetic insecticide that belongs to the Avermectin family and is used against helmintic infections in the Salmonidae family. Its secondary effects are not clear; thus, the aim of this study was to investigate the only effects of emamectin benzoate on various biochemical parameters (AST, ALT, GGT, total protein, albumin and glucose) in serum and expressional changes of IL-1β, TNF-α, HSP70 and IL-8 in liver and spleen. For the purpose stated above, rainbow trout (n = 15) were administered 50 μg EB per kg fish daily for 7, 14 and 21 days. The results indicated that weight gains did not change (p  >  0.05), AST increased at day 21 (p < 0.05), while the changes of other biochemical parameters were not significant (p > 0.05). The changes in expression of IL-1β, TNF-α and HSP70 were significant (p < 0.05), while the changes of IL-8 expressions were not significant (p ˃ 0.05). In a conclusion, EB changed immun and stress-related gene expression in liver and spleen, and furthermore, AST changed in a dose- and time-dependent manner. The results imply that emamectin benzoate cause stress. This study is helpful to understand the effects of avermectin pharmaceutical family.

Copper is known to interfere with fish olfaction. Although the chemosensory detection and olfactory toxicity of copper ions (Cu 2+ ) has been heavily studied in fish, the olfactory-driven detection of copper nanoparticles (CuNPs)-a rapidly emerging contaminant to aquatic systems-remains largely unknown. This study aimed to investigate the olfactory response of rainbow trout to equitoxic concentrations of CuNPs or Cu 2+ using electro-olfactography (EOG, a neurophysiological technique) and olfactory-mediated behavioural assay. In the first experiment, the concentration of contaminants known to impair olfaction by 20% over 24 h (EOG-based 24-h IC20s of 220 and 3.5 μg/L for CuNPs and Cu 2+ , respectively) were tested as olfactory stimuli using both neurophysiological and behavioural assays. In the second experiment, to determine whether the presence of CuNPs or Cu 2+ can affect the ability of fish to perceive a social cue (taurocholic acid (TCA)), fish were acutely exposed to one form of Cu-contaminants (approximately 15 min). Following exposure, olfactory sensitivity was measured by EOG and olfactory-mediated behaviour within a choice maze was recorded in the presence of TCA. Results of neurophysiological and behavioural experiments demonstrate that rainbow trout can detect and avoid the IC20 of CuNPs. The IC20 of Cu 2+ was below the olfactory detection threshold of rainbow trout, as such, fish did not avoid Cu 2+ . The high sensitivity of behavioural endpoints revealed a lack of aversion response to TCA in CuNP-exposed fish, despite this change not being present utilizing EOG. The reduced response to TCA during the brief exposure to CuNPs may be a result of either olfactory fatigue or blockage of olfactory sensory neurons (OSNs) by CuNPs. The observed behavioural interference caused by CuNP exposure may indicate that CuNPs have the ability to interfere with other behaviours potentially affecting fitness and survival. Our findings also revealed the differential response of OSNs to CuNPs and Cu 2+ ., (Copyright © 2020. Published by Elsevier Ltd.)

This study aimed to evaluate the fate of Listeria monocytogenes in water microcosm and rainbow trout fillet under salinity stress of 0% and 30% NaCl at refrigerator temperature (4 ± 2 ℃). Bacterial culturability was studied by standard culture and colony count method. Reverse transcription-PCR (RT-PCR) of 16 S rRNA gene was used to detect viability of non-culturable bacteria. Also, the qualitative expression of pathogenic genes ( hly and inlA ) was studied using RT-PCR. The results showed that bacteria in water microcosm lost their culturability at 13 days under 0% salinity (starvation or distilled water) and at 27 days under 30% salinity; however, bacteria in rainbow trout fillet remained culturable under 0% and 30% NaCl. RT-PCR of 16 S rRNA gene was positive for all treatments during the period of this study, indicating the entering of L. monocytogenes into the viable but non-culturable state in water microcosm under 0% and 30% NaCl. Also, viable but non-culturable L. monocytogenes retained the expression of hly and inlA genes. So, it could be concluded that L. monocytogenes in viable but non-culturable state can cause serious health problems and further investigation is necessary to elucidate the effects of other processing and storage conditions (light, dark, smoking, etc.) on behavior of L. monocytogenes in smoked and salted fish.

In this study, we analyzed the gene structure, chemical characterizations, chromosome locations, evolutionary relationship, and expression profile of hsp90 genes with online database. In addition, the expression levels of hsp90s were also investigated under heat stress by quantitative real-time (qRT)-PCR. A total of eight hsp90 genes were identified from the rainbow trout genome. They were all distributed on chromosomes 2, 4, 8, and 13. The molecular weight ranged from 78.93 to 91.39 kDa, and the isoelectric point ranged from 4.84 to 4.96. The eight hsp90 genes were clustered into six subfamilies (A, B, C, D, E, and F). Genetic structure and conserved domain analysis revealed that all eight hsp90 genes had only one exon, and motif 1-motif 10 was shared by most genes. According to RNA-seq analysis of rainbow trout liver and head kidney, a total of seven out of eight genes were significantly upregulated under heat stress, and qRT-PCR was carried out on these seven genes; the expression levels of these genes were significantly upregulated under heat stress. The significantly regulated expressions of hsp90 genes under heat stress indicated that hsp90 genes are involved in heat stress response in rainbow trout. This study provides a theoretical basis for further study on the role of hsp90 in the heat stress tolerance of rainbow trout.

This work describes a primer pair and a high-throughput SYBR Green I-based real-time PCR protocol combined with melting curve analysis for identification and quantification of Vagococcus salmoninarum in bacterial cultures and infected fish tissues. The 16S rRNA gene was selected for the design of the primer pair (SalF and SalR). The sensitivity and specificity of this primer pair were compared with other previously designed for conventional PCR. Although both primer pairs showed 100% specificity using pure bacterial cultures or DNA extracted from bacteria or fish tissues, the primer pairs designed in this study showed the highest sensitivity with a detection limit of 0.034 × 10 0 amplicon copies per assay (equivalent to 2 × 10 -11  ng/µl, C q value of 30.49 ± 1.71). The developed qPCR protocol allowed the detection of V. salmoninarum in non-lethal and lethal fish samples with detection levels of 0.17 × 10 0 gene copies in tissues artificially infected and 0.02 × 10 0 in tissues of fish experimentally infected with V. salmoninarum. The high sensitivity of the developed method suggests that it could be considered as a useful tool for diagnosis of vagococcosis and the detection of V. salmoninarum in asymptomatic or carrier fish., (© 2019 John Wiley & Sons Ltd.)

The rainbow trout is a cold-water fish cultured in China. Heat stress has a serious impact on the summer survival and the yield of rainbow trout. A better understanding of the regulatory response of rainbow trout to heat stress will help in determining the relationship between heat stress signaling pathways and adaption mechanisms and help contribute to breeding new high-temperature tolerant strains of rainbow trout. In this study, the 48-h median lethal temperature (48h-LT 50 ) of rainbow trout was determined as 22.5°C. We developed control (16°C) and heat-treated (22.5°C) groups and extracted RNA from the head kidney tissues for high-throughput sequencing to study the microRNA (miRNA) expression profiles. Twelve up-regulated and five down-regulated miRNAs were identified between the control and heat-treated groups. A total of 22 target genes were predicted for 6 of the differentially expressed miRNAs, including 31 negative miRNA-mRNA interactions. Important regulatory pathways under heat stress are related to the metabolism and immune responses of the rainbow trout. Our findings provide preliminary data for investigating the high-temperature molecular mechanism of the rainbow trout and can help producers to reduce the economic losses caused by high temperature weather., (Copyright © 2019. Published by Elsevier Ltd.)

Here, we experimentally studied the site preference of Myxobolus cerebralis , one of the most pathogenic myxozoan (Cnidaria, Myxozoa) fish parasites, which causes whirling disease in salmonids. Parasite invasion was examined in three fish species with various susceptibility levels: the type host brown trout, the highly susceptible rainbow trout, and the non-susceptible gibel carp, in which parasite spores do not develop. We investigated the first two hours of fish invasion, and measured the site preference of triactinomyxons (TAMs) during attachment and penetration of fish in three body parts (gills, fins, skin). Infection prevalence and intensity were estimated using a species-specific nested PCR, optimised in the present study. The highest infection prevalence was detected in the most susceptible fish species, rainbow trout. Interestingly, higher prevalence was observed in gibel carp than in the type host, brown trout (95.2% vs. 85.7%). Considering body locations, remarkable differences were detected in infection intensities. The highest intensity was observed in fins, whereas skin was the least infected body part in every fish species examined. Infection prevalence and intensity did not differ significantly among fish species. Thus, we confirmed that M. cerebralis TAMs cannot discern fish species. Furthermore, we proved experimentally that fish fin is significantly more attractive to fish-invading parasite TAMs than gills or skin.

Environmental DNA (eDNA) analysis in the aquatic environment has emerged as a promising tool for diagnosis of the ecological status in comprehensive monitoring strategies and might become useful in context of the European Water Framework Directive (WFD) and other legislations to derive stressor-specific indicators. Despite many studies having made significant progress for the future use of eDNA in terms of ecosystem composition and detection of invasive/rare species in inland waters, much remains unknown about the transport and fate of eDNA under natural environmental conditions. We designed a specific dual-labelled probe to detect brown trout (Salmo trutta, L.) eDNA and used the probe to describe the fate of eDNA released from an aquaculture facility into the low mountain range stream Wehebach, Germany. The probe was shown to be specific to brown trout, as ponds housing rainbow trout (Oncorhynchus mykiss) did not test positive. Even though we observed different strengths of eDNA signals for three ponds containing different brown trout quantities, no significant correlation was found between biomass (kg/L) and eDNA quantity. Our results indicate that the release of DNA from brown trout might be life stage and/or age-dependent. The effluents of the aquaculture facility were a source of high levels of eDNA which resulted in the greatest abundance of brown trout eDNA directly downstream of the facility. Despite the natural occurrence of brown trout in the Wehebach, as shown by ecological investigations conducted by authorities of the federal state of North Rhine-Westphalia (Germany) and personal observations, we observed a significant decrease of relative abundance of eDNA in the Wehebach within the first 1.5 km downstream of the aquaculture. Our results suggest that concentrations of eDNA in running waters rapidly decrease under natural conditions due to dilution and degradation processes, which might have important implications for the utility of eDNA in environmental research., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The objectives of this study were to investigate the digestibility of pumpkin seed cake (PSC) for the rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), and effects on performance and product quality traits of four different fish species when PSC partially replaced fishmeal in extruded diets. A digestibility trial was carried out to determine apparent digestibility coefficients (ADC) for crude protein (CP), ether extract (EE) and gross energy (GE) of PSC fed to rainbow trout. In subsequent growth trials, effects on performance and morphological traits and fillet colour values of four different fish species [rainbow trout; brook trout, Salvelinus fontinalis (Mitchill, 1814); African sharptooth catfish, Clarias gariepinus (Burchell, 1822); and wels catfish, Silurus glanis (Linnaeus, 1758)] were evaluated when 60% of fishmeal protein of a reference diet was replaced by PSC protein (based on digestible CP). Nutrient ADC of PSC were high (CP: 89%, EE: 88% and GE: 84%). No significant effects on growth and only minor effects on fillet colour were detected in the trials. However, replacing fishmeal with PSC at the chosen level affected morphological traits and feed conversion in all four species to different extents. Replacement effects of PSC should be tested at lower levels of inclusion before conclusions are drawn on its suitability in fish diets.

Proliferative kidney disease (PKD) of salmonids caused by Tetracapsuloides bryosalmonae causes high mortalities of wild brown trout (Salmo trutta fario) and farmed rainbow trout (Oncorhynchus mykiss) at elevated water temperatures. Here the aim was to compare the temperature-dependent modulation of T. bryosalmonae in the two salmonid host species, which display different temperature optima. We used a novel experimental set-up in which we exposed brown trout and rainbow trout to an identical quantified low concentration of T. bryosalmonae for a short time period (1 hr). We followed the development of the parasite in the fish hosts for 70 days. PKD prevalence and parasite kinetics were assessed using qPCR. Exposures were performed at temperatures (12°C and 15°C) that reflect an environmental scenario that may occur in the natural habitat of salmonids. T. bryosalmonae infection was confirmed earliest in brown trout kept at 15°C (day 7 post-exposure) while, in all other groups, T. bryosalmonae was not confirmed until day 15 post-exposure. Moreover, significantly greater infection prevalence and a faster increase of parasite intensity were observed in brown trout kept at 15°C than in all other groups. These results indicate that PKD is differentially modulated by water temperature in related host species., (© 2017 John Wiley & Sons Ltd.)

The rainbow trout is an economically important fish in the world. The limited stress tolerance of this species to high summer-like temperatures usually leads to mass mortality and great economic loss. However, there is limited information on the mechanisms underlying moderate heat responses in the liver of the rainbow trout. Here, we performed transcriptome profiling of rainbow trout liver under moderate heat stress by using the Hiseq™ 4000 sequencing platform. More than 277 million clean reads were obtained from 6 libraries and aligned against the rainbow trout genome. A total of 128 unique transcripts were differentially expressed in the liver under heat-stress and control conditions, many heat shock protein genes for thermoregulation and some novel genes involved in heat stress were identified. Nine of the differently expressed genes were further validated by qRT-PCR. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed that several pathways, including those for protein metabolism, energy metabolism, and immune system, were influenced by heat stress. Moreover, an important protein-processing pathway in the endoplasmic reticulum (ER) was identified, and the key role of ER-associated degradation and function of calpain as an upstream regulator of apoptosis were confirmed under heat stress. The results of this study provide a comprehensive overview of heat stress-induced transcriptional patterns in rainbow trout liver and would be particularly useful for further studies on the molecular mechanisms underlying responses to heat stress in this species., (Copyright © 2017. Published by Elsevier B.V.)

Viral hemorrhagic septicemia virus (VHSV) is a rhabdovirus that causes one of the most important fish diseases in rainbow trout (Oncorhynchus mykiss) production industry. During the present study from October 2014 to July 2015, the virus causing viral hemorrhagic septicemia (VHS) was isolated and identified in rainbow trout farms from five of sixteen farms experiencing mass mortalities in six provinces of Iran with major trout production. Cumulative mortalities at VHSV-positive farms ranged from 30 to 70%. Clinical signs of disease included exophthalmia, petechial hemorrhages in the mandible and around the eyes, a swollen abdomen and darkening of the integument, widespread petechiae of the musculature and pyloric regions, severe congestion of the kidney, and pale enlarged livers. In addition, histopathologic examinations of tissues showed severe lesions in muscle, kidney and liver, which were compatible with those already described for VHS. Furthermore, homogenates tissues of diseased fish induced cytopathic effects (CPE) in CHSE-214 cells, and confirmatory diagnosis of VHS was made by RT-PCR reactions. To our knowledge, this is the first report of isolation and identification of VHSV from farmed trout in Iran, which may have originated from Europe., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: As a result of consumers' concerns about chemicals there is a particular interest in the food industry to use natural bio-preservatives such as antimicrobial enzymes for antimicrobial packaging. Based on the antimicrobial activity of the lactoperoxidase system (LPOS), the present study evaluated the coating effect of LPOS incorporated into chitosan solution (CH) on the quality and shelf life extension of rainbow trout during refrigerated storage (4 ± 1 °C), for a period of 16 days., Results: The results indicated that samples of the CH+LPOS group had significantly lower numbers of Shewanella putrefaciens, Pseudomonas fluorescens, and psychrotrophic and mesophilic bacteria than did the CH and control group during the entire storage period. Total volatile basic nitrogen (TVB-N) levels for the CH+LPOS samples (22.07 mg 100 g(-1)) did not exceed the limit of consumption (30-35 mg N 100 g(-1)), while the CH (31.03 mg 100 g(-1) ) and control groups (37.78 mg 100 g(-1) ) reached this level at days 12 and 16, respectively. Thiobarbituric acid values of the CH and CH+LPOS samples, ranged between 0.49 and 0.51 on day 0 and 4.59-4.66 mg kg(-1) on day 16, were significantly lower (P < 0.05) than the corresponding values of the control samples (0.47 on day 0 to 4.78 mg kg(-1) on day 16 of storage) during the chilled storage period., Conclusion: The coating treatments (CH and CH+LPOS) extended the shelf life of trout fillets by at least 4 days as compared to the control samples, so that they showed moderate to high acceptability in all investigated sensory attributes even on the 16th day of storage., (© 2014 Society of Chemical Industry.)

Purpose: The purpose of this paper is to assess the microbiological quality of rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis) from aquaculture farms located within the "Dolina Słupi" (Slupia Valley) Landscape Park, with a focus on regional sustainability practices. The research aims to evaluate water hygiene, the microbiological quality of feed, the prevalence of antibiotic-resistant bacteria, and their impact on the final quality of the farmed trout. This study seeks to contribute to the broader discourse on sustainable aquaculture by highlighting the importance of quality and risk management practices in maintaining food safety and environmental stewardship. Design/methodology/approach: The research employed a comprehensive microbiological analysis of samples collected from trout farms, including external and internal parts of trout, viscera, water, and feed. The study focused on identifying the presence of specific pathogens, such as Staphylococcus aureus, Escherichia coli, Salmonella spp., methicillin-resistant S. aureus, and vancomycin-resistant Enterococcus spp. The approach combined field sampling with laboratory testing to assess the hygienic conditions of the aquaculture environment and the quality of the final fish products. The research focuses on evaluating the microbiological quality of trout from aquaculture farms, with particular attention to local practices and their alignment with sustainability goals. Findings: The study revealed that the trout from the examined farms generally met good microbiological quality standards. Specifically, no methicillin-resistant S. aureus or vancomycin-resistant E. faecium and E. faecalis were detected, indicating effective risk management. However, Salmonella spp. were present in 30.5% of water samples, yet their presence did not significantly affect the contamination levels in fish samples. The highest S. aureus count was found on the skin of rainbow trout (1.5±101 cfu/g), while E. coli was detected on brook trout skin and viscera (11%). Enterococcus spp. were found in 17% of feed samples, but at low concentrations (<10 cfu/g). These results suggest that while overall microbiological quality is satisfactory, ongoing monitoring and adherence to good management practices are crucial for maintaining safety and quality in aquaculture. Research limitations/implications: One limitation of the research is the geographical focus on aquaculture farms within the "Dolina Słupi" Landscape Park, which may limit the generalizability of the findings to other regions or types of aquaculture systems. Future research could expand the scope to include a broader range of aquaculture environments and examine the long-term impact of sustainability practices on fish quality. Practical implications: The research underscores the critical role of continuous monitoring and rigorous quality management practices in aquaculture. The findings indicate that by implementing effective hygiene protocols and risk management strategies, aquaculture farms can achieve high safety standards for their fish products. These practices not only ensure product quality and consumer safety but also support the sustainability and economic viability of the aquaculture industry. Social implications: The study demonstrates that sustainable aquaculture enhances food security and environmental conservation. By promoting effective practices, it builds public trust in farmed fish, potentially influencing consumer behavior and supporting more sustainable industry practices. Originality/value: This paper contributes to the existing body of knowledge on sustainable aquaculture by providing empirical evidence on the microbiological quality of trout from farms in a specific regional context. It offers practical insights for industry professionals and consumers on optimizing quality and risk management to ensure safe and sustainable fish production. [ABSTRACT FROM AUTHOR]

The study investigated the effectiveness of three extruded feeds in the feed conversion index for the rainbow trout (Oncorhynchus mykiss Walbaum, 1792) reared at the Ain Aghbal fish farming station in Morocco. While the biochemical composition (moisture, protein, lipid, and carbohydrate percentages) and energy content (digestible and raw) of feeds A, B, and C are known, these factors alone are insufficient for selecting the optimal feed based on conversion index. The test was conducted over 222 days in tanks supplied with water from Oum Er-Rbia, flowing at 11.04m³/ h, with a water change every half an hour. Initial rearing conditions included a density of 1.58kg/ m³ and a volume-to-flow ratio of 1.05m³/ h. Fish were fed two to three times daily, depending on their growth stage. Results indicate that extruded feed B significantly improved the rainbow trout growth and achieved a conversion index not exceeding 0.9 for the trout weighing 1043g. [ABSTRACT FROM AUTHOR]

Kynurenic acid (KYNA) is a metabolite of tryptophan formed on the kynurenine pathway. Its pharmacological effects are relatively well characterized in mammals, whereas its role in fish is poorly understood. Therefore, the aim of the study was to expand the knowledge of KYNA's presence inside a fish's body and its impact on fish development and function. The study was performed on zebrafish larvae and adult rainbow trout. We provide evidence that KYNA is present in the embryo, larva and mature fish and that its distribution in organs varies considerably. A study of KYNA's effect on early larval development suggests that it can accelerate larval maturation, especially under conditions that are suboptimal for fish growth. Moreover, KYNA in concentrations over 1 mM caused morphological impairment and death of larvae. However, long-lasting exposure of larvae to subtoxic concentrations of KYNA does not affect the behavior of 5-day-old larvae kept under standard optimal conditions. We also show that ingestion of KYNA-supplemented feed can lead to KYNA accumulation, particularly in the pyloric caeca of mature trout. These results shed new light on the relevance of KYNA and provide new impulse for further research on the importance of the kynurenine pathway in fish. [ABSTRACT FROM AUTHOR]

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Aquafarms should reduce the use of fishmeal and fish oil in nutritional feed. One such accessible and relatively inexpensive food component that could successfully meet the challenge posed by aquaculture is algae. The objective of the present study was to evaluate the algae meal inclusion of Chlorella and Spirulina sp. in a diet for rainbow trout, evaluating its effects on fish growth, histological parameters and fillet quality. Experiments were carried out to replace 50% and 100% of fishmeal with Spirulina sp. and Chlorella vulgaris in feed for rainbow trout (Oncorhynchus mykiss W.) cultured in a recirculation system. At the end of the experimental period, the highest mean live weight was measured in rainbow trout fed a feed containing 50% algal meal in the feed. The absorptive vacuolization of cells was increased the most and lamina propria was average thickened when fed 50% algae diets. Fat droplets in the hepatocytes were larger in the 50% algae meal fed group, and their nuclei were replaced in the peripheral zone of the cells. Substitution of fishmeal with 50% algal meal in fish feed resulted in a 36.44% reduction in the lipid content of rainbow trout fillets compared to control fish. [ABSTRACT FROM AUTHOR]

Hybridization with introduced or invasive species is a major threat and driver of population declines in native salmonids. The rainbow trout (Oncorhynchus mykiss) is a major introduced and invasive species, often establishing entrenched naturalized populations. Here, we characterize population genetic variation of naturalized rainbow trout in a subset of Lake Tahoe tributaries to assess potential homing of rainbow trout to specific streams for spawning, thereby informing native Lahontan cutthroat trout (Oncorhynchus clarkii henshawi) reintroduction. Diploid, reproductively viable rainbow trout of commonly raised hatchery strains were stocked into Lake Tahoe from the late 1800s until the early 2000s by California and Nevada fish and wildlife agencies. Since 2007, however, triploid individuals comprise the bulk of rainbow trout planted. Despite dispersal from stocking locations across regions, our analyses revealed variation in population differentiation among tributaries, with individuals from spatially proximate streams clustering across multiple population genetic analyses. Although subtle, we detected evidence for genetic differentiation among tributaries from the southern, western, and northern regions, including surprising structure involving a single tributary. These results illustrate the extent of differentiation within and among streams and could inform possibilities for and implications of rainbow trout removal and Lahontan cutthroat trout reintroduction into its historical habitat. [ABSTRACT FROM AUTHOR]

[Display omitted] N -(1,3-dimethylbutyl)- N ′-phenyl- p -phenylenediamine quinone (6PPDQ) has attracted significant attention due to its highly acute lethality to sensitive salmonids. However, studies investigating the mechanisms underlying its acute toxicity have been lacking. In this work, we demonstrated the sensitivity of rainbow trout to 6PPDQ-induced mortality. Moribund trout exhibited significantly higher brain concentrations of 6PPDQ compared to surviving trout. In an in vitro model using human brain microvascular endothelial cells, 6PPDQ can penetrate the blood–brain barrier and enhance blood–brain barrier permeability without compromising cell viability. The time spent in the top of the tank increased with rising 6PPDQ concentrations, as indicated by locomotion behavior tests. Furthermore, 6PPDQ influenced neurotransmitter levels and mRNA expression of neurotransmission-related genes in the brain and exhibited strong binding affinity to target neurotransmission-related proteins using computational simulations. The integrated biomarker response value associated with neurotoxicity showed a positive linear correlation with trout mortality. These findings significantly contribute to filling the knowledge gap between neurological impairments and apical outcomes, including behavioral effects and mortality, induced by 6PPDQ. [ABSTRACT FROM AUTHOR]

This study aimed to obtain optimized mixture with three essential oils (EOs) for maximum antioxidant activity through the augmented simplex-centroid mixture design and evaluate the effect of this optimized blend on total aerobic psychrotrophic count (TAPC), lipid and protein oxidation, instrumental color parameters and texture profile in rainbow trout fillets at refrigerated storage for nine days. Considering the DPPH and FRAP assays, the ideal EO blend was 66% lemongrass and 34% oregano. During refrigerated storage, this blend at 2000 ppm was equally effective as BHT (100 ppm) (p > 0.05), mitigating the discoloration (a* and b*), lipid, and protein oxidation in 38.83%, 12.95%, 76.13%, and 35.13%, respectively, besides shows greater effectiveness for preserving texture changes (p < 0.05) and extending the shelf life in 13 h. The lemongrass + oregano EO blend reveals a promising natural alternative to enhance the quality of rainbow trout fillets under refrigerated storage. Furthermore, the multiresponse optimization showed to be a strong ally in enabling the use of these EOs by food industries. [ABSTRACT FROM AUTHOR]

Introduction: Fish rest raw material generated from the fish processing industry may be a useful resource for recovery of added value compounds. The application of non-thermal novel technologies can improve the extraction. High-pressure processing (HPP) has long been used for the preservation and extension of the shelf life of seafood. It also constitutes a promising technology for the increased recovery of valuable compounds, such as lipids and proteins. The objective of this study was to assess the yield and the chemical composition of the fractions obtained after enzymatic hydrolysis on a mixture of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) rest raw material pretreated by high-pressure (HP). Methods: Six different pretreatments were applied prior to enzymatic hydrolysis; 600 MPa x 8 min, 600 MPa x 4 min, 400 MPa x 8 min, 400 MPa x 4 min, 200 MPa x 8 min, 200 MPa x 4 min. Results and discusssion: These applied pretreatments did not yield higher oil extraction compared to the control. However, the fish protein hydrolysates (FPH) contained higher amount of protein when compared to the FPH obtained from the control. [ABSTRACT FROM AUTHOR]

Climate change is increasing the frequency, severity, and extent of wildfires and drought in many parts of the world, with numerous repercussions for the physical, chemical, and biological characteristics of streams. However, information on how these perturbations affect top predators and their impacts on lower trophic levels in streams is limited.The top aquatic predator in southern California streams is native Oncorhynchus mykiss, the endangered southern California steelhead trout (trout). To examine relationships among the distribution of trout, environmental factors, and stream invertebrate resources and assemblages, we sampled pools in 25 stream reaches that differed in the presence (nine reaches) or absence (16 reaches) of trout over 12 years, including eight reaches where trout were extirpated during the study period by drought or post‐fire flood disturbances.Trout were present in deep pools with high water and habitat quality. Invertebrate communities in trout pools were dominated by a variety of medium‐sized collector–gatherer and shredder invertebrate taxa with non‐seasonal life cycles, whereas tadpoles and large, predatory invertebrates (Odonata, Coleoptera, Hemiptera [OCH]), often with atmospheric breather traits, were more abundant in troutless than trout pools.Structural equation modelling of the algal‐based food web indicated a trophic cascade from trout to predatory invertebrates to collector–gatherer taxa and weaker direct negative trout effects on grazers; however, both grazers and collector–gatherers also were positively related to macroalgal biomass. Structural equation modelling also suggested that bottom‐up interactions and abiotic factors drove the detritus‐based food web, with shredder abundance being positively related to leaf litter (coarse particulate organic matter) levels, which, in turn, were positively related to canopy cover and negatively related to flow. These results emphasise the context dependency of trout effects on prey communities and of the relative importance of top‐down versus bottom‐up interactions on food webs, contingent on environmental conditions (flow, light, nutrients, disturbances) and the abundances and traits of component taxa.Invertebrate assemblage structure changed from a trout to a troutless configuration within a year or two after trout were lost owing to post‐fire scouring flows or drought. Increases in OCH abundance after trout were lost were much more variable after drought than after fire. The reappearance of trout in one stream resulted in quick, severe reductions in OCH abundance.These results indicate that climate‐change induced disturbances can result in the extirpation of a top predator, with cascading repercussions for stream communities and food webs. This study also emphasises the importance of preserving or restoring refuge habitats, such as deep, shaded, perennial, cool stream pools with high habitat and water quality, to prevent the extirpation of sensitive species and preserve native biodiversity during a time of climate change. [ABSTRACT FROM AUTHOR]

In this study, the impact of adding 10% or 20% torula yeast (PB TY10 and PB TY20) to a fishmeal‐free diet on digestibility and growth of juvenile rainbow trout was assessed. The yeast diets were compared with a plant‐only diet (PB) and a diet containing 20% fishmeal (FM). The apparent digestibility of dry matter, protein, energy, and ash of yeast in trout (~120 g) were 78.6%, 93.8%, 84.8%, and 48.7%, respectively. All PB diets had higher protein digestibility and PB TY20 had higher ash digestibility than the FM diet. To assess growth, trout (~44 g) were divided into triplicate tanks (30 per tank) and fed one of the four experimental diets for 12 weeks. The PB diet resulted in lower growth and daily feed intake (p < 0.05), but adding yeast significantly improved them. Final weight of PB TY10 did not differ significantly from that of FM. Expression of oclna and cldn15 in the proximal intestine increased in trout fed yeast (p < 0.05). Expression of tlr2, mcsfr, and tnfa, as well as the plasma lysozyme concentration, increased with PB TY20 (p < 0.05). In conclusion, torula yeast has the potential to improve the robustness and growth of rainbow trout in the context of fishmeal‐free diets. [ABSTRACT FROM AUTHOR]

An important concern of man has become to have high-quality food for a healthy life. Fish such as rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis) are an important bioindicator of pollution. The accumulation of heavy metals represents a potential danger to public health. Trout is preferred and consumed by many people so any possible risk of ingesting metals through food chains should be assessed. The main organs studied according to specialized literature regarding the accumulation of heavy metals are the liver an the kidney, these organs play an important role in preventing the transfer of heavy metals to other organs, for example muscle tissue. As is known, the pollution of aquatic ecosystems has a direct impact on the entire aquaculture activity. Therefore, the purpose of this study was to monitor metals present in the two trout species in different areas. [ABSTRACT FROM AUTHOR]

In this study, we investigated the dietary effects of dandelion root extract (DRE) on growth performance, body composition, serum biochemical parameters, intestinal and liver histology, and fish resistance against Lactococcus garvieae infection in the rainbow trout. In total, 540 rainbow trout fry (22.05±1.740 g and 13.03±0.470 cm) were used. Six experimental groups (control, 2.5 mL/kg (DRE-1), 5 mL/kg (DRE-2), 10 mL/kg (DRE-3), 20 mL/kg (DRE-4), and 40 mL/kg (DRE-5) dandelion root extract) with three replicates were formed. In each tank, 30 fish were placed and fed for 90 days, and the volume of water was adjusted to 80 L with a flow-through system. The results showed that the final fish weight, weight gain, specific growth rate, protein efficiency ratio, and protein deposition rate were significantly higher in the DRE-4 group, while the feed conversion ratio and fat deposition ratio were significantly lower compared to that in the control group (P<0.05). The viscerosomatic index and the hepatosomatic index decreased in the experimental groups depending on the concentration of the extract used, while the condition factor was higher than that in the control (P<0.05). The DRE significantly decreased glucose, cholesterol, triglyceride, low-density lipoprotein, alanine aminotransferase, and aspartate aminotransferase levels in blood serum in the fish from the experimental groups, but it significantly increased high-density lipoprotein, alkaline phosphatase, and total protein levels (P<0.05). Similarly, the DRE positively affected intestinal histology by increasing the stratum compactum, submucosa, lamina propria, villi length, villi width, absorption area, tunica muscularis thickness, mucosal folds, and goblet cell count. In the liver, depending on the high-fat diet (crude lipid = 20%), vacuolization areas, hepatocellular degeneration areas, apoptotic hepatocyte nucleus, and necrotic areas recorded in the control group decreased or even disappeared completely in the extract groups. The results of the challenge test showed that adding 2.5 mL/kg of the DRE to the feed positively affected the disease resistance against Lactococcus garvieae infection. The results of the quadratic polynomial regression showed that an average level of 23.91±1.048 mL/kg of DRE would be suitable for optimum fish growth. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Investigación e Innovación Agropecuaria y de Recursos Naturales is the property of Revista de Investigacion e Innovacion Agropecuaria y de Recursos Naturales RIIARn and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Anatolian Environmental & Animal Science is the property of Bulent Verep and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present study combined uniparental mtDNA and biparental SNPs to illuminate the invasion and colonization pathways of rainbow trout, Oncorhynchus mykiss, one of the world's most widespread invasive fishes, that has been intensively propagated in Chile, South America. The specific aims of the study were (i) to evaluate potential donor populations, which could be either from the species' native range in North America or from introduced populations in Europe, by comparing mtDNA D‐loop/control region haplotypes; and (ii) to assess the factors that have shaped genetic diversity and contemporary genetic structure of rainbow trout populations introduced to Chile through SNP genotyping. The authors comprehensively sampled 24 sites in 12 basins ranging from the High Andean Plateau (Altiplano, 18° S) to northern Patagonia (41° S). Results of the mtDNA data of naturalized trout populations from rivers in the Altiplano (northern Chile) differed from those collected in central and southern Chile, suggesting an origin from North American hatcheries. Naturalized trout populations in central and southern Chile, on the contrary, shared haplotypes with specimens found in European hatcheries. The southern and central Chile populations also contained rare haplotypes, possibly indicating potential spread through aquaculture escapes. Results of the SNP analysis revealed higher allelic richness for trout sampled in sites influenced by commercial aquaculture than sites without commercial aquaculture, likely due to increased admixture between aquaculture broodstock and naturalized trout. The analysis further uncovered some complex patterns of divergent trout populations with low genetic diversity as well as increased relatedness between individuals from isolated sites, suggesting possible local populations. A comprehensive characterization of genetic diversity and structure of rainbow trout should help identify management areas that may augment socioeconomic benefits while preventing the spread and further impacts on biodiversity. [ABSTRACT FROM AUTHOR]

Despite growing interest in conservation and re‐establishment of ecological connectivity, few studies have explored its context‐specific social–ecological outcomes. We aimed to explore social and ecological outcomes to changing stream connectivity for both stakeholders and native fish species impacted by habitat fragmentation and nonnative species. We (1) investigated stakeholder perceptions of the drivers and outcomes of stream connectivity, and (2) evaluated the effects of stakeholder‐identified connectivity and nonnative species scenarios on Yellowstone cutthroat trout (YCT) populations. Our study was conducted in the Teton River, Idaho, USA. We integrated two modeling approaches, mental modeling and individual‐based ecological modeling, to explore social–ecological outcomes for stakeholders and YCT populations. Aggregation of mental models revealed an emergent pattern of increasing complexity as more types of stakeholders were considered, as well as gaps and linkages among different stakeholder knowledge areas. These results highlight the importance of knowledge sharing among stakeholders when making decisions about connectivity. Additionally, the results from the individual‐based models suggested that the potential for a large, migratory life history form of YCT, in addition to self‐preference mating where they overlap with rainbow trout, had the strongest effects on outcomes for YCT. Exploring social and ecological drivers and outcomes to changing connectivity is useful for anticipating and adapting to unintended outcomes, as well as making decisions for desirable outcomes. The results from this study can contribute to the management dialogue surrounding stream connectivity in the Teton River, as well as to our understanding of connectivity conservation and its outcomes more broadly. [ABSTRACT FROM AUTHOR]

Objective: We explore apparent infection of Salmincola californiensis arising during investigations involving this lernaeopodid copepod parasitic on Pacific salmon and trout Oncorhynchus spp. Methods: We noted occasional unusual coloration of adult female copepods collected from the wild. These females were bright blue and pink in contrast to the cream white coloration characteristic of the copepod. We also observed that similar color patterns developed under laboratory settings when copepod eggs were held for hatching. In paired egg cases, we found consistent hatching failure of blue and pink eggs and patterns in apparent disease development that would be consistent with both vertical and horizontal transmission. Result: Attempts to identify the cause of the apparent infection using genetic methods and transmission electron microscopy were inconclusive. Conclusion: Iridovirus infection was initially suspected, but bacterial infection is also plausible. This apparent reduced hatching success of S. californiensis warrants further exploration as it could reduce local abundances. Given the potential importance of a disease impacting this copepod, a parasite that itself affects endangered and commercially important Pacific salmon and trout, future research would benefit from clarification of the apparent infection through additional sequencing, primer development, visualization, and exploration into specificity and transmission. Impact statementAn apparent infection of S. californiensis may impair hatching of this freshwater copepod parasite impacting Pacific salmon and trout. [ABSTRACT FROM AUTHOR]

Fish hatcheries across North America release billions of fish into the wild every year to augment harvest opportunities in sport, commercial, and tribal fisheries, as well as to recover depressed populations. Despite these benefits, wild fish populations may be negatively affected when hatchery fish compete and/or hybridize with native species. Native Westslope Cutthroat Trout Oncorhynchus clarkii lewisi have decreased by 90% across their historic range; however, the Flathead River in Montana is a rangewide stronghold for these imperiled fish. The primary threat to Westslope Cutthroat Trout is hybridization with invasive Rainbow Trout O. mykiss, which leads to hybrid swarm formation and genomic extinction. We collected Rainbow Trout in Mill Creek, a tributary of the Flathead River, downstream from a hatchery that produces the species, and used otolith 87Sr/86Sr to determine whether individual fish were inadvertently introduced from the hatchery. Differences in 87Sr/86Sr among water samples from Mill Creek and the marine‐derived hatchery food provided high‐classification accuracy to determine the natal origins of Mill Creek Rainbow Trout. We found that 83 of the 106 Rainbow Trout collected (78%) were of hatchery origin. Otolith microstructure analysis indicated these fish had been in Mill Creek for ~1–32 weeks prior to capture. Our results illustrate the utility of otolith 87Sr/86Sr to identify hatchery fish in natural habitats and point to a source of invasive Rainbow Trout that pose conservation risks to native fishes in the drainage. [ABSTRACT FROM AUTHOR]

Reservoirs are sometimes managed to meet agricultural and other water demands, while also maintaining streamflow for aquatic species and ecosystems. In the Henrys Fork Snake River, Idaho (USA), irrigation‐season management of a headwater reservoir is informed by a flow target in a management reach ~95 km downstream. The target is in place to meet irrigation demand and maintain aquatic habitat within the 11.4 km management reach and has undergone four flow target assignments from 1978 to 2021. Recent changes to irrigation‐season management to maximize reservoir carryover warranted investigation into the flow target assignment. Thus, we created a streamflow‐habitat model using hydraulic measurements, habitat unit mapping, and published habitat suitability criteria for Brown Trout (Salmo trutta), Rainbow Trout (Oncorhynchus mykiss), and Mountain Whitefish (Prosopium williamsoni). We used model output to compare habitat availability across two management regimes (1978–2017 and 2018–2021). We found that efforts to minimize reservoir releases in 2018–2021 did not reduce mean irrigation‐season fish habitat relative to natural flow, but did reduce overall fish habitat variability during the irrigation season compared to streamflow management in 1978–2017. Field observations for this research led to an adjusted flow target in 2020 that moved the target location downstream of intervening irrigation diversions. Using our model output, we demonstrated that moving the location of the target to account for local irrigation diversions will contribute to more consistently suitable fish habitat in the reach. Our study demonstrates the importance of site selection for establishing environmental flow targets. [ABSTRACT FROM AUTHOR]

This study explored changes in brain serotonin content and activity together with hypothalamic neuropeptide mRNA abundance around feeding time in rainbow trout, as well as the effect of one-day fasting. Groups of trout fed at two (ZT2) and six (ZT6) hours after lights on were sampled from 90 minutes before to 240 minutes after feeding, while additional groups of non-fed trout were also included in the study. Changes in brain amine and metabolite contents were measured in hindbrain, diencephalon and telencephalon, while in the diencephalon the mRNA abundance of tryptophan hydroxylase (tph1, tph2), serotonin receptors (5htr1a, 5htr1b and 5htr2c) and several neuropeptides (npy, agrp1, cartpt, pomca1, crfb) involved in the control of food intake were also assessed. The results showed changes in the hypothalamic neuropeptides that were consistent with the expected role for each in the regulation of food intake in rainbow trout. Serotonergic activity increased rapidly at the time of food intake in the diencephalon and hindbrain and remained high for much of the postprandial period. This increase in serotonin abundance was concomitant with elevated levels of pomca1 mRNA in the diencephalon, suggesting that serotonin might act on brain neuropeptides to promote a satiety profile. Furthermore, serotonin synthesis and neuronal activity appear to increase already before the time of feeding, suggesting additional functions for this amine before and during food intake. Exploration of serotonin receptors in the diencephalon revealed only small changes for gene expression of 5htr1b and 5htr2c receptors during the postprandial phase. Therefore, the results suggest that serotonin may play a relevant role in the regulation of feeding behavior in rainbow trout during periprandial time, but a better understanding of its interaction with brain centers involved in receiving and processing food-related signals is still needed. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the compliance with Good Aquaculture Practices (GAPs) in the Health Compliance Units (UPAs) during the incubation of rainbow trout eggs and to identify the presence of Aeromonas salmonicida and Aeromonas hydrophila using the Polymerase Chain Reaction (PCR) technique. Design/Methodology/Approach: Seven and three egg incubation UPAs were identified in Puebla and Veracruz, respectively. An structured questionnaire was applied to evaluate the compliance with the GAPs. Samples were collected from the trout avelin batches and were analyzed in search of A. salmonicida and A. hydrophila using the PCR technique. The results were compared with the health characteristics of the fish of each batch. Results: The GAP-certified UPAs comply with the recommendations made by the authorities and do not show morbidity. UPAs that comply with less GAP points have health issues. A. hydrophila was detected in batches with a lower compliance with the GAPs. The presence of A. salmonicida was not identified. Study Limitations/Implications: The lack of compliance with the GAPs can lead to infection by other trout pathogens (not taken into consideration in this study). Findings/Conclusions: Compliance with the GAPs reduces the health risk at the rainbow trout egg incubation UPAs. [ABSTRACT FROM AUTHOR]

Climate warming is increasing maximum temperatures during summer such that they more frequently exceed the thermal tolerances of ectotherms, particularly cold‐water fishes. One way that species can avoid thermal stress is by moving to thermal refuge habitats. Thermal refuges remain suitably cool during summer and are often complementary to foraging, spawning, and rearing habitats. Although the benefits associated with the thermal aspects of refuges are well studied, much less is known about potential costs associated with nonthermal aspects. For example, crowding of cold‐water fishes into seasonal refuge habitats could increase parasite loads and cause declines in fitness. We assessed lamprey and anchor worm parasitism in Upper Klamath Lake where adfluvial redband trout (Oncorhynchus mykiss newberrii) move to thermal refuge habitats during summer. We sampled trout in Upper Klamath Lake during spring and in adjacent thermal refuge habitats during summer. We also evaluated survival as a function of lamprey wounding using motion‐sensing radio tags. There was a fourfold decline in the number of lamprey wounds on trout upon the onset of thermal refuge use. In contrast, cases of severe anchor worm (≥20 sores) increased threefold during thermal refuge use. Survival in thermal refuge was not different for lamprey‐wounded trout than for trout that migrated to thermal refuge without lamprey wounds. We found that both parasites were absent in a lotic population of redband trout downstream that lacked access to thermal refuge. Thus, the effects of seasonal refuge use on parasite load varied depending on the parasite taxon considered and local habitat conditions, implying that managers will likely require empirical data for focal habitats and taxa to understand how parasitism affects thermal refuge use. [ABSTRACT FROM AUTHOR]

Smoking represents one of the oldest thermic processing methods of fish, and it was originally used to preserve fish for later meals, delaying spoiling. The objective of this study was to analyze the physicochemical and microbiological safety and quality of two traditionally smoked trout species (Oncorhynchus mykiss and Salvelinus fontinalis). We analyzed the effect of trout processed by traditional smoking, characterizing the samples according to the relationships existing between classical microbial analysis, physicochemical parameters, and the content of polycyclic aromatic hydrocarbons (PAHs). The microbial activity of the smoked fish was very low. Although traditional smoking implies high temperatures and direct exposure to the smoke, Benzo[a]pyrene, Benzo[b]fluoranthene, Benzo[k]fluoranthene, Dibenzo[a,h]anthracene, Benzo[g,h,i]perylene, and Indeno [1,2,3-cd]pyrene compounds had undetectable levels in the samples. The products obtained in this study did not exceed the maximum values imposed by EU legislation regarding the TVB-N values during the 30 days of the experiment. We conclude that traditionally smoked trout has many advantages in terms of quality and safety of the products. Thus, the obtained products are safe for consumption for at least 30 days after processing. [ABSTRACT FROM AUTHOR]

The melanocortin-4 receptor (MC4R) is essential for the modulation of energy balance and reproduction in both fish and mammals. Rainbow trout (Oncorhynchus mykiss) has been extensively studied in various fields and provides a unique opportunity to investigate divergent physiological roles of paralogues. Herein we identified four trout mc4r (mc4ra1, mc4ra2, mc4rb1, and mc4rb2) genes. Four trout Mc4rs (omMc4rs) were homologous to those of teleost and mammalian MC4Rs. Multiple sequence alignments, a phylogenetic tree, chromosomal synteny analyses, and pharmacological studies showed that trout mc4r genes may have undergone different evolutionary processes. All four trout Mc4rs bound to two peptide agonists and elevated intracellular cAMP levels dose-dependently. High basal cAMP levels were observed at two omMc4rs, which were decreased by Agouti-related peptide. Only omMc4rb2 was constitutively active in the ERK1/2 signaling pathway. Ipsen 5i, ML00253764, and MCL0020 were biased allosteric modulators of omMc4rb1 with selective activation upon ERK1/2 signaling. ML00253764 behaved as an allosteric agonist in Gs-cAMP signaling of omMc4rb2. This study will lay the foundation for future physiological studies of various mc4r paralogs and reveal the evolution of MC4R in vertebrates. [ABSTRACT FROM AUTHOR]

The effect of ellagotannins on the activity of peptidases of the intestinal mucosa and chyme of trout was studied. Experimental groups of fish were fed with an additive based on ellagotannins (with an active substance content of 0.38, 0.76, and 1.14 g/kg of food). Sampling was carried out in eight individuals from each group before the experiment and on days 15, 30, 45, and 60. The study showed that ellagotannins have a stimulatory effect on the activity of peptidases. The maximum increase in the enzymatic activity in the experimental groups compared with the control group was recorded on day 45 of the experiment. A more significant increase in the activity of peptidases of the intestinal mucosa compared with chyme was established. It is concluded that ellagotannins stimulate the initial stage of cleavage of protein components of food. [ABSTRACT FROM AUTHOR]

Objective: Although piscicides are an important tool for native fish management, our understanding of native fish population dynamics posttreatment (i.e., in putatively vacant habitat) is limited. Methods: Here, we describe long‐term trends in size and abundance of Cutthroat Trout Oncorhynchus clarkii in Lower Boulder Lake and Boulder Creek (Montana). Result: No significant differences were found before and after treatment with rotenone in mean length and population density in Boulder Creek. Posttreatment genetic samples from Boulder Lake and upper Boulder Creek consisted entirely of the Westslope Cutthroat Trout Oncorhynchus clarkii lewisi used to refound the population. Middle and lower Boulder Creek genetic samples contained 99.4% and 98.4% Westslope Cutthroat Trout, indicating that some nonnative (Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri hybrid) fish survived the treatment. Population demographics showed robust recovery posttreatment; however, genetic results revealed the limitations of a one‐time treatment—that is, an incomplete fish kill. Conclusion: We demonstrate that Cutthroat Trout populations achieve recovery after rotenone treatment in the long term, but one‐time rotenone treatments on large drainages often fail to totally eradicate populations. Therefore, managers should plan on multiple treatments and utilize environmental DNA to help achieve total removal of target species. Impact statementThe Westslope Cutthroat Trout is an iconic native species of the northern Rocky Mountains, but hybridization with introduced species, including Rainbow Trout and Yellowstone Cutthroat Trout, has greatly reduced the distribution and abundance of genetically pure populations. This case study reviews an attempt to remove a hybridized population using a single rotenone treatment before restocking with a hatchery‐reared, genetically pure population. These results can aid fisheries managers as they plan and implement fish removal projects. [ABSTRACT FROM AUTHOR]

Arsenic is one of the most abundant elements on earth. Arsenic, also called metalloid, is used as a raw material in many industries. Arsenic causes the acceleration of free radical production in the body and the resulting oxidative stress. In juvenile trout, the interactions of arsenic with metacomposition, biochemical analysis, and apoptosis stimuli were investigated. Results were demonstrated by several marker applications, including oxidative stress parameters, proinflammatory cytokine expressions, DNA damage, and apoptosis markers. In our study, arsenic was applied to juvenile trout (Oncorhynchus mykiss) at concentrations of 25, 50, and 75 mg/L for 96 h. After exposure, the brain tissues of the fish were collected and homogenized. SOD the GSH-Px, CAT, and MDA levels were determined by spectrophotometric methods in the supernatants from the brain tissues of the juvenile trout. Levels of NF-kB, TNF-α, IL-6, Nrf-2, GSH, caspase-3, AChE, and 8-OHdG were determined with an ELISA kit. When the brain tissues of the fish were examined after the study, it was found that the levels of NF-kB, TNF-α, IL-6, Nrf-2, Caspza-3, MDA, and 8-OHdG increased, and the levels of GSH, CAT, SOD, AChE, and GSH-Px decreased. It was found that oxidative stress occurred as a result of the effect of the heavy metal arsenic in the brain tissues of the fish after application. [ABSTRACT FROM AUTHOR]

The muscle hardness of fish is an important parameter associated with meat quality, and the post-mortem decrease in the pH of fish tissue pH affects its physical properties. We hypothesized that maintaining a high pH in fish tissue after death would prevent protein denaturation and consequent textural deterioration. This study aimed to determine the effectiveness of sodium bicarbonate (SBC) injections in preventing tissue softening caused by low pH after death in trout. We injected varying molar concentrations of SBC in rainbow trout (Oncorhynchus mykiss; 0 M, 0.5 M, 0.75 M, and 1 M) after harvest, and the product quality was assessed at 0, 24, 48, 72, and 96 h of ice storage. Quality was evaluated using proximate analyses for color, pH, water holding capacity (WHC), texture profile, and rigor index. The 0 M group had the lowest pH, and the 0.75 M group had the highest pH at all time points during storage. We observed improved tissue texture during storage in fish treated with 0.75 and 1 M SBC. The texture profile analysis showed higher hardness, frangibility, and stickiness in the tail than in the other regions. These varying results can be explained by significant differences between parts of the fish and sampling point selection. We also observed the highest pH and WHC values in the groups injected with 0.75 and 1 M SBC during storage. [ABSTRACT FROM AUTHOR]

BACKGROUND: Infectious diseases and microbial antibiotic resistance are the major problems of fish farming industry annually causing remarkable losses. Apart from the economic losses caused by these infections, some of these agents are zoonotic and may be transmitted to humans. OBJECTIVES: This study was aimed to identify the common causative agents of infections in rainbow trout farms and to determine their antibiotic resistance toward some common antibiotics. METHODS: Sampling was performed during a nine-month period between March and December 2021 by visiting and inspecting rainbow trout farms and the affected fish with disease symptoms were obtained from the farmed fish in Mazandaran, Lorestan, Chaharmahal and Bakhtiari and Zanian provinces. Bacterial culture was undertaken from anterior kidney or spleen organs and the isolated bacterial strains were identified by phenotyping, biochemical and molecular assays. Antibiotic resistance pattern was evaluated by disk diffusion method (DDM) and minimum inhibition concentration against erythromycin, oxytetracycline, florfenicol, enrofloxacin and nitrofurantoin. RESULTS: Seventy-four bacterial isolates of Gram-positive cocci or Gram-negative coccobacilli were isolated. In phenotyping, biochemical and molecular (PCR) assays Lactococcus garvieae (12 isolates, 16.2 %), Aeromonas hydrophila (9 isolates, 12.2 %), Streptococcus iniae (17 isolates, 23 %), Streptococcus agalactiae (20 isolates, 27 %), and Yersinia ruckeri (16 isolates, 21.7 %) were identified. The maiority of these isolates were obtained from the fish farms in Mazandaran province. Erythromycin and oxytetracycline with 87.8 % resistance were antibiotics with the highest resistance, while enrofloxacin with 24.3 % resistance revealed the lowest level of resistance. Antibiotic resistance rates for florfenicol and nitrofurantoin were also 43.2 % and 44.4 %, respectively. The highest antibiotic resistance was detected in the bacterial isolates of Lactococcus garvieae, Aeromonas hydrophila, Streptococcus iniae, Streptococcus agalactiae and Yersinia ruckeri, respectively. CONCLUSIONS: This study shows that the spread of streptococcosis, lactococcosis, yersiniasis and Aeromonas septicemia and their frequent treatments has led to an increase in antibiotic resistance, especially against commonly used drugs such as erythromycin and oxytetracycline. [ABSTRACT FROM AUTHOR]

Copyright of Agroindustrial Science is the property of Agroindustrial Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fitness of fish is assumed to be influenced by locomotion performance, but empirical evidence linking swimming capacity to survival in nature remains sparse. Poor triploid (3N) fish aerobic swimming performance in conjunction with production of sibling diploid (2N) and 3N populations of genetically identical origin to minimize variability among compared populations make 3N trout an informative system to test hypotheses about fitness consequences of fish locomotion. Here, we ask if reduced survival of 3N relative to 2N trout in natural ecosystems during periods of high temperature relate to a lower aerobic swimming capacity and aerobic scope of 3N compared with 2N conspecifics. Three-yearly cohorts of conspecific 2N and 3N hatchery-reared, yearling rainbow trout were ranked for swimming endurance, externally marked for their endurance quantile, and then stocked into two lakes as yearlings to quantify their survival in the wild over summer as a function of ploidy, temperature and endurance; all while tracking temperature and depth habitat utilization via telemetry. As expected, 3N swimming endurance was lower than that of 2N, but with considerable individual overlap. Aerobic swimming endurance, especially for 3N, was predictive of summer survival in a warm lake where piscivorous birds potentially exerted high predation pressure, resulting in low fish survival. This empirical evidence of a connection between swimming endurance and fitness provides support for long held assumptions of this relationship and could inform future sport fishing stocking industry practices to match fish strains to ideal habitats. [ABSTRACT FROM AUTHOR]

Behaviour observations of the endangered native marble trout (Salmo marmoratus, Cuvier, 1829) and introduced rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) in the laboratory and in a tributary to the Idrijca River in Slovenia were combined to study the movements and dominance relationships between individuals of the two species in an open field test. Under laboratory conditions, no difference between the species was detected for neither time spent actively or distance moved. In species paired tests, rainbow trout initiated more aggressive behaviours towards marble trout than vice versa, and rainbow trout were clearly the dominant individuals. After simultaneous release in the river, marble trout immediately left the release area and spent twice as long time as rainbow trout until they settled in an area of the river; therefore, the release site was immediately occupied exclusively by rainbow trout. Thus, the dominant and aggressive behaviour of rainbow trout seen in the laboratory before release might have influenced marble trout's subsequent behaviour in the river, by marble trout leaving the areas occupied by rainbow trout and moving to locations further away from the release site. In the field, the marble trout occupied sites individually, whereas rainbow aggregated at a few locations. Rainbow trout showed higher movement activity in the morning compared to marble trout. There was a positive correlation between swimming speed in the laboratory and movement in the field for marble trout but not for rainbow trout. In conclusion, the results in this study support the need to end stocking of rainbow trout in rivers with native marble trout. To better understand the interaction between the species, and to develop efficient management plans to protect the native marble trout, reference behaviours should first be understood, and future research in sites where the two species do not co‐exist is needed. This is especially important for marble trout for which behavioural research and data are lacking. [ABSTRACT FROM AUTHOR]

A comprehensive study of fish diversity, relative and absolute biomass of registered species in Zeta River, Montenegro was accomplished. The data were collected during 2019 from three major ecological sectors of the river. A total of 14 fish species were recorded. The highest relative and absolute biomass were recorded on the Lower Zeta - Bjelopavlići - the lower part of the watercourse. Data presented in this paper shows a dramatic decline in both, the abundance and biomass of trout species from this river. Although in the 2019th river Zeta watercourse in Bjelopavlići Valley was proclaimed as a Park of Nature, we haven't detected any benefits for the fish species, especially for the salmonid ones and their abundance continued with decreasing trend. Most probably the bad practice of poaching with forbidden tools just continued no matter on newly proclaimed protection status. It is shown that proclaiming some area or river in the protected area of any level doesn't benefit to biodiversity if it is not followed with precise management plans and strict implementation. [ABSTRACT FROM AUTHOR]