Human activities and climate change have significantly increased humic substances in freshwater ecosystems over the last few decades. This increase is particularly concerning during seasonal changes or after heavy rainfall, when concentrations can easily increase up to tenfold. This phenomenon, known as "browning," has unknown consequences for aquatic organisms. This study is the first to determine the effects of increasing humic substance concentrations on the transcriptomic and structural responses in the gills of rainbow trout (Oncorhynchus mykiss). Overall, 27 genes mainly involved in xenobiotic metabolism (cyp1a3, cyp1b1, pik3r6), immune response (rgs2, dll1, ccl19, acod1), and mucosal glycoprotein expression (muc2, prg4) were upregulated. No significant alterations were noted in gill morphology, although the molecular data strongly indicated a proinflammatory response. Our results highlight the risks posed by increasing humic substance concentrations for fish and aquatic ecosystems and emphasize the urgent need to implement effective monitoring and resource management strategies to address browning waters.

• Klíčová slova
• Climate change, Increasing dissolved organic carbon, Inflammation, Rainbow trout, Transcriptome analysis,
• MeSH
• benzopyrany * toxicita   MeSH
• chemické látky znečišťující vodu * toxicita   MeSH
• huminové látky * toxicita   MeSH
• Oncorhynchus mykiss * genetika   metabolismus   MeSH
• sladká voda MeSH
• transkriptom * účinky léků   MeSH
• žábry * účinky léků   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• benzopyrany * MeSH
• chemické látky znečišťující vodu * MeSH
• fulvic acid MeSH Prohlížeč
• huminové látky * MeSH

Rainbow trout (Oncorhynchus mykiss) is an important fish species raised in aquaculture, but it is susceptible to stress, infections diseases. The present study aimed to determine the effects of fulvic acid feed addition on the systemic and mucosal protective mechanisms of juvenile rainbow trout and to elucidate the underlying molecular mechanisms of changes in the gut. Rainbow trout (4.30 ± 0.6 g) diet was supplemented with different levels of fulvic acid: 0% (Control), 0.5%, 1% and 2%. At the end of 8-week feeding trial, growth parameters such as final weight gained weight (%), SGR (F1%) increased, and FCR (all levels) decreased significantly compared to the control group. We found that the activity of lysozyme, glutathione peroxidase, and catalase in the serum were significantly improved, especially after the addition of 0.5% and 1% of fulvic acid. At the same time, the immunoglobulin concentration in the skin mucus was increased with 0.5% supplementation. However, the expression of tnf-α, il-6 and gpx in the intestine was strongly upregulated after supplementation with 2%, indicating oxidative stress and inflammation with this level of fulvic acid inclusion. Furthermore, the mucus lysozyme activity was reduced at this concentration, which can increase the susceptibility to pathogen invasion. The results suggest that adding 0.5%-1% of fulvic acid to the feed of juvenile rainbow trout can help to improve their immune and antioxidative defenses and thereby support the wellbeing of fish.

• Klíčová slova
• antioxidant defence, fulvic acid, gene expression, immune response, trout,
• MeSH
• benzopyrany * farmakologie   aplikace a dávkování   MeSH
• dieta veterinární   MeSH
• fyziologie výživy zvířat MeSH
• krmivo pro zvířata * analýza   MeSH
• Oncorhynchus mykiss * fyziologie   růst a vývoj   MeSH
• potravní doplňky MeSH
• regulace genové exprese účinky léků   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• randomizované kontrolované studie veterinární MeSH
• Názvy látek
• benzopyrany * MeSH
• fulvic acid MeSH Prohlížeč

Artificial conditions limit the ability of laboratory studies to describe the complex effects of polluted environments on aquatic life. This study aimed to evaluate the impacts of treated wastewater discharge on the survival, growth, and sex ratio balance of the population of brown trout (Salmo trutta m. fario) in situ. Five floating incubators with 1000 eggs each were placed in the upstream reference and treated wastewater-affected sites in the Czech Republic for approximately three months. The hatched fish were grown in a natural environment for nearly one year. Water quality, including nutrients, temperature, pharmaceutical and personal care products, biological effects by bioassays and fish mortality, metabolic rate, and growth, were measured regularly. Up to 72 pharmaceutical and personal care products (7400-23000 ng/sampler) were detected in the passive samplers deployed downstream of the sewage treatment plant effluent. In vitro bioassays of the sampler extracts indicated elevated oestrogenic effects, transthyretin binding inhibition, and aryl hydrocarbon-mediated and androgenic potencies, showing endocrine-disrupting potential at the polluted site. The cumulated mortality of brown trout in the exposed group (9.67%) was significantly higher (p < 0.05) than in the control group (5.16%). In addition, the body size, growth, and metabolic rate of exposed fish were significantly lower (p < 0.05). The sex ratio of brown trout in the effluent-affected stretch was imbalanced, and sterile individuals were detected after several months of natural development in the stream. The observed effects of treated wastewater on the early developmental stages of aquatic wildlife could be connected to the development and readiness of adult individuals and, consequently, to the sustainability of freshwater ecosystems. Applying the hatching apparatus used in fishery practices, followed by comparing mortality, development, and sex with reference localities, seems to be a promising biomonitoring approach that can indicate hotspots for in-depth investigation and risk assessment.

• Klíčová slova
• Growth change, In situ exposure, Pharmaceutical and personal care products, Population sex ratio, Real exposure scenario, Sewage treatment plant effluent,
• MeSH
• chemické látky znečišťující vodu * toxicita   analýza   MeSH
• endokrinní disruptory toxicita   MeSH
• monitorování životního prostředí MeSH
• odpadní voda * toxicita   MeSH
• poměr pohlaví MeSH
• pstruh * růst a vývoj   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Česká republika MeSH
• Názvy látek
• chemické látky znečišťující vodu * MeSH
• endokrinní disruptory MeSH
• odpadní voda * MeSH

Despite the growing threat of pharmaceutical pollution, we lack an understanding of whether and how such pollutants influence animal behavior in the wild. Using laboratory- and field-based experiments across multiple years in Atlantic salmon (Salmo salar; n = 730), we show that the globally detected anxiolytic pollutant clobazam accumulates in the brain of exposed fish and influences river-to-sea migration success. Clobazam exposure increased the speed with which fish passed through two hydropower dams along their migration route, resulting in more clobazam-exposed fish reaching the sea compared with controls. We argue that such effects may arise from altered shoaling behavior in fish exposed to clobazam. Drug-induced behavioral changes are expected to have wide-ranging consequences for the ecology and evolution of wild populations.

• MeSH
• anxiolytika * toxicita   MeSH
• chemické látky znečišťující vodu * toxicita   MeSH
• migrace zvířat * účinky léků   MeSH
• mozek metabolismus   MeSH
• řeky MeSH
• Salmo salar * fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• anxiolytika * MeSH
• chemické látky znečišťující vodu * MeSH

Exogenous enzymes are used to enhance ingredient digestibility, overall fish growth, and feed utilization; however, different administration methods have not been extensively studied. In this study, a mixture of carbohydrases (α-amylase, cellulase, xylanase, and β-glucanase) was applied before (at B3, B6, B12, and B24 hours), during (D), or after (A) the production of high-carbohydrate diets (33% carbohydrates) to assess their effects on the growth and feed utilization of rainbow trout. The enzymes were added to the diets at the minimum required levels, determined by a reducing sugar test with dinitrosalicylic acid (DNS) based on the available wheat flour and soybean meal in the diet. Seven isoenergetic (21 kJ/g) and isonitrogenous (40%) diets were formulated and fed to fish (n = 210, 17.41 ± 1.76 g) for 8 weeks. Overall growth parameters improved in the B6 and B3 groups, which also showed the lowest FCR values (0.84 and 0.85, respectively) and significantly higher weight gain, PER, and SGR compared to the other treatments. The apparent digestibility of protein, lipid, ash, and dry matter was significantly enhanced in the B3 group. Additionally, DHA and omega-3 fatty acid content increased in B3 (p < 0.05), although no significant differences were observed in fillet contents of EPA and ARA (arachidonic acid) between treatments (p > 0.05). The pretreatment of ingredients (B3 and B6) likely induced a protein-sparing effect, as indicated by higher PER and increased amino acid retention in the fillets (p < 0.05). Moreover, higher metabolizable energy and glucose levels led to significant upregulation of the ghrelin hormone (GHRL), growth hormone (GH), and insulin-like growth factor (IGF-I) genes in the B3 and B6 treatments (p < 0.05). In conclusion, pretreatment of ingredients (soybean meal and wheat flour) with optimized multienzyme doses improved digestibility and activated regulatory genes, resulting in enhanced growth, feed utilization, and fillet quality in high-carbohydrate diets for rainbow trout.

• Klíčová slova
• Exogenous enzymes, Non-protein energy, Plant-based diet, Protein sparing effect, Rainbow trout, Sustainable aquaculture,
• MeSH
• dieta * veterinární   MeSH
• dietní sacharidy * aplikace a dávkování   MeSH
• fyziologie výživy zvířat MeSH
• glykosidhydrolasy * farmakologie   aplikace a dávkování   MeSH
• krmivo pro zvířata analýza   MeSH
• maso * normy   MeSH
• Oncorhynchus mykiss * růst a vývoj   fyziologie   metabolismus   genetika   MeSH
• potravní doplňky MeSH
• regulace genové exprese účinky léků   MeSH
• trávení * účinky léků   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• dietní sacharidy * MeSH
• glykosidhydrolasy * MeSH

Early life experiences have long-lasting effects on behaviour and physiology, influencing development of adaptive natural behaviours. Enriching farmed environments encourages expression of natural behaviours in captive fish, promoting positive animal welfare, important for conducting valid and reproducible research and informing better management practices. Using juvenile Atlantic Salmon (Salmo salar), we tested whether provision of environmental enrichment in early life improves welfare. Welfare indicators were measured comparing enriched to non-enriched tanks. Morphological (fin damage and body condition), physiological (plasma cortisol) and behavioural traits (activity, group cohesion, and neophobia) were recorded. Molecular expression of brain mRNA transcripts related to stress response, neuroplasticity and serotonergic system was analysed. Environmental enrichment did not affect morphological welfare indicators, activity, or cortisol. Enriched fish were more cohesive than non-enriched fish, less neophobic, with higher serotonergic turnover, suggesting enrichment mitigates against stress, promoting positive emotional states. Genes related to neuronal development and activity (bdnf and ndf1), cellular stress (hsp90 and hsp70), and serotonin synthesis (tph2) increased in enriched fish following stress, enhancing cognitive function. Our findings suggest early life environmental enrichment is advantageous for positive animal welfare by improving emotional states in captive environments, ensuring animals are free of negative experiences and able to access positive ones.

• Klíčová slova
• Cognitive abilities, Fish welfare, Neurogenesis, Social behaviour, Structural enrichment,
• MeSH
• chování zvířat MeSH
• fyziologický stres MeSH
• hydrokortison krev   MeSH
• pohoda zvířat * MeSH
• Salmo salar * fyziologie   růst a vývoj   MeSH
• serotonin metabolismus   MeSH
• vodní hospodářství * metody   MeSH
• životní prostředí * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• hydrokortison MeSH
• serotonin MeSH

Salmonid fishes are a widespread and economically important group of fishes that are strongly affected by anthropogenic environmental degradation. Consequently, studies on their behavior and ecology are essential for their conservation. Wild Arctic grayling (Thymallus arcticus) were observed in an unimpacted Alaskan river using underwater video observations for two consecutive summers (2015 and 2016). Foraging, aggressive behavior, and position held by individual fish were quantified. Fish held focal positions in the water column most of the time (mean = 81%), active foraging was observed for 14% of the observation periods, and antagonistic interactions occurred during 5% of the time. The analysis of intraspecific aggression revealed that aggressive interactions occurred between conspecifics of similar sizes (±100 mm), although the winners of bouts were significantly larger than the losers. Notably, initiators emerged as more successful in these bouts compared to receivers, irrespective of body length. These findings underscore the significance of conducting field studies to gain valuable insights into the behavior of fish in their natural stream environments.

• Klíčová slova
• Alaska, aggression, behavior, stream fish, visual observation,
• MeSH
• agrese MeSH
• řeky MeSH
• Salmonidae * fyziologie   MeSH
• stravovací zvyklosti * MeSH
• velikost těla * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Aljaška MeSH

The present study investigated the effects of a feed additive (FA) containing a probiotic consortium, fructooligosaccharide and yeast extract on growth performance, humoral immune responses, hepatic antioxidant parameters and intestine digestive enzymes, morphology and transcripts in rainbow trout, Oncorhynchus mykiss. The fish were reared for 8 weeks, feeding on diets containing 0 (CNT), 0.3 (0.3FA), 1 (1FA) and 2 (2FA) g/kg FA. The results showed that fish growth parameters were significantly and quadratically related to FA levels and FA treatments had better growth performance than CNT treatment. Intestinal amylase activity significantly increased in 2FA, whereas, intestinal protease activity increased in all FA treatments. Intestinal villus length and muscular layer thickness significantly increased in 0.3FA treatment. Blood leucocyte and lymphocyte counts, plasma lysozyme activity and hepatic glutathione content significantly increased in 0.3FA and 1FA treatments; whereas hepatic malondialdehyde significantly decreased in these treatments. Blood neutrophil and monocyte counts significantly increased in 0.3FA treatment, while plasma alternative complement activity significantly increased in 1FA treatments. Plasma bactericidal activities against Aeromonas hydrophila, Yersinia ruckeri and Streptococcus iniae, and intestinal expression of heat shock protein 70 and beta-defensin significantly increased in all FA treatments. The abundance of A. hydrophila, Y. ruckeri and S. iniae in fish gut significantly decreased in 0.3FA treatment; these bacteria were absent in the intestines of 1FA and 2FA treatments. The present results suggest that dietary 0.3-1 g/kg of FA can significantly improve growth performance, immune response, intestinal health and hepatic antioxidant capacity in rainbow trout.

• Klíčová slova
• blood, feed additive, fructooligosaccharide, intestine, lactic acid bacteria,
• MeSH
• dieta veterinární   MeSH
• fyziologie výživy zvířat MeSH
• krmivo pro zvířata analýza   MeSH
• kvasinky * chemie   MeSH
• oligosacharidy * farmakologie   aplikace a dávkování   chemie   MeSH
• Oncorhynchus mykiss * fyziologie   růst a vývoj   MeSH
• potravní doplňky MeSH
• probiotika * farmakologie   MeSH
• střeva účinky léků   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• klinické zkoušky veterinární MeSH
• Názvy látek
• fructooligosaccharide MeSH Prohlížeč
• oligosacharidy * MeSH

Pharmaceutical pollution poses an increasing threat to global wildlife populations. Psychoactive pharmaceutical pollutants (e.g. antidepressants, anxiolytics) are a distinctive concern owing to their ability to act on neural pathways that mediate fitness-related behavioural traits. However, despite increasing research efforts, very little is known about how these drugs might influence the behaviour and survival of species in the wild. Here, we capitalize on the development of novel slow-release pharmaceutical implants and acoustic telemetry tracking tools to reveal that exposure to environmentally relevant concentrations of the benzodiazepine pollutant temazepam alters movement dynamics and decreases the migration success of brown trout (Salmo trutta) smolts in a natural lake system. This effect was potentially owing to temazepam-exposed fish suffering increased predation compared with unexposed conspecifics, particularly at the river-lake confluence. These findings underscore the ability of pharmaceutical pollution to alter key fitness-related behavioural traits under natural conditions, with likely negative impacts on the health and persistence of wildlife populations.

• Klíčová slova
• behaviour, chemical, ecology, global change, survival, telemetry,
• MeSH
• chemické látky znečišťující vodu * toxicita   MeSH
• jezera * MeSH
• migrace zvířat * MeSH
• pstruh * fyziologie   MeSH
• psychotropní léky farmakologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chemické látky znečišťující vodu * MeSH
• psychotropní léky MeSH

Tapeworms of the genus Proteocephalus Weinland, 1858 (Cestoda: Proteocephalidae) are common and widespread intestinal parasites of whitefish (Coregonus spp., Salmonidae: Coregoninae). Previous taxonomic studies, based solely on morphology and inconsistently fixed specimens, concluded that all salmoniform fish, including whitefish, are parasitised by a single euryxenous and highly polymorphic species, Proteocephalus longicollis (Zeder, 1800). However, recent molecular phylogenetic analyses have revealed the existence of several species specific to individual genera or even species of salmoniform fish. In this study, Proteocephalus fallax La Rue, 1911 is redescribed based on newly collected and genetically characterised specimens from several Coregonus species in Switzerland, the type locality of the species, and in Norway. This cestode was previously synonymised with P. exiguus La Rue, 1911, a parasite of whitefish in North America, but the two species are not closely related. Proteocephalus fallax differs from P. exiguus in its larger body size, wider proglottids, shorter cirrus sac and broader scolex. In addition, the other Proteocephalus species described in whitefish are briefly discussed, with comments on their validity, host range and distribution.

• Klíčová slova
• Eucestoda, Europe, Proteocephalidae, Salmonidae, distribution, morphology, taxonomy,
• MeSH
• Cestoda * klasifikace   anatomie a histologie   izolace a purifikace   MeSH
• cestodózy * veterinární   parazitologie   MeSH
• fylogeneze * MeSH
• nemoci ryb * parazitologie   MeSH
• Salmonidae * parazitologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Norsko MeSH
• Švýcarsko MeSH