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The exposure of adult fish to warm or high temperatures is known to impair reproduction, yet the long-term reproductive impacts for treatments at early life are not well clarified. This study aimed to evaluate the effects of warm temperature (WT) during juvenile stage on gonad maturation, gamete quality, and offspring thermotolerance in rainbow trout. While the comparison of basic reproductive parameters in WT females did not reveal any kind of impairment, many WT males showed an atrophied, undeveloped gonad, or a smaller testis with lower milt volume; sperm quality parameters in WT males and deformity rates in the respective progeny were also highly affected. However, despite of such negative effects, many of the remaining progeny presented better rates of survival and growth when exposed to the same conditions as those of parental fish (WT), suggesting that thermal stress in parr stage males elicited intergenerational thermotolerance after a single generation. The present results support that prolonged warming stress during early life stages can adversely affect key reproductive aspects, but contrastingly increase offspring performance at upper thermal ranges. These findings have implications on the capacity of fish to adapt and to cope with global warming. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate the effects of dietary vitamin E, nanoselenium (nanoSe), and their combination on growth and acute stress responses in rainbow trout previously subjected to chronic stress. The fish were divided into five groups according to stocking density and diet: Normal (20 kg m − 3 ; basal diet), Dense (80 kg m − 3 ; basal diet), Vit E (80 kg m − 3 ; 500 mg kg − 1 vitamin E-supplemented diet), NanoSe (80 kg m − 3 ; 1 mg kg − 1 nanoSe-supplemented diet), and Combination (80 kg m − 3 ; 500 mg kg − 1 vitamin E and 1 mg kg − 1 nanoSe-supplemented diet). The fish in each group were weighed after 60 days. The best growth under high density condition was observed in fish fed on vitamin E-supplemented diets (Vit E and Combination groups). Following high stocking rearing, fish were subjected to an acute confinement stress by decreasing water volume in the tanks (200 kg fish m − 3 ) for 45 min and sampled at 0, 2, 4, 8 and 24 h post-stress to evaluate the fish performance to additional stressors. The levels of serum cortisol, glucose, lactate, alanine aminotransferase, aspartate transaminase, and alkaline phosphatase were significantly higher in the Dense group at most of time points after initiation of acute stress. The results showed that rainbow trout can reach adaptation to chronic stress conditions, resulting in intensified stress responses to an acute stressor. The data also showed that vitamin E-supplemented diets can exert positive effects on the welfare of chronically stressed rainbow trout subjected to an additional acute stressor. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of live transport of rainbow trout and subsequent live storage in an outlet aquarium on water quality, animal welfare and stress. A total of 40 fish were sampled at the following steps in the process: (1) at the raceway before transport, (2) after transport (arrival at fish outlet), (3) 24 h after fish were transferred to outlet aquarium (market), and finally, (4) after 48 h storage in the aquarium. Blood samples were collected from 10 fish at each stage and the levels of plasma cortisol, electrolytes (Na ⁺, K ⁺, Clˉ), and whole blood lactate were assessed. Twitch ability, initial pH, and temperature were assessed in white muscle. Respiration rate and swimming behavior were also assessed while the fish were kept in the outlet. Water quality (temperature, pH, dissolved oxygen, total ammonium nitrogen, total organic carbon, alkalinity and color) were assessed along with all stress measurements. Compared with fish at the farm, live transport, including effects of loading and unloading, represented the main stressor in our study. Heavy oxygen supersaturation, possibly along with elevated levels of carbon dioxide during transport contributed to this result. Despite sub-optimal water quality and excessive respiration rates, the fish in the aquarium seemed to slowly recover after transport. To reduce the effects of stress and improve animal welfare, it is suggested to minimize air exposure time and to avoid exposing the fish to supersaturated and sub-optimal levels of dissolved oxygen. Statement of relevance In a European context, selling live salmonids in the market is unusual. In this way, the highest possible freshness can be assured. However, live transport in closed systems and the live storage in fish outlets can imply risks related to compromised animal welfare and excessive stress as well as possible mortalities. In the present MS we looked into the how present handling routines and water quality affected the fish (behavior, stress and welfare). Possible improvements of present routines are discussed. We are not familiar with other published papers covering such a value chain for salmonids. [ABSTRACT FROM AUTHOR]

Cortisol is the main biomarker of physiological stress in fish. It is usually measured in plasma, which requires blood collection. Though cortisol is produced in the anterior kidney, it can diffuse easily through cell membranes due to its lipophilic nature. Taking advantage of that, some non-invasive techniques have been developed to measure cortisol directly in the water from fish-holding tanks, in skin mucus or in scales. In this study, we explored the possibility to analyze fish cortisol from gill filaments as a reliable acute stress marker. Our results show that gill cortisol levels correlate well with plasma cortisol levels in both rainbow trout and zebrafish exposed or not to an acute stress protocol. Measuring cortisol in gill filaments increases the available possibilities for stress assessment in fish. Although this approach should yet be tested for its use with other stressors, it has several advantages: In relatively large fish (i.e. above 30 g) gill cortisol levels could be measured in vivo . Sampling of gill biopsies is very fast and easy, and the procedure does not induce stress if properly performed, making it an ideal option for in vivo stress assessment. In small fish, the use of gill tissue to measure cortisol has important technical advantages with respect to the current methods using whole-body homogenates. Gill homogenates could be used directly for ELISA cortisol analysis, avoiding the need of tedious and expensive cortisol extraction protocols, and, since no organic solvent is required, contributing for a more environmentally friendly analysis. [ABSTRACT FROM AUTHOR]

Effects of four different fiberglass tank colors i.e. beige, grey, dark green and light green on growth performance of rainbow trout (Oncorhynchus mykiss) juveniles (4.88±0.71 g) were investigated in this study. The study lasted for 60 days and was conducted under actual culture conditions in a commercial trout farm using spring water with an average temperature of 14.8 oC. Growth performance of fish was evaluated in light of criteria such as mean final weight, specific growth rate (SGR), feed conversion ratio (FCR), energetic growth efficiency (EG), condition factor (K) and survival rate (SR). Mean final weight of fish in beige colored tanks reached 76.26 ± 10.52 g while mean final weights of fish in grey, dark and light green tanks were measured as 64.95 ± 6.94, 69.44 ± 8.81 and 68.87 ± 6.42 g, respectively. The differences between mean final weight of fish in 4 experimental groups were found to be statistically significant (P<0.05). However, no significant differences were found in terms of growth performance criteria among 4 experimental groups (P>0.05). Highest live weight gain (71.38 g), SGR (4.58% day-1), EG (45.25%) and condition factor (1.14) as well as lowest FCR (0.90) were recorded in beige colored tanks. The poorest values of growth performance criteria were observed in fish kept in grey tanks, while fish in dark and light green tanks showed similar performances. Survival rates in experimental groups were similar and varied between 98.25% and 99.57%. In conclusion it can be specified that under culture condition employed in this study and especially under low light intensities beige colored tanks are more suitable for rearing of rainbow trout fry. [ABSTRACT FROM AUTHOR]

: Fish under intensive rearing conditions experience various stressors which have negative impacts on survival, growth, reproduction and fillet quality. Identifying and characterizing the molecular mechanisms underlying stress responses will facilitate the development of strategies that aim to improve animal welfare and aquaculture production efficiency. In this study, we used RNA-seq to identify transcripts which are differentially expressed in the rainbow trout liver in response to handling and confinement stress. These stressors were selected due to their relevance in aquaculture production. Total RNA was extracted from the livers of individual fish in five tanks having eight fish each, including three tanks of fish subjected to a 3 hour handling and confinement stress and two control tanks. Equal amount of total RNA of six individual fish was pooled by tank to create five RNA-seq libraries which were sequenced in one lane of Illumina HiSeq 2000. Three sequencing runs were conducted to obtain a total of 491,570,566 reads which were mapped onto the previously generated stress reference transcriptome to identify 316 differentially expressed transcripts (DETs). Twenty one DETs were selected for qPCR to validate the RNA-seq approach. The fold changes in gene expression identified by RNA-seq and qPCR were highly correlated (R2 = 0.88). Several gene ontology terms including transcription factor activity and biological process such as glucose metabolic process were enriched among these DETs. Pathways involved in response to handling and confinement stress were implicated by mapping the DETs to reference pathways in the KEGG database. Accession Numbers: Raw RNA-seq reads have been submitted to the NCBI Short Read Archive under accession number SRP022881. Customized Perl Scripts: All customized scripts described in this paper are available from Dr. Guangtu Gao or the corresponding author. [ABSTRACT FROM AUTHOR]

Abstract: Lycopene, the major carotenoid found in tomato, exhibits health beneficial effects by virtue of its antioxidant activity. As stocking density is known as a stress factor in fish, the effects of dietary lycopene supplementation (0, 200 or 400mgkg−1) on growth performance and antioxidant status in rainbow trout under normal (20kgm3−1) and high (100kgm3−1) stocking density were studied. Glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) activities were evaluated, as well as lipid peroxidation measured as malondialdehyde (MDA). Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), erythroid-derived 2-like 2 (Nrf2) and heme-oxygenase 1 (HO-1) levels were also assayed as an indicator of detoxifying/antioxidant defense mechanisms to cope with oxidative stress. Results showed that exposure to high stocking density depressed feed intake by 6.8% and body weight gain by 12.1%, increased plasma and hepatic MDA level by 88.5 and 124.3% and decreased hepatic SOD, CAT and GSH-Px activities by 22.1, 43.4 and 51.7%, respectively. In fish under crowded conditions, an expression of hepatic NF-κB was increased by 71.5%, being suppressed in Nrf2 and HO-1 by 40.6 and 42.7%, respectively. Lycopene supplementation increased linearly fish growth performance and antioxidant enzyme activity, and decreased linearly MDA concentration in both low and high stocking densities. NF-κB levels decreased hepatic Nrf2 and HO-1 levels increased linearly with lycopene supplementation at a greater extent in fish under low stocking condition. In conclusion, dietary supplementation of lycopene to fish reduces the detrimental effects of high stocking density on growth performance and modulates oxidative status via activating host defense system at cellular level. It appears that lycopene can be added up to 400mgkg−1 to rainbow trout diets to improve meat quality. [Copyright &y& Elsevier]

Abstract: The effects of dietary probiotics on growth performance, health status of the digestive system and on the blood parameters of juvenile rainbow trout (Oncorhynchus mykiss, Walbaum) were investigated. Compared to the controls, diets supplemented with Kocuria SM1 and Rhodococcus SM2 for 14days caused no significant (P>0.05) change on the growth of fish, although SM2 led to an increased specific growth rate. SM1 or SM2 started to colonize in the gut after 7days of administration reaching a maximum, i.e. ~90–100% of total bacterial population, at 14days. Yet, the probiotics disappeared from the gut once administration ceased. Structural differences were not noted in the pyloric caeca and foregut, but the overall condition of the midgut and hindgut improved in fish receiving probiotics. The profile of digestive enzymes, as determined by the use of API ZYM, and stress indicators, i.e. serum hemoglobin, urea, creatinine and glucose, was not affected by any of the experimental diets (P>0.05). [Copyright &y& Elsevier]

The brain monoaminergic neurotransmitter systems are known to be involved in the integrated response to stress in vertebrates. However, present knowledge about the timing of their actions as well as their specific roles in the regulation of the endocrine axes that drive the stress response is incomplete. This is partly because of the complexity of the reciprocal interactions among the monoaminergic systems and other biochemical effectors of the stress response such as corticotropin-releasing factor (CRF), arginine vasotocin (AVT), adrenocorticotropic hormone (ACTH) and corticosteroids. In this study, we show for the first time in teleost fish (rainbow trout) the short- and mid-term time course of the response of the forebrain serotonergic and dopaminergic activities after exposure to an acute stressor. Other stress markers like the plasma levels of cortisol, glucose and lactate were also monitored, providing a context in which to precisely locate the monoaminergic activation within the fish acute stress response. Our results show that acute stress induced a rapid increase in forebrain serotonergic activity, which became elevated after only 15 s of chasing. Several hours after stress, serotonergic activity recovered its basal levels, in parallel with the recovery of other stress markers such as plasma catecholamines and cortisol. Dopaminergic activity was also increased after stress, but only in the telencephalon and only after 20 min. The increase in serotonergic activity happened before the elevation of plasma catecholamines, suggesting that this monoamine system could have a key role in triggering the initial steps of the activation of not only the hypothalamus-pituitary-inter-renal axis but also the brain-sympathetic-chromaffin axis in fish. [ABSTRACT FROM AUTHOR]

The influence of light colours on growth and stress response in rainbow trout Oncorhyncus mykiss (15.16 ± 0.29 cm; 32.27 ± 1.18 g) was studied. Fish were reared in 16 glass aquaria (140 × 30 × 80 cm) each with 12 fish under one of four different lighting spectra: yellow (546 nm), red (605 nm), blue (470 nm) and white (full spectrum, control). Experiments lasted 125 days. The stress response was evaluated by measuring cortisol levels. Body weight and total length of the fish reared under yellow light were greater compared with the other colour regimes while feed conversion ratio significantly lowers. Condition factor and specific growth rate, however, were not differentiated among experimental light treatments. Stressed fish showed lower cortisol levels under yellow light compared with other light exposures. The study indicates that under laboratory conditions, rainbow trout grow best under yellow light and that yellow light lowers the stress-induced cortisol response in this fish species. [ABSTRACT FROM AUTHOR]

Abstract: Boldness, a measure of an individual''s propensity for taking risks, is an important determinant of fitness but is not necessarily a fixed trait. Dependent upon an individual''s state, and given certain contexts or challenges, individuals may be able to alter their inclination to be bold or shy in response. Furthermore, the degree to which individuals can modulate their behaviour has been linked with physiological responses to stress. Here we attempted to determine whether bold and shy rainbow trout, Oncorhynchus mykiss, can exhibit behavioural plasticity in response to changes in state (nutritional availability) and context (predation threat). Individual trout were initially assessed for boldness using a standard novel object paradigm; subsequently, each day for one week fish experienced either predictable, unpredictable, or no simulated predator threat in combination with a high (2% body weight) or low (0.15%) food ration, before being reassessed for boldness. Bold trout were generally more plastic, altering levels of neophobia and activity relevant to the challenge, whereas shy trout were more fixed and remained shy. Increased predation risk generally resulted in an increase in the expression of three candidate genes linked to boldness, appetite regulation and physiological stress responses - ependymin, corticotrophin releasing factor and GABAA - but did not produce a significant increase in plasma cortisol. The results suggest a divergence in the ability of bold and shy trout to alter their behavioural profiles in response to internal and exogenous factors, and have important implications for our understanding of the maintenance of different behavioural phenotypes in natural populations. [Copyright &y& Elsevier]

Behavioural endocrinologists have shown that stressors including competition for resources can affect an individual’s circulating level of cortisol, whereas agonistic interactions typically affect androgen levels. Conservation biologists have used such data to facilitate the restoration and management of biodiversity by monitoring social interactions and stress among individuals and species. Here, we examined whether competition and agonistic interactions with non-native salmonids is hindering restoration of native Atlantic salmon, Salmo salar, in Lake Ontario. Using semi-natural streams, we examined the effects of competition with non-native brown trout, Salmo trutta, and rainbow trout, Oncorhynchus mykiss, on plasma cortisol and 11-ketotestosterone (11-KT) concentrations in juveniles from three Atlantic salmon strains, as well as the relationship between these hormones and social dominance and growth. Basal hormone levels and the hormonal response to the presence of the trouts varied among the strains. Cortisol increased in the presence of the trouts for two strains and was associated with lowered aggression and food consumption. Conversely, the presence of the non-native species had little influence on overall concentrations of 11-KT in the Atlantic salmon, although unexpectedly, there was a negative relationship between 11-KT and initiated aggression when either one of the trouts was present. Interestingly, elevated 11-KT levels were associated with declines in both food consumption and growth. Overall, our results suggest that competition with non-native salmonids negatively impacts Atlantic salmon. We discuss how our results can improve poststocking success and restoration of Atlantic salmon in Lake Ontario. [Copyright &y& Elsevier]

A primary culture system of rainbow trout gill pavement cells grown on permeable support (single-seeded insert, SSI) was used to examine histological and physiological changes induced by the addition of the corticosteroid hormone cortisol. Pavement cell epithelia were cultured under symmetrical conditions (L15 apical/L15 basolateral) and developed a high transepithelial resistance (TER, 6.84 ± 1.99 kΩ cm, mean ± SEM) with a low phenol red diffusion rate (PRD, 0.15 ± 0.03 μmol l/day). Addition of cortisol to the basolateral compartment increased TER twofold and reduced PRD threefold over a 5-day period. A similar increase in TER could be seen after 24 h apical freshwater (FW) in control cultures. In cortisol-treated cultures FW exposure did not change TER, but PRD increased significantly. Histochemical staining of the cytoskeleton of cells in SSI culture revealed a morphological partitioning into a single mucosal layer of polarized, polygonal cells featuring cortical F-actin rings which were comparable to F-actin rings of epithelial cells on the lamellar and filamental surface, and several unorganized serosal layers of cells with F-actin stress fibers. Addition of cortisol increased cell density by 18% and in the mucosal layer it led to smaller, less polygonal cells with increased height and increased cell contact area. In transmission electron microscopic images two pairs of cytoplasmatic electron-dense structures confining the zonula occludens apically and basally toward the zonula adhaerens were found. Addition of cortisol increased the distance between those paired structures, hence led to deeper tight junctions. The cortisol-induced increase in barrier properties, therefore, involves a structural fortification of the tight junctions which was not generally modified by a short 24-h apical freshwater stress. These results identify cortisol as a regulator of tight junction morphology between pavement cells of euryhaline fish such as the trout. [ABSTRACT FROM AUTHOR]

Abstract: Two divergent behavioural and physiological response patterns to challenges have been identified in mammals and birds, frequently termed the proactive and reactive coping styles. In recent years, individually distinct coping styles have also been observed in several species of fish. These individual differences may result in suboptimal production and compromised welfare in aquaculture. An approach to overcome these problems could be to sort fish and optimise rearing conditions according to coping style. It has been previously demonstrated that the proactive and reactive coping styles in fish can be characterised by contrasting behavioural responses to hypoxia. Two rainbow trout (Oncorhynchus mykiss) strains, bred for a low- (LR) and high- (HR) cortisol response to a standardized stressor, are suggested to resemble the proactive and reactive coping styles respectively. Therefore, these fish provided an opportunity for verifying a method for sorting fish with respect to coping style by exposure to hypoxia. Groups consisting of 24 individually tagged fish, 12 HR and 12 LR were exposed to hypoxia in a two choice system. The system consisted of a “home” tank provided with cover connected to a second brightly “illuminated” tank via a closable doorway. During the experiment, the doorway between the two tanks was opened and hypoxic conditions were gradually induced in the “home” tank by bubbling with nitrogen. The latency time to move away from hypoxic conditions to normoxic conditions in the second tank was recorded for each individual. The oxygen saturation in each tank was measured every 30min. The experiment consisted of two trials. Each trial was carried out in two sessions, switching the “home” tank and “illuminated” tank between Sessions 1 and 2. The results indicated that the response to hypoxia differed significantly between LR and HR individuals in both Session 1 (P <0.05) and Session 2 (P ≤0.001). Furthermore, a higher number of HR individuals left hypoxic conditions compared to LR individuals in both Session 1 (P =0.001) and Session 2 (P ≤0.001). Taken together, the findings of the present study demonstrate a repeatable difference in behavioural response to hypoxia between the two strains. The method presented could be utilized as a non-invasive method for sorting fish according to stress coping style. [Copyright &y& Elsevier]

Abstract: In rainbow trout (Oncorhynchus mykiss), selection for divergent post-stress plasma cortisol levels has yielded low (LR)- and high (HR) responsive lines, differing in behavioural and physiological aspects of stress coping. For instance, LR fish display prolonged retention of a fear response and of previously learnt routines, compared to HR fish. This study aims at investigating putative central nervous system mechanisms controlling behaviour and memory retention. The stress hormone cortisol is known to affect several aspects of cognition, including memory retention. Cortisol acts through glucocorticoid receptors 1 and 2 (GR1 and 2) and a mineralcorticoid receptor (MR), all of which are abundantly expressed in the salmonid brain. We hypothesized that different expressions of MR and GRs in LR and HR trout brains could be involved in the observed differences in cognition. We quantified the mRNA expression of GR1, GR2 and MR in different brain regions of stressed and non-stressed LR and HR trout. The expression of MR was higher in LR than in HR fish in all brain parts investigated. This could be associated with reduced anxiety and enhanced memory retention in LR fish. MR and GR1 expression was also subject to negative regulation by stress in a site-specific manner. [Copyright &y& Elsevier]

Abstract: The objective of the study was to examine the impact of municipal wastewater effluents on the functioning of the cortisol stress axis in rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout were caged upstream (reference) and downstream (100% and 10% effluent) of a tertiary-treated municipal wastewater treatment plant outfall and sampled at 14d later (0 time samples). A second set of fish were then subjected to a 5min handling disturbance and sampled at 1 and 24h post-stressor exposure. Plasma cortisol, glucose and lactate concentrations, liver and brain glucocorticoid receptor (GR) protein levels, head kidney mRNA abundances of corticosteroidogenesis genes, including steroidogenic acute regulatory protein (StAR), cytochrome P450 side chain cleavage (P450scc), 11β-hydroxylase and melanocortin 2 receptor (MC2R), and key liver metabolic enzyme activities, were measured. Exposure to effluent for 14d significantly elevated plasma cortisol and lactate levels in 100% effluent group compared to the reference and 10% effluent sites. There was a significantly higher StAR mRNA abundance in the effluent groups compared to the upstream control. GR protein levels in the liver, but not the brain, were significantly higher in the 100% effluent group compared to the upstream control group. Chronic exposure to 100% effluent for 14d significantly lowered liver hexokinase and glucokinase activities, but did not affect glycogen content or the activities of phosphoenolpyruvate carboxykinase, pyruvate kinase, lactate dehydrogenase, aspartate aminotransferase and alanine aminotransferase compared to the other two groups. Subjecting these fish to a secondary acute stressor elicited a physiological stress response, including significant transient elevation in plasma cortisol, glucose and lactate levels at 1h which dropped to pre-stress levels at 24h after stressor exposure, in the control and 10% effluent groups, but this conserved stress response was impaired in the 100% effluent group. The 100% effluent group fish also had significantly higher StAR and P450scc mRNA abundances at 1h post-stress, while transcript abundances of all the major corticosteroidogenesis genes were suppressed at 24h post-stressor compared to the control and 10% effluent groups. Considered together, exposure to full-strength MWWE for 14d elicits a chronic stress response in rainbow trout, and perturbs the conserved adaptive response to an acute stressor. Our results reveal that the impact of tertiary-treated MWWE on stress performance in rainbow trout is abolished by 90% effluent dilution. [Copyright &y& Elsevier]

Abstract: Among species, various strategies in metal handling can occur. Moreover, the same metal concentration, or even the same metal dose, does not always seem to exert the same effect in different species. Here, we have investigated differences in a copper induced oxidative stress response between rainbow trout (Oncorhynchus mykiss), common carp (Cyprinus carpio) and gibel carp (Carassius auratus gibelio). Fish were exposed to two sub-lethal Cu concentrations, an identical concentration of 50μg/l for all fish species and an identical toxic dose which was 10% of the concentration lethal to 50% of the fish within 96h of exposure (LC50 96h value) for each of the 3 species (20μg/l for rainbow trout, 65μg/l for carp and 150μg/l for gibel carp). Different anti-oxidative enzyme (superoxide dismutase, glutathione reductase and catalase) activities and anti-oxidant (reduced glutathione and reduced ascorbate) concentrations were determined in gill samples collected after 1h, 12h, 24h, 3 days, 1 week and 1 month of Cu exposure. Changes in the measured parameters were present in all 3 species, yet a clear differentiation between fish species could be made before and during the exposure. The ascorbate levels of gibel carp were twice as high as those in common carp or rainbow trout. In contrast, the level of glutathione in rainbow trout was more than twice of that in the two other species. Also, glutathione reductase activity of rainbow trout was higher than in the other species. In rainbow trout a decrease of reduced ascorbate and reduced glutathione was observed in the beginning of the exposure, indicating that ROS scavenging molecules were under pressure. This was followed by an increase in the activity of superoxide dismutase after 3 days of exposure. In contrast, common carp and especially gibel carp enhanced their anti-oxidant enzyme activities as quickly as in the first day of exposure. Furthermore, our research seems to confirm that some fish rely more on glutathione as a first line of defence against metal exposure, while others rely more on metallothionein in combination with anti-oxidant enzymes. [Copyright &y& Elsevier]

Abstract: The aim for this study was to examine whether the F4 generation of two strains of rainbow trout divergent in their plasma cortisol response to confinement stress (HR: high responder or LR: low responder) would also differ in stress-induced effects on forebrain concentrations of mRNA for corticotropin-releasing factor (CRF), arginine vasotocin (AVT), CRF receptor type 1 (CRF-R1), CRF receptor type 2 (CRF-R2) and AVT receptor (AVT-R). In addition, plasma cortisol concentrations, brainstem levels of monoamines and monoamine metabolites, and behaviour during confinement were monitored. The results confirm that HR and LR trout differ in their cortisol response to confinement and show that fish of these strains also differ in their behavioural response to confinement. The HR trout displayed significantly higher locomotor activity while in confinement than LR trout. Moreover, following 180min of confinement HR fish showed significantly higher forebrain concentrations of CRF mRNA than LR fish. Also, when subjected to 30min of confinement HR fish showed significantly lower CRF-R2 mRNA concentrations than LR fish, whereas there were no differences in CRF-R1, AVT or AVT-R mRNA expression between LR and HR fish either at 30 or 180min of confinement. Differences in the expression of CRF and CRF-R2 mRNA may be related to the divergence in stress coping displayed by these rainbow trout strains. [ABSTRACT FROM AUTHOR]

The article features the research regarding the impact of stress on rainbow trout, Oncorhynchus mykiss, in Hungary. When researchers transported the fish in water with anesthetic clove oil, they noticed no vital increases in glucose and cortisol concentration of its blood plasma, but when they removed the fish from the water with anesthetic, its blood plasma increased tremendously. With these data at hand, they concluded that transportation stress can be decreased using anesthetics.

Abstract: This study set out to investigate whether differential expression of genes for acute phase proteins in rainbow trout (Oncorhynchus mykiss) could be induced by confinement stress, a non-invasive method of activating the neuroendocrine stress response. In addition, a second objective was to assess the variation in gene expression between individual fish within the population of stressed fish in an attempt to identify APP genes having uniform and consistent changes in expression during stress. The liver was chosen for this investigation as it is the primary site of acute phase protein synthesis. Relative expression of the eight genes including transferrin, fibrinogen-like protein 2 (flp2), α-1-anti-proteinase-like protein (α1-antiprot), leukocyte cell-derived chemotaxin 2 (LECT2), pentraxin, serum amyloid A (SAA), haptoglobin (Hp), and differentially regulated trout protein 1 (DRTP1) was analysed by quantitative real-time PCR (qPCR) over 5 experimental time points spanning the course of a week. The results showed that the expression of three genes, SAA, haptoglobin and DRTP1, were most altered as a result of exposure to confinement stress. A correlation was identified between the expression of haptoglobin and DRTP1. Gene expression analyses in individual fish found that the transcript levels of haptoglobin and DRTP1 genes varied much less between individuals than was the case for SAA. The increase of haptoglobin and DRTP1 gene expression and its uniformity in response to stress make these genes potential biomarkers for stress in trout. [Copyright &y& Elsevier]

Abstract: Intensive aquaculture systems, particularly recirculating systems, utilize equipment such as aerators, air and water pumps, blowers, and filtration systems that inadvertently increase noise levels in fish culture tanks. Sound levels and frequencies measured within intensive aquaculture systems are within the range of fish hearing, but species-specific effects of aquaculture production noise are not well defined. Field and laboratory studies have shown that fish behavior and physiology can be negatively impacted by intense sound. Therefore, chronic exposure to aquaculture production noise could cause increased stress, reduced growth rates and feed conversion efficiency, and decreased survival. The objective of this study was to provide an in-depth evaluation of the long term effects of aquaculture production noise on the growth, condition factor, feed conversion efficiency, and survival of cultured rainbow trout, Oncorhynchus mykiss. Rainbow trout were cultured in replicated tanks using two sound treatments: 117 dB re 1 μPa RMS which represented sound levels lower than those recorded in an intensive recycle system and 149 dB re 1 μPa RMS, representing sound levels near the upper limits known to occur in recycle systems. To begin the study mean fish weights in the 117 and 149 dB tanks were 40 and 39 g, respectively. After five months of exposure no significant differences were identified between treatments for mean weight, length, specific growth rates, condition factor, feed conversion, or survival (n =4). Mean final weights for the 117 and 149 dB treatments were 641±3 and 631±10 g, respectively. Overall specific growth rates were equal, i.e. 1.84±0.00 and 1.84±0.01%/day. Analysis of growth rates of individually tagged rainbow trout indicated that fish from the 149 dB tanks grew slower during the first month of noise exposure (p <0.05); however, fish acclimated to the noise thereafter. This study further suggests that rainbow trout growth and survival are unlikely to be affected over the long term by noise levels common to intensive aquaculture systems. [Copyright &y& Elsevier]

Cortisol, the principal corticosteroid in teleosts, is thought to play a key role in the metabolic adjustments critical for regaining homeostasis. However, the target tissue molecular mechanisms involved in this adaptive response to corticosteroid stimulation are still unclear. Cortisol signaling is mediated predominantly by the glucocorticoid receptor (GR), and previous studies have shown that RU486 (a GR antagonist) offsets corticosteroid signaling in teleosts. To elucidate the molecular basis of GR-mediated metabolic readjustments, we exposed primary culture of trout hepatocytes in vitro to cortisol (to mimic stressed levels seen in fish), RU486, or a combination of both for 24 h. The gene expression was analyzed using a low-density custom-made rainbow trout cDNA array enriched with endocrine-, metabolic-, and stress-related genes. The microarray results for select genes were further validated using quantitative real-time PCR. Cortisol treatment significantly increased glucose production in hepatocytes, and this response was blocked by RU486, confirming GR-mediated corticosteroid signaling. Cortisol also elevated GR transcript levels, and this response was abolished by RU486, whereas both cortisol and RU486, either alone or in combination, reduced GR protein content in trout hepatocytes. Cortisol treatment significantly modulated the expression of several genes known to be involved in intermediary metabolism, cellular stress response, reproduction, and xenobiotic metabolism. Most of these cortisol-mediated transcript changes were abolished in the presence of RU486, suggesting a key role for GR-specific signaling in this adaptive response. Taken together, our results suggest a key role for genomic cortisol signaling in the liver molecular reprogramming that is critical for coping with stress in fish. [ABSTRACT FROM AUTHOR]

The National Center for Cool and Cold Water Aquaculture is conducting a selective breeding program to improve the germplasm of rainbow trout Oncorhynchus mykiss for aquaculture. Two lines are being selected for improved growth. We previously found a positive correlation between stress responsiveness, indicated by plasma cortisol concentration after a 3-h confinement stressor, and growth performance, indicated by body weight at selection (approximately 300 d posthatching [dph]), in families from the first line. This correlation is confirmed for the second line in the present study. In addition to stressor-induced cortisol levels, resting plasma growth hormone (GH), insulin-like growth factor-I (IGF-I), and cortisol concentrations were measured in the second line as a first step in determining the physiological and genetic bases for growth performance variation and the association between stress responsiveness and growth performance in our germplasm. Hormone levels were compared against two measures of growth: body weight and thermal growth coefficient (TGC). Plasma concentrations of IGF-I and GH in resting fish were not correlated with stress responsiveness and thus provided no link between stress responsiveness and the growth regulatory axis. The TGC was negatively correlated with resting plasma GH and cortisol and positively correlated with IGF-I, whereas only GH was correlated with body weight at 297 dph. Our results suggest that the variation in growth performance among our broodstock families is explained, in part, by variations in resting levels of the growth regulatory and stress axes. In addition, TGC more accurately predicted future growth--body weight at 459 dph--than did body weight at 297 dph. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine whether exposure of rainbow trout ( Oncorhynchus mykiss) to water containing a stressed trout or skin extract from stressed and non-stressed trout would elicit a stress response in conspecifics. Juvenile rainbow trout were exposed for 1 hour to water containing a stressed fish, homogenized skin extracts from a non-stressed fish, skin extract from a stressed fish and water with none of these factors. The stress response was measured over a 24-h period (1, 6, 12, 24 h after exposure). Plasma cortisol levels increased at 12 h in fish exposed to water from a stressed fish and skin extract from a stressed fish. Plasma glucose and hepatic hsp70 levels were not affected by treatments. The results suggest that rainbow trout elicit a stress response when exposed to stress-related alarm cues released from conspecifics. [ABSTRACT FROM AUTHOR]

Abstract A number of indicators of reproductive performance were assessed in rainbow trout divergently selected on the basis of their plasma cortisol response to a standardized stressor. For both male and female rainbow trout Oncorhynchus mykiss (Walbaum), body weight was significantly related to stress responsiveness. High-responding (HR) females were significantly heavier than low-responding (LR) females overall, and HR males were significantly heavier than LR males overall. There was no significant difference in the specific growth rate (SGR) of HR and LR female fish during the experimental period, whereas in contrast the mean SGR of HR males was significantly greater than that of LR males. The divergent confinement-induced levels of blood cortisol in HR and LR groups were stable for more than 1 year after selection. There was no significant difference in the extent to which confinement stress reduced blood oestradiol-17β levels in HR and LR females, despite a large difference in relative blood cortisol levels. The onset and rate of ovulation was similar within the HR and LR groups. Differences in fecundity, relative fecundity and egg volume and weight were wholly attributable to the different mean body weights of the HR and LR fish. There was no difference between the sperm counts of HR and LR males. There was significantly higher mortality among eggs derived from HR parents overall between fertilization and hatch, but maximum mean mortality did not exceed 12%. Mean time to eyeing in the HR groups was 224 degree days, and in the LR groups was 244 degree days. Hatching commenced at 344 and 347 degree days in the HR and LR groups, respectively, and was complete within 412 and 416 degree days respectively. Overall, selection for stress responsiveness was associated with no significant benefits or costs in reproductive performance. [ABSTRACT FROM AUTHOR]

The present study evaluates if abdominal dis-tension caused by a water-filled stomach in seawater farmed rainbow trout, Oncorhynchus mykiss (Walbaum), and Atlantic salmon, Salmo salar L., could be provoked experimentally by live chilling in sea water (0.5 °C). Fifty rainbow trout and 50 salmon were visually classified, either as normal or suffering from the condition. Prior to chilling, no rainbow trout or salmon suffered from a water-filled stomach. During chilling, 25% of the rainbow trout and 2.5% of the salmon developed water-filled stomach. Affected rainbow trout had significantly higher blood plasma osmolality and significantly lower body weight than normal trout. The frequency of trout with a water-filled stomach increased significantly with increasing chilling time and increasing plasma osmolality. The regression coefficients revealed that the proportion of affected rainbow trout in-creased by 0.82% h-1 of chilling and by 0.46% per unit increase in mosmol L-1. The present study revealed that abdominal distension in seawater farmed rainbow trout was far more severe than in Atlantic salmon and could be provoked experimentally by osmoregulatory stress. This is consistent with the observation that water-filled stomach appear only occasionally in seawater farmed Atlantic salmon. [ABSTRACT FROM AUTHOR]