Effects of temperature, dissolved oxygen, and their interaction on the growth performance and condition of rainbow trout (Oncorhynchus mykiss)

Interactive effects of water temperature and dietary protein on Nile tilapia: growth, immunity, and physiological health

Optimizing fish performance depends on several factors, with dietary protein levels and rearing temperature playing important roles. In this study, Nile tilapia fingerlings (Oreochromis niloticus) weighing an average of 20.00 ± 1.26 g were divided into nine groups (in three replicates). Each group was subjected to different water temperatures (26 °C, 28 °C, and 30 °C) and received one of three dietary protein levels (20%, 25%, and 30%) for two months. Our findings indicate that higher temperatures, particularly at 30 °C, increased water electrical conductivity and total dissolved salts, especially noticeable in fish fed 25% or 30% crude protein (CP). Lower total ammonia nitrogen levels were observed at 28 °C with 25% CP, 30 °C with 30% CP, and 26 °C with 30% CP. Hepatic growth hormone receptor 1 and insulin-like growth factor 1 expression gradually rose with higher dietary CP percentages in fish at 26 °C but declined in those at 30 °C, albeit remaining higher than in the 28 °C groups with 25% CP. Fish at 28 °C showed the best final body weights and growth performance when fed 20% or 25% CP, with no significant difference between these groups. Hepatic leptin expression did not differ significantly among groups, but hepatic fatty acid binding protein expression notably increased in fish fed 30% CP at both 26 °C and 30 °C compared to those at 28 °C with 25% CP. Within the same temperature group, fish fed 30% CP exhibited higher globulin levels, particularly thriving at 28 °C or 30 °C. Hepatic mucin-like protein expression significantly increased across all groups, especially in fish at 30 °C with 30% CP compared to those at 28 °C with 25% CP. Hepatic lysozyme expression also increased notably in fish at 30 °C with 30% CP. Notable changes in superoxide dismutase, catalase, and glutathione peroxidase expression were observed, with the highest serum superoxide dismutase and catalase activities recorded in fish at 30 °C with 25% CP. Overall, dietary protein levels of 25% and 30%, combined with temperatures of 28 °C and 30 °C, yielded favorable outcomes, particularly favoring 28 °C with 25% protein.

Sediment analysis and water quality assessment in the Pixquiac basin: drinking water supply of Xalapa city (Veracruz, Mexico)

Fluvial sediment analysis and water quality assessment are useful to identify anthropic and natural sources of pollution in rivers. Currently, there is a lack of information about water quality in the Pixquiac basin (Veracruz state, Mexico), and this scarcity of data prevents authorities to take adequate measures to protect water resources. The basin is a crucial territory for Xalapa, the capital city of Veracruz state, as it gets 39% of its drinkable water from it. This research analyzed 10 physicochemical parameters and 12 metal concentrations in various rivers and sources during two seasons. Dissolved metals presented average concentrations (µg/L): Al (456.25) > Fe (199.4) > Mn (16.86) > Ba (13.8) > Zn (7.6) > Cu (1.03) > Pb (0.27) > As (0.12) > Ni (0.118) (Cd, Cr and Hg undetectable). Metals in sediment recorded average concentrations (ppm): Fe (38575) > Al (38425) > Mn (460) > Ba (206.2) > Zn (65.1) > Cr (29.8) > Ni (20.9) > Cu (16.4) > Pb (4.8) > As (2.1) (Cd and Hg undetectable). During the rainy season, Water Quality Index (WAWQI) classified stations P17 and P18's water as "unsuitable for drinking" with values of 110.4 and 117.6. Enrichment factor (EF) recorded a "moderate enrichment" of Pb in sediment in P24. Pollution was mainly explained by wastewater discharges in rivers but also because of erosion and rainfall events. Statistical analysis presented strong relationships between trace and major metals which could explain a common natural origin for metals in water and sediment: rock lixiviation.

Practical application of bicultural stocking and its effects on fish growth, blood biochemistry, and solid waste elimination in recirculating aquaculture system

Traditional monoculture systems often face challenges related to solid waste production and nutrient use. This study addresses these concerns by investigating the impact of bicultural farming of burbot (Lota lota) and rainbow trout (Oncorhynchus mykiss) in a recirculating aquaculture system (RAS) and the subsequent alteration of production of solid waste, growth and physiological status. The rationale behind incorporating burbot lies in its potential as a supplementary species to improve overall system efficiency and sustainability. The experimental groups in triplicate represented the different ratios of rainbow trout (T) and burbot (B) in the stock: T70/B30, T85/B15 and T100/B0. Burbot, although not assessed in monoculture due to its limited commercial significance, was incorporated into the study as a supplementary species, expected to enhance the nutrient utilisation through its bottom-feeding behaviour and anticipated consumption of solid waste produced by trout. After 77 days of culture, the survival rates of trout remained consistent across experimental groups, averaging over 99%, while burbot exhibited comparable survival rates despite lower cumulative survival, averaging 88%. Feed conversion ratios showed no significant differences between the groups, indicating consistent feed utilisation. A significantly higher specific growth rate (SGR) in trout was observed in group T70/B30. The SGR values of burbot were marginally low and without significant differences between groups. Among biochemical markers of blood plasma, phosphorus concentrations were significantly higher in group T70/B30 for both trout and burbot, suggesting better access to the feed for both species. Elevated antioxidant activity and evidence of oxidative stress were found for both species in intestinal tissue. The presence of burbot in stock significantly affected the production of suspended solids per gram of applied feed. Therefore, group T100/B0 demonstrated the highest solid production at multiple time points, suggesting a relationship between burbot presence and the production of suspended solids. Starting at the 9-week, the trout monoculture group exhibited significantly higher phosphorus levels in sediments compared to group T70/B30, emphasising the role of burbot in shaping sediment nutrient dynamics in RAS, such as supplementary cleaning fish. After 11 weeks, group T100/B0 displayed significantly higher values of produced suspended solids and their composition: DM, organic DM, and phosphorus content per gram of feed applied. These results provide evidence of the influence of burbot on suspended solids production and characteristics. In conclusion, this study indicates the positive effects of burbot presence on solid production and sediment nutrient composition.

H2O2-Induced Oxidative Stress Responses in Eriocheir sinensis: Antioxidant Defense and Immune Gene Expression Dynamics

Eriocheir sinensis, a key species in China's freshwater aquaculture, is threatened by various diseases, which were verified to be closely associated with oxidative stress. This study aimed to investigate the response of E. sinensis to hydrogen peroxide (H2O2)-induced oxidative stress to understand the biological processes behind these diseases. Crabs were exposed to different concentrations of H2O2 and their antioxidant enzyme activities and gene expressions for defense and immunity were measured. Results showed that activities of antioxidant enzymes-specificallysuperoxide dismutase (SOD), catalase (CAT), total antioxidant capacity(T-AOC), glutathione (GSH), and glutathione peroxidase (GSH-Px)-varied with exposure concentration and duration, initially increasing then decreasing. Notably, SOD, GSH-Px, and T-AOC activities dropped below control levels at 96 h. Concurrently, oxidative damage markers, including malondialdehyde (MDA), H2O2, and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, increased with exposure duration. The mRNA expression of SOD, CAT, and GSH-Px also showed an initial increase followed by a decrease, peaking at 72 h. The upregulation of phenoloxidaseloxidase (proPO) and peroxinectin (PX) was also detected, but proPO was suppressed under high levels of H2O2. Heat shock protein 70 (HSP70) expression gradually increased with higher H2O2 concentrations, whereas induced nitrogen monoxide synthase (iNOS) was upregulated but decreased at 96 h. These findings emphasize H2O2's significant impact on the crab's oxidative and immune responses, highlighting the importance of understanding cellular stress responses for disease prevention and therapy development.

Effect of climate change on fillet quality and shelf-life of Oncorhynchus mykiss under controlled conditions

BACKGROUND

Temperature, which affects numerous physiological processes, has been described as the 'main ecological factor' for fish. The aim of this modeling study is to explore the impact of climate-induced temperature changes on fish fillet quality and shelf life.

RESULTS

Temperature stress in rainbow trout affected ash and moisture, and inhibited myofibril fragmentation in the fillets. However, with the increase in temperature, there was a decrease in the total amount of saturated fatty acids (∑SFA) and there were significant increases in the total amount of omega 3 (∑n3) and 22:6n-3 (DHA). It was determined that temperature increase had a negative effect on color, texture, water-holding capacity, water activity, pH, lactic acid, and glycogen levels in fillets, and it had a positive effect by delaying microbial spoilage, especially in cold storage.

CONCLUSION

This study suggest that the effects of climate change on product quality and shelf life in fish requires further research. It highlights knowledge gaps to guide future research in this emerging field. © 2023 Society of Chemical Industry.

Effect of temperature on growth, survival, and chronic stress responses of Arctic Grayling juveniles

Arctic Grayling Thymallus arcticus are Holarctically distributed, with a single native population in the conterminous United States occurring in the Big Hole River, Montana, where water temperatures can fluctuate throughout the year from 8 to 18 °C. A gradual increase in mean water temperature has been reported in this river over the past 20 years due to riparian habitat changes and climate change effects. We hypothesized that exposing Arctic Grayling to higher temperatures would result in lower survival, decreased growth, and increased stress responses. Over a 144-day trial, Arctic Grayling juveniles were subjected to water temperatures ranging from 8-26 °C to measure the effects on growth, survival, gene expression and antioxidant enzyme activity. Fish growth increased with increasing water temperature up to 18 °C, beyond which survival was reduced. Fish did not survive at temperatures above 22 °C. In response to temperatures above 16 °C, a 3-fold and 1.5-fold increase in gene expression was observed for superoxide dismutase (SOD) and glutathione peroxidase (GPx), respectively, but no changes were seen in the ratio of Heat Shock Protein 70 (HSP70) and heat shock protein 90 (HSP90) expression. Enzyme activities of SOD and GPx also rose at temperatures above 16 °C, indicating heightened oxidative stress. Catalase (CAT) gene expression and enzyme activity decreased with rising temperatures, suggesting a preference for the GPx pathway, as GPx could also be providing help with lipid peroxidation. An increase of Thiobarbituric acid reactive substances (TBARS) was also recorded, which corresponded with rising temperatures. Our findings thus underscore the vulnerability of Arctic Grayling to minor changes in water temperature. Further increases in mean water temperature could significantly compromise survival of Arctic Grayling in the Big Hole River.

Effect of dietary koumine on the immune and antioxidant status of carp (Cyprinus carpio) after Aeromonas hydrophila infection

Koumine (KM) has anxiolytic, anti-inflammatory and growth-promoting effects in pigs and sheep. Based on the growth-promoting and immunological effects of koumine, the present study was conducted on Cyprinus carpio (C. carpio) with four KM concentrations: 0 mg/kg, 0.2 mg/kg, 2 mg/kg, and 20 mg/kg for 10 weeks, followed by a 1-week Aeromonas hydrophila (A. hydrophila) infection experiment. The effect of KM on the immunity of A. hydrophila infected carp was analyzed by histopathology, biochemical assay, and qRT-PCR to assess the feasibility of KM in aquaculture. The results showed that the presence of KM alleviated pathogen damage to carp tissues. At 2 mg/kg and 20 mg/kg concentrations of KM successively and significantly elevated (p < 0.05) the SOD activities in the intestinal tract, hepatopancreas and kidney of carp. The expression levels of hepatopancreatic antioxidant genes Nrf2 and IGF-1 were significantly up-regulated in the same group (p < 0.05), while the expression levels of immune genes IL-8 and IL-10 were down-regulated. In summary, KM at concentrations of 2 mg/kg and 20 mg/kg could regulate the expression of antioxidant and immune genes in various tissues in an orderly and rapid manner, and significantly improve the antioxidant and immune abilities of carp, which is conducive to the improvement of the resilience of carp.

Effects of water temperature on growth performance, digestive enzymes activities, and serum indices of juvenile Coreius guichenoti

This study was conducted to determine the optimal temperature for Juvenile Coreius guichenoti, which is critically endangered in China. Test fish with an initial body weight range of 17.60-18.78 g were reared in 5 independent recirculating aquaculture systems (RAS) with three tanks (50 fish/tank) for 8 weeks. The water temperature of the RAS was set at 14 °C, 18 °C, 22 °C, 26 °C, and 30 °C, respectively. At conclusion of the feeding trial, the effects of water temperature on C. guichenoti were analyzed based on survival, growth performance, digestive enzymes activities, and antioxidant capacity. The results showed that the fish survived in all temperature groups. The fish in the groups (26 °C and 30 °C) had higher values of body length, body weight, specific growth rate, weight gain rate, and daily gain than those in the group (22 °C). The lowest values of growth performance were observed in the groups (14 °C and 18 °C) among the 5 groups. The lowest values of feed conversion ratio (FCR) were observed in the group (26 °C). Regression analysis identified the minimum FCR at 26.55 °C. The feeding rates (FR) were increased gradually with the increase of temperature. Regression analysis identified the maximum FR at 28.33 °C. The activities of protease and lipase in the gut were higher than those in the liver, while amylase activity was lower in the gut than that in the liver. There were no significant differences in activities of protease and lipase among different parts of the intestinal tract at the temperatures range from 18 to 26 °C. When the temperature was out the optimal range, C. guichenoti would be under chronic stress, resulting in decreased lysozyme activity and cortisol concentration. Inconclusion, the optimal temperature for juvenile C. guichenoti is 26.55-28.33 °C based on the maximal growth performance and feed utilization.

Alkali exposure induces autophagy through activation of the MAPKpathway by ROS and inhibition of mTOR in Eriocheir sinensis

Saline-alkali water is widely distributed around the world, and salinization of water ecosystems has occurred in some areas of the world, comprising approximately one-third of the total land area, which has drawn much attention to the conservation of water ecosystems and aquatic animals. However, due to the complex composition of saline-alkaline water, many aquatic animals are unable to survive, which greatly limits the development and utilization of saline-alkaline waters. Carbonate alkalinity is an important stress factor for aquatic animals in saline-alkaline water. Exposure to highly alkaline carbonate can induce oxidative stress. For this study, we used Eriocheir sinensis as a model organism to evaluate the effects of alkaline stress on oxidative stress and autophagy. The trial was divided into five alkali level treatment groups (control, 4.375 mmol/L, 8.75 mmol/L, 17.5 mmol/L, and 35 mmol/L, respectively), and liver tissues were assessed by antioxidant enzyme kits, real-time quantitative PCR assays and ultrastructural observations at 3 time points (24 h, 48 h, 96 h). Compared with the control group, the activities of antioxidant enzymes (superoxide dismutase (SOD), glutathione reductase (GSH), glutathione peroxidase (GSH-PX) and total antioxidant capacity (T-AOC)) in the alkali stress group increased and then decreased with increasing time, while the content of malondialdehyde (MDA) increased. At the molecular level, the expression of MAPK pathway-related genes (P38, MAPK, JNK) in the alkaline stress group showed a dose-dependent increase at 48 and 96 h and was significantly higher than that in the control group. The expression of autophagy-related genes (ATG5, ATG12, ATG7 and GABARAP) increased dose-dependently at 24, 48, and 96 h and was significantly higher than that in the control group. In contrast, mTOR expression was always in a suppressed state. These results suggest that alkaline stress induces activation of the MAPK pathway via ROS and inhibits mTOR expression, thereby inducing autophagy in the liver tissue of Eriocheir sinensis. This study investigated the stress mechanism of carbonate on Eriocheir sinensis and provided a theoretical basis for the continued exploitation of saline-alkaline water aquaculture.

Quercetin Application for Common Carp (Cyprinus carpio): I. Effects on Growth Performance, Humoral Immunity, Antioxidant Status, Immune-Related Genes, and Resistance against Heat Stress

This study was done to evaluate the effect of different quercetin levels on growth performance, immune responses, antioxidant status, serum biochemical factors, and high-temperature stress responses in common carp (Cyprinus carpio). A total number of 216 common carp with an average weight of 27.21 ± 53 g were divided into 12 tanks (four treatments × three replications) and fed 0 mg/kg quercetin (T0), 200 mg/kg quercetin (T1), 400 mg/kg quercetin (T2), and 600 mg/kg quercetin (T3) for 60 days. There were significant differences in growth performance, and the highest final body weight (FBW), weight gain (WG), specific growth rate (SGR), and feed intake (FI) were observed in T2 and T3 (P < 0.05). Different quercetin levels significantly increased complement pathway activity (ACH50) and lysozyme activity both before and after heat stress (P < 0.05). Catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) were significantly increased in fish exposed to heat stress, but fish fed with a supplemented diet with quercetin showed the lowest levels both before and after heat stress (P < 0.05). Superoxide dismutase (SOD) levels were significantly enhanced in fish fed diets supplemented with quercetin in both phases (P < 0.05). Different quercetin levels led to a significant decrease in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) before and after the challenging test (P < 0.05). Glucose and cortisol levels were significantly higher in the control group compared to the other treatments in both phases (P < 0.05). The expression of glutathione peroxidase (GPx) and lysozyme was markedly upregulated in fish fed with quercetin-supplemented diets (P < 0.05). No marked effects were observed for growth hormone (GR) and interleukin-8 (IL8) (P > 0.05). In conclusion, dietary quercetin supplementations (400-600 mg/kg quercetin) improved growth performance, immunity, and antioxidant status and increased tolerance to heat stress.

Influences of oxygen and temperature interaction on the antibacterial activity, antioxidant activity, serum biochemical indices, blood indices and growth performance of crucian carp

The well-being of fish used in aquaculture is of great interest. Oxygen and temperature are the main factors affecting the welfare of the crucian carp (carassius); however, there are few studies on the combined effects of these on the species. Therefore, this study investigated the impact of different temperatures (18 °C, 24 °C, 30 °C) and oxygen concentrations (2.1 mgL-1, 5.4 mgL-1, 9.3 mgL-1) on serum antibacterial activity, antioxidant activity, hematological parameters and growth performance of the crucian carp. The results showed that there were greater antibacterial properties under conditions of hypoxia at 18 °C (L18) and hyperoxia at 24 °C (H24). The activities of catalase, glutathione peroxidase and total superoxide dismutase were the highest at 24 °C under hypoxia and hyperoxia. In addition, the contents of glucose and total protein first increased and then decreased with the change of temperature; triglycerides were the lowest at 30 °C. The blood parameters of the carp were within a normal range at 24 °C; however, the growth rate was at its lowest under hypoxia treatment at 30 °C (L30). This study showed that high temperature impairs the antibacterial ability, antioxidant capacity and growth performance of the crucian carp, and high oxygen levels can alleviate these adverse reactions. This research provides a theoretical basis for subsequent aquaculture studies.

Transcriptome sequencing reveals the effect of selenium nanoparticles on primary hepatocytes of rainbow trout

Heat stress is one of the important threats in rainbow trout culture, and selenium nanoparticles (SeNPs) have an important role in combating heat stress and enhancing immunity. In this study, to enable rainbow trout to survive at higher temperatures, we added 5 µg/mL SeNPs to hepatocytes to study the resistance effect and immune effect of SeNPs against heat stress, thus enabling rainbow trout to adapt to summer temperatures (Average 26 °C) in Lanzhou, Gansu Province, China. Therefore, we investigated the transcriptome expression profile of hepatocytes spiked with SeNPs when exposed to heat stress. A total of 234 differentially expressed genes (DEGs) were firmly established in SeNPs-added group when exposed to heat stress compared to non-SeNPs-added group. Of these DEGs, 156 were up-regulated and 78 were down-regulated. These DEGs were grouped into different Gene Ontology (GO) functional terms and enriched in 75 significantly different Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, of which approximately-one-third (19) were associated with immunity. STRING was used to identify 39 key immune DEGs belonging to 5 immune pathways (C-type lectin receptor signaling pathway, FoxO signaling pathway, Toll-like receptor signaling pathway, RIG-I-like receptor signaling pathway, and Rachidonic acid metabolism). These pathways interact extensively and formed a complex network to regulate heat stress. These results provided an important basis for future elucidation of the role of SeNPs in heat stress resistance and immune enhancement in rainbow trout.

Deep-sea cage culture altered microbial community composition in the sediments of the Yellow Sea Cold Water Mass

Environmental impacts of the first submersible salmonid culture cage, which was launched in the deep-sea of the Yellow Sea Cold Water Mass, were investigated. The temporal and spatial variations of several physicochemical parameters were observed in both the bottom and sediment pore water. Aquaculture activities decreased bacterial richness in the sediment. The dominant phyla Proteobacteria, Desulfobacterota and Acidobacteriota, accounted for 30.42 % of the total bacteria community. Principal component analysis indicated that the bacterial composition in December was different from that in the other three months, and the aquaculture activity affected the distribution of the sediment microbial community in June, August and April. Planctomycetes was selected as biomarkers in the aquaculture area by linear discriminant analysis effect size. Redundancy analysis showed that the biomarkers were positively correlated with temperature and the concentration of nitrite in June, and negatively correlated with the dissolved oxygen in August and April.

Concurrent changes in thermal tolerance thresholds and cellular heat stress response reveals novel molecular signatures and markers of high temperature acclimation in rainbow trout

The objective of this study was to better understand the molecular mechanisms which regulate acclimatory responses and thermal safety margins of rainbow trout (Oncorhynchus mykiss) at temperatures above physiological optimum. For this, we investigated the time course of changes in critical thermal tolerance thresholds and associated hepatic and renal transcript abundance of molecular markers related to cellular stress response, during high temperature acclimation. The experimental fish were initially acclimated to 17 °C and later exposed to a gradually raised elevated temperature regime (22 °C) for a period of 30 days. CT_max, CT_min and mRNA expression of candidate markers were examined before the thermal challenge (T₀) and over the time-course (days) of high temperature exposure (T₁, T₃, T₇, T₁₅ and T₃₀). With respect to organismal response, CT_max was significantly elevated at T₃, but the degree of gain in heat tolerance was not persistent. Contrarily, we observed a gradual loss in cold tolerance with highest CT_min estimate at T₃₀. Based on the time-course of mRNA expression, the studied markers could be categorized into those which were persistently elevated (hsp70a, hsp70b, hspa5, hsp90a, hsp90b, stip1 and serpinh1 in kidney and hsp90b in liver); those which concurred with changes in CT_min (hspbp1, hsp90b, stip1, gr1, hif1a, hyou1, tnfa and tlr5 in kidney); and those which concurred with changes in CT_max (hsp90a, serpinh1, tlr5 and lmo2 in liver). Apparently, transcriptional changes in kidney and liver reflected CT_min and CT_max trend, respectively. Expression profile of stip1 and tlr5 suggest that they are potential novel markers which could reflect thermal limits in rainbow trout. Hepatic metabolic markers were either initially elevated (alt, glud, g6pase1) or down-regulated at different time-points (ast2, gls1, fas, cpt1b, mtor), linked to gluconeogenesis and metabolic depression, respectively. Whereas, growth-axis markers showed no significant differences. Overall, this time-course analysis has revealed potential associations in organismal and tissue-specific cellular response to high temperature acclimation in a thermally sensitive coldwater ectotherm.