Boran Karataş

In this study, a 42-day feeding trial was conducted to evaluate the effects of Althaea officinalis extract on growth performance, antioxidant defense, stress-associated, and immune-related gene expression in rainbow trout (Oncorhynchus mykiss) with an initial average body weight of 2.48 ± 0.01 g. Three experimental diets were formulated: a basal control diet (C) and two diets supplemented with different levels of A. officinalis extract (AO1, 1 g kg-1 and AO2, 2 g kg-1). Growth indices showed significant improvements in both A. officinalis supplemented groups compared to the C group (P < 0.05). Gene expression levels of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) were significantly elevated in the supplemented groups (P < 0.05). Additionally, the expression of stress, and immune-related genes, including interleukin-1β (IL-1β), tumour necrosis factor-alpha (TNF-α), interleukin-8 (IL-8), and heat shock protein 70 (HSP-70), was also significantly influenced by dietary inclusion of A. officinalis extract (P < 0.05). Overall, these findings provide experimental evidence that dietary inclusion of A. officinalis extract enhances antioxidant capacity, modulates stress and immune-related gene expression, and promotes healthy growth in rainbow trout. These beneficial effects may be attributed to the presence of flavonoids and phenolic compounds in A. officinalis, which are known for their antioxidant and immunomodulatory properties.

Dissolved oxygen (DO) is a vital parameter in intensive rainbow trout aquaculture, directly influencing fish growth, health, and survival. As such, accurate monitoring and prediction of DO levels are crucial for ensuring sustainable and efficient aquaculture practices. This study assessed and compared the predictive performance of four machine learning algorithms Multivariate Adaptive Regression Splines (MARS), Random Forest (RF), Extreme Gradient Boosting (XGBoost), and Averaged Neural Networks (avNNet) in estimating DO concentrations based on a range of water quality parameters. A total of 120 samples were collected from 12 rainbow trout farms across Türkiye. The input variables included suspended solids, electrical conductivity, turbidity, nitrate, nitrite, ammonia, ammonium, orthophosphate, pH, water temperature, and total phosphorus. DO levels ranged between 8 and 15 mg/L. Model performance was evaluated using Mean Absolute Error (MAE), Root Mean Square Error (RMSE), Mean Absolute Percent Error (MAPE), and the coefficient of determination (R²). All models demonstrated strong predictive accuracy, with XGBoost achieving the best overall performance (MAE: 0.44, RMSE: 0.58, MAPE: 0.04, R²: 0.78), followed by RF, avNNet, and MARS. These findings highlight XGBoost as a robust predictor of dissolved oxygen levels in aquaculture systems, which may contribute to improving water quality management and increasing productivity in rainbow trout aquaculture.

This study aimed to investigate the genetic diversity and structure of rainbow trout (Oncorhynchus mykiss) cultured populations in different provinces of Türkiye, based on the cytochrome b (cyt-b) gene region of mitochondrial DNA (mtDNA). Tissue samples were collected from a total of 98 fish (seven fish per province) across 14 provinces, followed by DNA isolation. The mtDNA cyt-b gene region (754 bp) was amplified using PCR. Genetic diversity indices, genetic structure, and phylogenetic analyses were calculated from the cyt-b gene sequence data. The average nucleotide frequencies of the four nucleotides cytosine (C), thymine (T), adenine (A), and guanine (G) were found to be 26.2%, 24.9%, 26.2%, and 22.8%, respectively, with a higher A + T content (51%) compared to G + C content (49%). A total of 645 polymorphic nucleotides were identified across the 14 populations, and 50 distinct haplotypes were defined. Haplotypic diversity ranged from 0.91 to 0.48, while nucleotide diversity (π) varied between 0.26 and 0.00. The highest genetic diversity was observed in the Tokat and Van populations, whereas the lowest was recorded in the Elazığ and Kahramanmaraş populations. AMOVA analyses revealed that 71.1% of the genetic diversity was found between populations, while 28.9% was found within populations. Pairwise FST values ranged from 0.38 to 0.99, with an average FST of 0.71. Phylogenetic analyses indicated that the populations clustered into two main groups, with further sub-groupings within these clusters. Notably, the Kahramanmaraş and Elazığ populations were found to be significantly differentiated from other populations. In conclusion, despite rainbow trout not being a native species in Türkiye, the findings of this study indicate that the genetic diversity of the populations is at a good level. However, in order to preserve the genetic diversity of cultured rainbow trout populations and to increase effective population size, it is recommended that breeders engage in fry exchanges and import new rainbow trout specimens to enhance genetic diversity.

In this study, a 60‐day trial was conducted to determine the effects of curry plant (Helichrysum italicum) extract in the diet of rainbow trout (Oncorhynchus mykiss) with an initial average live weight of 15.84 ± 0.05 g on growth performance and gene expressions associated with digestion, antioxidant capacity, and immune response. Four experimental diets were formulated as a basal diet (Control; C) and diets supplemented with varying levels of curry plant extract (CP05; 0.5 g kg⁻¹, CP1; 1 g kg⁻¹, and CP2; 2 g kg⁻¹). Growth indices showed significant increases in all curry plant extract groups compared to the C group (p < 0.05). Similarly, higher levels of trypsin, lipase, and amylase expressions were observed in the curry plant extract groups compared to the C group (p < 0.05). The superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) gene expression levels were elevated in the CP extract groups (p < 0.05). The expression levels of interleukin‐1β (IL‐1β), tumor necrosis factor (TNF‐α), and interleukin‐8 (IL‐8) were also influenced by the incorporation of CP extract into the diet, showing significant changes (p < 0.05). In conclusion, this study experimentally demonstrates that supplementing the diet of rainbow trout with CP extract can positively influence healthy growth parameters.

His study investigates the effects of dietary gallic acid (GA) supplementation on growth performance and the expression of genes linked to antioxidant, stress, and immune functions in rainbow trout (Oncorhynchus mykiss). Fish with an average body weight of 2.84 ± 0.25 g were fed diets containing 0 mg/kg (control), 300 mg/kg (G300), 450 mg/kg (G450), and 600 mg/kg (G600) of GA over 60 days. The results revealed significant improvements in growth indices, including weight gain, specific growth rate, and feed conversion ratio, in GA-supplemented groups compared to the control (P<0.05). At the molecular level, GA supplementation significantly upregulated the expression of antioxidant-related genes (SOD, CAT, GPX), stress-related genes (HSP70), and immune-related genes (TNF-α, IL-1β). The G300 group consistently exhibited the most pronounced transcriptional responses, while higher doses (G450 and G600) showed diminished or inconsistent effects. These findings suggest that a dietary inclusion of 300 mg/kg GA optimally enhances fish health and productivity by modulating key molecular pathways. This dosage is recommended as an effective feed additive for improving the performance and resilience of rainbow trout in aquaculture.

In this study, the effects of Schizochytrium sp. supplementation (SCH) to feed on growth and skin coloration in electric yellow cichlid (Labidochromis caeruleus) were investigated. Fish (1.93 ± 0.23 g initial weight) were fed with commercial fish feed as the control group (C) and commercial fish feed supplemented with 0.5% (SCH05) and 1% (SCH1) SCH for 60 days. The SCH05 and SCH1 groups displayed the highest final weight (FW), weight gain (WG), and specific growth rate (SGR) values, with similarly favorable feed conversion ratio (FCR) levels compared to the C group (p<0.05). The SCH1 group exhibited statistically significant differences from the C and SCH05 groups concerning lightness (L*) and hue values (p<0.05). The redness (a*) values in the SCH05 and SCH1 groups showed a statistically significant difference compared to the C group (p<0.05). However, there were no statistically significant differences in the yellowness (b*) and Ch values among all groups. To conclude, the inclusion of SCH microalga as a dietary supplement markedly promoted growth performance and facilitated the attainment of marketable size in electric yellow cichlids. Additionally, although the enhancement in skin coloration resulting from the addition of 0.5% SCH to the feed did not reach a significant difference, it hints at a promising advantage that could enhance the aesthetic allure and market value of the fish.

This study aimed to assess the combined effects of Cyanus depressus and Schizochytrium sp. extracts on growth indices and the expression of genes linked to antioxidant activity and immunity in carp (Cyprinus carpio). Fish, averaging 3.71 ± 0.16 g in weight, were assigned to three dietary groups over a 60-day period: a control group (0 g/kg extract) and two test groups receiving extract mixtures at 0.5 g/kg (CS05) and 1 g/kg (CS1). The supplemented groups, particularly those at 0.5 and 1 g/kg, showed significant increases in final body weight, weight gain, and specific growth rate. The highest superoxide dismutase (SOD) and catalase (CAT) gene expression levels were seen in fish on the 0.5 g/kg CS-supplemented diet, and CS-fed groups displayed the greatest expression of the immune-related gene interleukin-1 beta (IL-1β) relative to the control. Collectively, these findings indicate that Cyanus depressus and Schizochytrium sp. extracts, especially at a dosage of 0.5 g/kg, have promising potential as dietary supplements for enhancing the physiological health and growth of carp.

The negative effects of global warming also directly affect aquatic populations. Consequences such as evaporation due to chronic temperature increase, increase in salinity, and increase in stock density per unit volume are potential stress factors. While creating the trial design, an attempt was made to simulate the effects of global warming, especially on species living in salty and brackish water biotopes. In this study, changes in the gills of rainbow trout (Oncorhynchus mykiss) acclimated to 0, 20, and 38 ‰ of saline in the laboratory were examined histologically and immunohistochemically and blood serum osmolarity. In addition, the water temperature was changed, and experiments were carried out at 16, 19, and 22 °C for each salinity group in parallel with the increase in salinity. However, to simulate the decrease in water volume and intensive stocking due to the potential impact of climate change, the study was carried out using 15 fishes in low-volume aquariums (45 L). Tap water that had been kept for at least 3 days was used in the aquariums. To protect the water quality, independent aquariums with sponge filters were used, and since the aim was to keep dissolved oxygen low, no ventilation system other than the sponge filter was used. In order to minimize the deterioration in water quality during the trial, a 15% water change was performed by performing a bottom flush every 4 days and water of the same temperature and salinity was added as much as the reduced volume. In addition, since increasing stock density due to temperature increase and water decrease will cause the amount of dissolved oxygen to decrease, pure oxygen was not entered into any tank throughout the experiment, and the concentration was requested to be at a low level (7 ± 0.13 mg/L) in all groups. The trials were terminated at the end of the 71st day. Increased serum osmolarity values were observed due to the increase in salinity, and the highest serum osmolarity value was measured at 644 mOsm/kg in the 38 ‰ salinity group. Differences between the groups were found to be statistically significant (p < 0.05). It was observed that the number of cells containing Na⁺/K⁺-ATPase increased depending on salinity. Also, the number of chloride cells reached the maximum level in the 38 ‰ salinity group. Due to increasing salt levels, an increase in mucus cells, limited onset hyperplasia, aneurysm, lamellar separation, and necrosis were observed in the gill tissue.