Chlorpyrifos is a widely applied insecticide that permeates on most waterways and affects aquatic organisms. The growth performances, hematological and histological impacts on Nile tilapia, Oreochromis niloticus following a 60 day of exposure to varying concentrations of chlorpyrifos 20 EC (T₁ 08 µgL⁻¹, T₂ 16 µgL⁻¹, and T₃ 32 µgL⁻¹) were compared to a control T_c 0 µgL⁻¹. The 96-hour LC50 of chlorpyrifos 20 EC was calculated as 46.80 μgL⁻¹. The water quality parameters were recorded regularly. The value of dissolved O₂ and NH₃ stayed rather steady, although temperature varied considerably. It was revealed that as chlorpyrifos levels go up, the percentage of weight gain (WG %), specific growth rates (SGR), and survival rate decreases. The control group T_c had the highest percentages of SGR weight (1.16 ± 0.58) and the T₃ group had the lowest percentages of SGR weight (0.25 ± 0.77). The hematological assessment showed significant differences of hemoglobin concentration, white blood cell counts and red blood cell numbers between chlorpyrifos treatment and control group (P < 0.05). Histological alterations in the liver, gills, and muscle tissues reported to be worse for T₃ as compared to others. There were no statistical differences in GSI, HSI values between control and treatment groups. The chlorpyrifos 20 EC was shown to be highly toxic to O. niloticus at sub-lethal dosages.

Lead (Pb) is one of the toxins responsible for the deterioration of ecological health in aquatic environments. The present study investigated the effects of Pb(NO₃)₂ toxicity on growth, blood cell morphology, and the histopathology of gills, liver, and intestine of juvenile Nile tilapia, Oreochromis niloticus. A 30-day long aquarium trial was conducted by assigning three treatment groups T₁ 5.20 mg L⁻¹, T₂ 10.40 mg L⁻¹, and T₃ 20.80 mg L⁻¹, and a control 0 mg L⁻¹ following the 96 h LC₅₀ of 51.96 mg L⁻¹ from acute toxicity test. Overall growth performance significantly declined in all the Pb(NO₃)₂ treated groups and the highest mortality was recorded in T₃. Behavioural abnormalities were intense in all the treatment groups compared to the control. Hepatosomatic index (HSI) values were reported as higher in treatment groups. Reduced nucleus diameter and nuclei size in erythrocytes were reported for T₂ and T₃ groups. Dose-dependent histological alterations were visible in the gills, liver, and intestine of all the Pb(NO₃)₂ treated groups. The width of the intestinal villi was highly extended in T₃ showing signs of severe histological alterations. In conclusion, Pb toxicity causes a negative effect on growth performance, erythrocyte morphology, and affected the vital organs histomorphology of juvenile O. niloticus.

The purpose of this study is to compare the effects of probiotics, prebiotics, and their synergism against antibiotics on the growth performance and hematology of Nile tilapia (Oreochromis niloticus). The study was designed by using five treatments over 75 days in which T_Con (control), T_Ant (antibiotics: Cotrim vet), T_Pro (commercial probiotics: pond care), T_Pre (prebiotics: spirulina), and T_Syn (synbiotic: probiotic and prebiotic) were used. All the treatments showed significant ( < 0.05) improvements in growth and feed utilization parameters. The highest mean final growth was found in T_Syn (13.79 ± 0.11) and then in T_Pre (13.61 ± 0.02), T_Pro (13.22 ± 0.12), T_Ant (10.04 ± 0.7), and T_Con (8.89 ± 0.19). Weight gain and specific growth rate were significantly ( < 0.05) different between treatments. The food conversion ratio varied significantly ( < 0.05) across treatments and the lowest value was observed in T_Pro (1.13 ± 0.021). The protein efficiency ratio (PER) was significantly ( < 0.05) different between treatments and the highest value was in T_Pro (3.1 ± 0.05). The survival rate was not significantly ( < 0.05) different between treatments. The highest white blood cell (WBC) counts were found in T_Syn (12.63 ± 0.11) followed by T_Pre (12.6 ± 0.2), T_Pro (12.32 ± 0.12), T_Con (12.16 ± 0.105), and T_Ant (11.03 ± 0.46). The values of red blood cells and platelets were not statistically significant ( < 0.05) among the different treatments. However, all treatments showed normal hepatocyte structure in liver tissue histology, and intense hepatic lipid vacuoles in T_Syn indicated improved growth. The higher growth performance and feed utilization values were observed in probiotics, prebiotics, and their synergism units compared to antibiotic treatment. Therefore, probiotics, prebiotics, and their synergism can be used as an alternative to antibiotics in tilapia aquaculture.

The 17α-methyltestosterone is the most common synthetic hormone used in male mono-sex production of Nile tilapia, Oreochromis niloticus. The current research aimed at finding out the most effective dose of 17α-methyltestosterone to produce quality Nile tilapia fry. Soon after absorbing the yolk sac, Nile tilapia fry was fed with a mixture of commercial fish feed and 17α-methyltestosterone for 28 days. Five doses of 17α-methyltestosterone, i.e., 0 mg, 50 mg, 60 mg, 70 mg, and 80 mg per kg feed, were used to treat tilapia that has been reared for additional 90 days to compare sex reversal, development, and survival rates. Both gonad histology and Squash test were performed to expose the sex percentage of O. niloticus accurately. The highest male 94.44% was obtained at 60 mg 17α-MT/kg feed dose followed by 91.67%, 88.89%, 86.11%, and 47.22% at 70, 80, 50, and 0 mg 17α-MT/kg feed dose. The groups treated with 17α-methyltestosterone hormone showed superior growth performance in comparison to the control group. The highest weight (14.62 ± 0.59 g) and length (92.18 ± 3.01 mm) were found at 60 mg dose whereas the lowest weight (8.64 ± 0.38 g) and length (70.17 ± 3.75 mm) were in the control group. The group given 60 mg 17α-MT feed represented the highest survival rate (84.10%) among other hormone-treated groups. The study disclosed that 60 mg 17α-MT/kg feed might be treated as the optimal dose for producing quality mono-sex male tilapia in the commercial hatchery.