This work was designed to evaluate the influence of mercury chloride on some of biochemical and immunological biomarkers in common cap, Cyprinus carpio. Around of 120 fish were randomly allocated into four groups (30 fish per group) in triplicates as follows; first group act as control group provided with water only without adding HgCl2;  G1, G2 and G3 were exposed to waterborne  HgCl2 at levels of  0.01, 0.05 and 0.1 mg l-1 respectively. After one month exposure to HgCl2, there were significantly decreased (P<0.05) in lymphocyte transformation index and in phagocytic and lysozyme activities. Besides, biochemically, Albumin and globulin content exhibited significantly declined (P<0.05) particularly at higher dose of HgCl2. In contrast, blood glucose value and urea showed significantly increased (P<0.05) especially in G3. On the other hand, variable changes were observed in total count of leucocytes included lymphopenia and neutrophilia in G1 and G2 compared to control.  In conclusion, this investigation indicated that mercury chloride has immune suppressive effects and is extremely toxic to common carp.

This study was aimed to investigate the lead and cadmium in water and in fish samples collected from three sites of Gharraf River at Thi Qar from September 2020 until April 2021. Results showed that (Pb) in river water ranged 0.156 - 4.306µg/l and the (Cd) 0.074 - 0.523 µg/l which recorded a significant differences among all sites as well as among all seasons. In addition the concentrations of Pb in some tissues  of  Cyprinus carpio ranged 0.069 - 4.98µg/g in muscles and kidney respectively, while Cd  ranged  0.038 - 1.46 µg/g in muscles and kidney respectively. The study also showed a significant differences in Pb concentrations in fish tissues among all sites during seasons and recorded a significant differences in the summer compared with other season for Pb and Cd. A significant difference was also found in Pb and Cd concentrations between cages fish and the wild fishes for all seasons. The study proved that the water of the Al-Gharraf River is of low toxicity and less than the Iraqi and international standards, and the accumulation of Pb and Cd in the muscles of fish was less than the limits of the Federal Agency for Environmental Protection and the World Health Organization.

The objective of the current study is to determine the effects of lead acetate (Pb (CH 3 COO 3) 2) on haematological parameters, behavioural changes and body weight in the cyprinid fish Bunni Mesopotamichthys sharpeyi. For this purpose, a total of 120 fish were distributed randomly among four treatments in addition to a control group. Treatments included exposing to lead acetate at 0.2mg l-1 and 0.4 mg l-1 with replacement of aquarium water every two days and adding lead acetate continuously or for the first time only. After 15, 30 and 60 days blood parameters were measured. Body weight was measured at beginning and end of experimental period. Behavioural responses were also recorded during the course of experiment. Results revealed significant decrease in red and white blood cells count, hemoglobin concentration, packed cell volume compared to control group. Results showed a presence of improvement of clinical and blood picture in treatments with changing water aquarium continuously. Abnormal behaviour was observed in all treatments but the severity of signs increased with exposing to high concentration of lead acetate. Growth rate showed significant decrease in all treatments in comparison with control group. In conclusion, exposure to lead acetate could cause several changes in blood profiles, but changing of water aquarium without adding lead acetate led to improvement of health status of fish.

     The present study was carried out during the period from November 2015 to April 2016 to determine the concentration of lead in Tigris River. A total of 75 fish of Hamri Carrasobarbus luteus and 82 specimen of common carp Cyprinus carpio were sampled at three different stations. Atomic absorption spectrometry is a technique for measuring quantities of Lead present in water and fish. The results showed that the mean concentration of lead in water more than in fish organs. Statistical analysis showed no significant differences in lead concentration between all stations. In C. luteus and C. carpio showed no significant differences in gills, muscles, liver and kidney between different length groups for each station. Length group 21- 30 cm at station 2 showed increasing differences compared with the same length group at station 1, Also C. carpio of Length group 31-40 cm at station 2 showed significantly  increasing (P≤0.05) compared with the same length group at station 1. The highest concentration of lead was recorded in studied organs of C. luteus at station1as the following sequence: Gills > kidney > liver > muscles, while station 2:  kidney > gills > liver > muscles, station 3 characterized as following sequence: Kidney > liver > gills > muscles. The highest concentration of lead was recorded in studied organs of C.carpio at station1as the following sequence: Gills > liver > muscles > kidney, while station 2:  Gills > kidney > liver > muscles, station 3 characterized looks like a sequence of station 1 as following: Gills > liver > muscles > kidney. In conclusion, the result of the present study approved the presence of lead in the water of Tigris River and fish living inside it. In addition, the mean concentration of lead in water was more than in fish organs. The results also reported that lead concentration was higher than the allowable WHO concentration.

In present study, we assessed the role of kaolin [(Al2Si2O5(OH)4), an inert clay], for treatment of  common carp, Cyprinus carpio experimentally infected with  Pesudomonas aeruginosa. Fish were experimentally challenged with P. aeruginosa (LD50= 2±0.2×109 CFU/ml), in untreated water or water treated with addition of kaolin at levels of 4, 6 and 8g/l (G1, G2 and G3 respectively). Over the 5‐day course of kaolin treatment led to significantly (P ≤ 0.05) improved of survival (100%) in treated groups (G2 and G3) as compared to untreated fish (infected group; 75% survival). Considerable changes were observed in blood parameters, leucocyte count recorded significant increase (P≤0.05) in G2 and G3 relative to C- and C+ groups. Erythrocyte count, Hb content and HT(%) reported significant decrease (P≤0.05) in all treated groups (G1, G2 and G3) related to C- group. Globulin level registered significantly increased (P≤0.05) in G2 and G3 than C+ group.  The current study strongly recommends that treatment of common carp infected with kaolin at 6 and 8g/l improves survival, hematological and biochemical profile, against P. aeruginosa. Future complete molecular studies are required before application of kaolin as a treatment in aquaculture.