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This paper presents  the  levels  of total  mercury  (T-Hg)  in  dorsal  muscle,  liver  and  spleen of pike  (Esox lucius) from  Anzali  Lagoon  in Iran.  Sampling were  carried  out from  July  2004 to July 2005. In addition 78 samples were collected. T-Hg concentration  were  calculated  in relation to biometric factors. T-Hg was measured by the LECO AMA 254 Advanced Mercury Analyzer (USA) according to ASTM standard NoD-6722. Each sample was analyzed 3 times. Accuracy of T-Hg analysis was checked by running three samples of Standard Reference Materials; SRM 1633b, SRM 2711 and SRM 2709. Detection limit was  0.001mg/kg  in  dry weight. The minimum and maximum  concentration  ofT-Hg  in  dorsal  muscle  was  0.2ppm  in one year and 1.2ppm in five year class. The mean T-Hg significantly  increased  wit  age increased (P<0.05). The T-Hg mean concentration.  In 1 and 2 year classes was 0.171ppm. Accamulation pattern ofHg was significantly as well as muscle>liver>spleen. T-Hg content in females was higher than males (P<0.05). Acceptable monthly intake without carcinogenic effects due to mercury  for women, men, juveniles and children was 270,  320,  125 and  59g per  month.  Consumption  of pike above 35cm. length should be avoided.

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Mercury, zinc and selenium concentrations were analyzed in the muscle and liver of 25 Whitecheek Shark (Carcharhinus dussumieri) from the coast of Bandar Abbas. The level of Hg accumulation and its interaction with Zn and Se in Whitecheek Shark were studied. Hg, Zn and Se concentrations were determined by an Advanced Mercury Analyzer (LECO, AMA 254), Atomic Absorption Spectrometer (ASS,PU 9400) and Graphite Furnace Atomic Absorption Spectrophotometry (Perkin Elmer 3030) respectively. The mean (±SD) of Hg, Zn and Se concentrations were 0.05±0.02, 0.92±0.25 and 0.13±0.05μg/g wet wt in the muscle and 1.07±0.86, 1.57±0.43 and 0.46±0.19μg/g wet wt in the liver tissues, respectively. The mean of Hg, Zn and Se in liver tissue was significantly higher than muscle tissue. Also, 64% of liver samples showed levels above the acceptable limit established by WHO and FAO. A positive correlation was found between Hg and Se concentrations in the muscle and liver tissues with weight and length variables were statistically significant. In this study, the accumulation of Se in the muscle and liver of Whitecheek shark showed a positive correlation with Hg concentration. The mean molar ratio of Se to Hg found in the muscle and liver were 6.36±1.77 and 2.74±3.61, respectively. Positive correlations between Hg and Se showed efficient detoxifying mechanism and as a result, the possibility of reduction in

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Mercury causes oxidative stress in the body by producing oxygen free radicals and destroying antioxidant sources. The most important application of selenium is its role in the construction of antioxidant enzymes such as glutathione peroxidase, the function of which is to eliminate free radicals and reactive oxygen species. The aim of this study was to investigate the antioxidant effect of selenium nanoparticles and sodium selenite on biochemical parameters and antioxidant defense in Acanthopagrus latus in the presence of mercury chloride. A total number of 300 fish (25±3 g) were randomly distributed in five groups according to diet: control, nanoSe and sodium selenite (1 and 1.5 mg/kg). Fish were fed with experimental diets for six weeks. They were then exposed to a sublethal dose of HgCl₂ for two weeks. At the end of the feeding period and after exposure, blood and liver samples were taken from all treatments and the activity of liver enzymes and antioxidants were measured. After six weeks of feeding the results showed that the form of selenium nanoparticles improved growth performance, increased the activity of antioxidant enzymes GPX and CAT and reduced the content of MDA, AST and ALT (p<0.05). The results showed that the form of selenium nanoparticles was more effective than the inorganic form of selenium during the period of exposure in increasing the activity of the antioxidant enzymes GPX and CAT. Decreased MDA content in the liver of fish fed selenium nanoparticles indicated a reduction in lipid peroxidation and a reduction in oxidative stress. The activity of ALT, AST and ALP enzymes increased more in the groups fed with selenium sodium than in the groups fed with nanoparticles (p<0.05). This study showed that the addition of selenium nanoparticles to the basic diet was more effective in terms of growth and antioxidant indices in yellowfin porgy (A. latus) after exposure to mercury chloride.

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Haraz River has an important role in the development of aquaculture and the production of rainbow trout in Mazandaran province. Since 2015, the production of rainbow trout has been decreased in the farms along the river and almost halved. This study have been investigated the microbial indices and heavy metals in water as well as the identification of common bacterial pathogens and their resistance to antibiotics and used them as effective factors in the fish health and production. This study was conducted during four seasons (summer, autumn and winter 2017 and spring 2018) in 6 rainbow trout farms along the Haraz River. The results showed that the amount of the water mercury in all seasons was from minimum 2 to maximum 12 times the allowable limit but the arsenic level was standard in all sampling times. The most important clinical symptoms were observed in the fish including fin rot, erratic swimming, inflammation and hyperemia of the liver and kidneys. From 420 fish with clinical signs, 12.15% and 87.85% of fish were positive and negative bacterial culture respectively. The all of bacterial isolates were gram-negative and no gram-positive bacteria were isolated. The bacterial agents identified were including, Yersinia (37.25%), Aeromonas (33.35%), Eduardzilla (11.76%), Vibrio (7.84%), Pasteurella (5.88%) and Citrobacter (3.92%). The highest and lowest antibiotic resistances were found against amoxicillin and trimethoprim sulfamethoxazole respectively. In evaluation of the microbial water indices including total bacterial count, coliform count, fecal coliform count and E. coli, the results showed that the all of microbial indices were not allowable level in the most of the sampling time. 

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This research was conducted with the aim of measuring and investigating the relationship between heavy metals (mercury and zinc) and some biochemical factors of blood and gill tissue of sea bass (Lates calcarifer) grown in cages in fall of 2022, located in Kangan port. After fixing the samples with alcohol, they were transferred to the laboratory. The biometric indexes of the fish including weight in grams were measured using a scale and total length in centimeters using a biometric board. Then, a sample of the gills of each piece of fish was prepared and the concentration of each metal was obtained by flame atomic absorption spectrophotometry. To evaluate histological analysis, gill tissue samples were separated and stained by hematoxylin and eosin method. Blood biochemical factors were measured according to the instructions of the commercial kit. The results of this research showed that the average metal mercury and zinc were 0.1 and 7.5 microgram/g respectively in the fish blood serum of the samples. which was lower than WHO and FAO standards. The average concentration of cortisol, glucose, albumin, total protein, cholesterol and triglycerides were 50.55 ng/l, 154.33 mg/ dl, 1.19 g/dl, 3.36 g/dl, 194 mg/dl and 244 mg/dl were obtained, respectively. In the examination of the gill tissue sample of Asian seabass, complications such as hyperemia, bleeding, hyperplasia, cell necrosis and destruction of the epithelium layer of the primary and secondary strands of the gill were observed. The concentration of heavy metals mercury and zinc in the gill tissue of the studied seabass was lower than the standard limit determined by FAO and WHO.