Toxicological Studies on Fish

The Present work aimed to investigate the toxicity and hazard of some pollutants on fish. Data revealed that:1. The Acute toxicity of six insecticides Viz., lambda- cyhalothrin, methomyl, thiodicarb, chlorpyrifos, buprofezin and pyrazosulfuron against two sizes of Nile Bolti fish (Oreochromis niloticus), 1 and 5 gm body weight was evaluated. It was found that lambda- cyhalothrin was the highest toxic insecticide, while pyrazosulfuron was the lowest toxic one.2. Exposure to lambda-cyhalothrin at sublethal concentration induced biochemical changes in serum of Nile Tilapia. Also the histopathological effects of a sublethal concentration of lambda-cyhalothrin on fish tissues were investigated. Data revealed several changes in fish tissues compared with control. 3. The levels of six heavy metals Viz., Pb, Cd, Cu, Fe, Mn, and Zn in different aquatic sites were determined. It was found that Bahr El-Backer stream contained the highest amounts of the tested heavy metals while El-Bardaweel lake contained the lowest levels of metals in Nile and catfish muscles. The intestine and gills contained higher amount of heavy metals compared with muscles. 4. The levels of sex hormones in fish and water indicated that fish and the ambient water obtained from different streams were contaminated with the two sex hormones (progesterone and testosterone). The visceral fat tissue contain the higher amounts of both hormones compared with the muscles tissues. Sex hormones may cause disrupt in reproduction, somatic cell function, sexual differentiation and ovulation.