Study On Acute Toxic Effect Of Water-born Cadmium On Six Common Fishes In The Upper Reaches Of The Yangtze River

To investigate the acute toxic effects of waterborn Cadmium(Cd) on 6 common fishes in the upper reaches of Yangtze River, the juveniles of Carassius auratus, Ctenopharyngodon idellus, Megalobrama amblycephala, Myxocyprinus asiaticus, Silurus meridionalis and Spinibarbus sinensis were exposed to Cd with different concentrations, at a same water temperature(27.5±0.5℃), pH(7.0±0.1) and hardness(10±0.5 mg/L CaCO3), observing the water at different concentrations Cd exposure on symptoms of acute poisoning fish and 96 h experimental lethal effects(96hLC50), and measured six fish measured Cd accumulation conditions by atomic spectrophotometer.The main results are as follows:1. The results showed that behavioral responses was different among the six species under water-born Cd exposure Carassius auratus, Ctenopharyngodon idellus, Megalobrama amblycephala and Spinibarbus sinensis showed were active in jumping out of the water surface tendency during the initial stage of the experimental treatment, and their activities were depressed gradually with the exposure time lasting. Carassius auratus, Ctenopharyngodon idellus, Silurus meridionalis had cough responses during the exposure.2. The mortalityof experimental fish increased with increasing Cd concentration. The median lethal concentration in 96 hours(96hLC50) of Cd to Carassius auratus, Ctenopharyngodon idellus, Silurus meridionalis, Megalobrama amblycephala, Spinibarbus sinensis and Myxocyprinus asiaticus were 5.59, 2.53, 2.24, 1.51, 1.31 and 0.029mg/L respectively.3. Cd accumulation in the dead fish was lower than that in the survivors in each species except for Silurus meridionalis. And the difference between the dead fishs and the survivor fishs reached significant level in Spinibarbus sinensis(P < 0.05).The conclusions suggested in this study were as follows:1. Waterborne Cd exposure can significantly affect behavior of fish, and thebehavioral response of fish to Cd exposure is difference.2. Carassius auratus which broader distribution and adapt to a variety of the ecological environment(cold resistance, hypoxia), can growth and multiply in the environment of other fish can not survival. C. auratus have most tolerance to heavy metals Cd, which may be one of the reason strong ability to adapt to the environment and wide distribution. Megalobrama amblycephala is very low tolerance for Cd, it may be difficult to survive in increased pollution of the water environment, one of the reasons for endangered species.3. In comparison with the tolerance of different fish species to the same heavy metal, the body weight of fish and water hardness must be considered.4. Cd accumulation in the dead fish was lower than that in the survivors in each species except for Silurus meridionalis, while the other five experiments on fish body opposite to the observed phenomena. Cd into the water body surface and gills of fish, mainly through the death of fish gills thus stopped breathing passage is closed. Comparison southern catfish skin structure is more densely, rich surface mucu. It was suggested that the skin structure and its rich mucus might prevent Cd ions entering into the body through the skin. It will not because it is not the death of fish in the water and soak for a long time to penetrate Cd significantly increased.