| Disease outbreaks among cultured sturgeon yearlings have brought great loss to sturgeon husbandry. The thesis presented here is aim to find out the cause of the disease. After investigation we knew the morbidity and mortality, presenting signs, progression of disease and then carried out the study on the disease. The results are below. The primarily examination didn't find out any bacteria and parasites. Sturgeon juveniles were experimentally challenged with the tissue extract from disease sturgeons. But there are no lethal disease in the result. No suspected virus or fungi was found in liver, speen, kidney and brain by tissue pathogen microbial determination. We also found that prevent and therapy with antibacterial and antiviral have no obviously effect. But the health sturgeons were infected after 9 days when they were placed with disease sturgeon. In the experiment, which healh sturgeons were only given with artifical feed or was starved, we found the starvation caused by refusing the feed maybe evoke or accelerate the disease. We concluded the heavy metal which was traced to water worms, was attributed to the disease after detecting the content of heavy metal in cultivation water, water worms and disease sturgeons tissues. The content of Hg, Pb and Cd especially Hg is very high. Exposure of Amur Sturgeon (Acipenser schrencii Brandt) to Hg for acute and chronic toxic experiment showed that the median lethal concentrations (LC50, 96h) of sturgeon is 0.50145 mg/L, and threshold dosage is about 0.515 mg/L, Inefficiency dosage is 0.0515 mg/L in the long-term exposure. In the chronic toxic experiment, we also found some diseased fish show partially similar sign to the disease outbreak. From all the experiment, we can conclude that some unknown virus agent may be the cause of the disease, and heavy metal poisoning is an important factor to the disease , and the pathogenesis can exclude bacteria, parasites, fungi. Further study on the virus opportunit need to be done.
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