대청댐 서식어류의 병원생물에 관한 연구

Studies on the pathogenic organisms detected from the fish in Daechung Dam

To understand the occurring status of fish diseases in the wild and cultured fish of Daechung Dam from November to December, 1995, July to October 1996, and March to June 1997, the detection of pathogenic organisms from the fish was conducted and the environmental factors such as water temperature, pH, D.G and transparency were also investigated. The water temperature changed from 8.8℃(March) to 34.3℃(August) in dam water and from 9.8℃ (March) to 34.8℃ (August) in fish-farm water. Dissolved oxygen varied from 3.4 mg/ℓ (September) to 15.2mg/ℓ (March) in dam water and from 4.5mg/ℓ (September) to 15.5mg /ℓ (March) in fish-farm water. pH varied from 6.7(October) to 9.7(June) in dam water and from 7.3(October) to 9.3(August) in fish-farm water. Transparency varied from 1.4m(july) to 3.5m(March) in dam water and from 1.1m(July) to 2.3m(March) in fish-farm Water. From the wild fish 6 species of pathogenic organisms were detected, and they were consist of three protozoans, two plathelminthes and one parasitic copepods. The infection rate of Dactyrogyrus sp. was the highest(11.3%) and those of Myxobolus sp., Trichophyra sp., Bothriocephalus sp., Trichodina sp., and Pseudoergasilus sp. were 3.0%. 0.3%, 0.2% and 0.09%, respectively. From the culture fish 9 species of pathogenic organisms were detected and they were consist of four protozoans, one plathelminthes, one parasitic copepods and two bacteria and one fish mold. Trichodina sp. showed the highest(20.8%) in the infection rate and the rates of Dactyrogyrus sp., and Myxobolus sp. were 15.6% and 14.9%. Thellohanellus sp., Epistylis sp. and Argulus sp. were 10.4%, 2.6%, and 2.4%, respectively. The rates of Aeromonas sp. Flexibacter sp. and Saprolegnia sp. were 14.3%, 2.4%, and 3.6% respectively. Twelve species of pathogenic organisms were detected from the wild and cultured fish in Daechung Darn. Both the species and infection rates of pathogenic .organisms in the cultured fish were higher than those in the wild fish. Therefore it is concluded that pathogenic organisms of the wild fishes were transmitted to the cultured fish due to the active growth of them in fish-farm.