• Journal of Aquaculture
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• v.10 no.1
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• pp.1-7
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• 1997

In the southern sea of Korea, the culturing Rock bream, Oplegnathus fasciatus, ranging from 16.3 to 20.1cm in body length were sampled to examine how serious parasitic infection is. As a result, they were infected with 10 to 31 individuals of Monogenea, Benedenia sp. The parasitic sites of fish body was trunk (81.8%), caudal peduncle (16.5%) and the other portion (1.6%), and where ulceration and bleeding were observed with a large amount of muscus. When the treatment with formalin and freshwater were performed to get rid of the parasite, they were exterminated after 8 and 20 minutes in 100% and 70% freshwater, respectively and were killed after 10, 15 and 20 mimutes in the seawater added with formalin to be 250 ppm, 200 ppm and 150 ppm, 200 ppm and 150 ppm, respectively. During the treatment for parasite extermination, the fish showing a serious illness were dead in the 100% freshwater, whereas toxicity caused by formalin treatment was not detected in this study. The former is probably due to failure in the osmotic regulation of Rock bream.

• Journal of Aquaculture
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• v.11 no.3
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• pp.285-294
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• 1998

When Cochlodinium polykrikoides came into the culture tanks through influent cultivated water during the red tides, hundred thousands of commercial flounders were concomitantly killed and many culturists suffered from a great deal of financial loss in the east coast of Korea. It is charactrized by high sinking rate after sunset and the formatino of clump which results in oxygen deficiency by its respiration at tank bottom under condition. We investigated the efficacy of hydrogen peroxide and chlorine dioxide, known to form radicals, for extermination of red tide organism C. polykrikoides. When C. polykrikoides seawater with a density of 6,000 cells/$m\ell$ was treated with 14, 28 and $42mg/\ell$ of hydrogen peroxide, its survival rate was markedly decreased to 9.8, 0.8 and 0.3% respectively immediately after 6 hours of treatments whereas when it was treated with 1.5, 2.1 and $3.0mg/\ell$ chlorine dioxide, its survival rate showed 87.7, 81.3 and 80.1 and 80.1% respectively at the same treatment time. Hydrogen peroxide was the effective agent since it has scarcely injured the cultured olive flounder when exposed to the tested concentration range of $14~28mg/\ell$ with the extermination of almost3 C. polykrikoides during the experimental period of 5 days and has shown the oxygen increase of approximately $1.23mg/\ell$ 2 hours immediately after the flounder by C. polykrikoides in the land-based culture tank is assumed to be not by the toxicity of itself but by oxygen dificiency from the rapid respiration of dinoflagellate clump sunken to the tank bottom.