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A high-performance liquid chromatography assay method for oxolinic acid in fish products was developed, evaluated and validated through the monitoring of oxolinic acid based on farming and distribution. The recovery rate of the developed method was as compared to conventional methods. The stock solution was stable for 3 weeks under refrigerated condition at The performance limit was evaluated as 0.01ppm of oxolinic acid in fish muscle. 478 fish samples such as olive flounder, genuine porgy, common sea bass and black rock fish collected from fish farms in the coastal area from September 2001 to October 2004 were analyzed to evaluate overall efficiency of the modified method and to monitor the actual condition of oxolinic acid usage in fish farm. According to the monitoring results, the modified method was suitable for analysis of oxolinic acid in fish muscle and oxolinic acid might be used in a small portion of fish farms. The suggested analysis method of oxolinic acid was registered in the Korean Official Methods of Food Analysis and is being utilized for fishery products by the Korea Food and Drug Adminstration and the National Fisheries Products Quality Inspection Service.

The distributions of sanitary indicative bacteria and pathogenic bacteria in seawater and four species of farmed fishes, including oliver flounder (Paralichthys olivaceus), black rock fish (Sebastes schlegeli), red sea bream (Pagrus major) and sea bass (Lateolabrax japonicus), collected at fish farms located in the southern coastal area of Korea were investigated from May to October in 2004. The detection rates of fecal coliform and Entirococcus spp. of sanitary indicative bacteria in all samples were and , respectively. The occurrence of fecal coliform was highest of in Busan, Geoje and Wando area, followed Yeosu , Jeju , Tongyeong . The occurrence of Enterococcus spp. was highest In Wando area (), followed by Yeosu (), Tongyeong (), Busan (), Geoje and Jeju (). The detection rate of fecal coliform was higher than that of Enterococcus spp., except in the Tongyeong area. There was no difference in the detection rate of fecal coliform from May to October, but the detection rate of Enterococcus spp. increased with seasonal warming seawater temperature. Among the pathogenic bacteria, the detection rate of Vibrio alginolyticus () in all samples was highest, followed by V. parahaemolyticus (), Staphylococcus aureus (), Salmonella sp. (). However, V cholerae, V. vulnificus and Shigella sp. were not detected in all tested samples. The detection rates of V. parahaemolyticus and V. alginolyticus increased with seasonal warming seawater temperature from May to August.

An analysis method of tetracyclines far fish and shellfish products containing large amount of low molecular materials and pigments was established. The recovery of the established analysis method for four tetracycline samples was and higher than other methods reported. Especially, proposed sample treatment protocol was shown to be effective for the removal of low molecular materials and pigments that tend to interfere with accurate analysis. The detection limit of oxytetracycline (OTC) and tetracycline (TC) from the sample was 0.02 ppm, and the detection limit of chlortetracycline (CTC) and doxycycline (DC) from the sample was 0.1ppm, To examine the efficiency of the established method and identify tetracycline usage in fish farms, tetracycline group antibiotics in the flounder being cultured was monitored. The improved method can be used for fish and shellfish products effectively and all surveyed fish farms have used tetracycline all the year round. The proposed method was adopted as official method for fishery products by Korean Food and Drug Administration in 2003 and it is being used by regulatory authority as National Fishery Products Quality Inspection Service.

The antimicrobial resistance patterns to the 10 antimicrobial agents of potential pathogenic vibrios isolated from seawater and a variety of farmed fishes, including oliver flounder (Payalichthys olivaceus), black rock fish (Sebastes schlegeli), red sea bream (Pagyus major) and sea bass (Lateolabyax japonicus), were investigated from May to October, 2004. A total of 314 strains of the genus vibrios were isolated from 126 collected samples, and the number of isolated strains of Vibrio payahaemolyticus and Vibrio alginolyticus were 194 and 120, respectively. Apparently of V. parahaemolyticus and of V. alginolyticus isolates demonstrated antimicrobial resistance against at least one antimicrobial agent. The resistance of V. parahaernolyticus isolates to ampicillin () was highest, followed by oxolinic acid (), amikacin () and tetracycline and amoxicillin/clavulanic acid (). V. alginolyticus isolates were resistant to ampicillin (), solfamethoxazoleit,imethopenem (), amikacln (), amoxicillin/clavulanic acid (), ciprofloxacin (), and tetracycline and doxycycline (). The rate of multiple antimicrobial resistance to at least four antimicrobials was higher in the V. alginolyticus isolates () than in the V. parahaemolyticus ().