IMPACT OF ADMINISTERING ANTIBACTERIAL AGENTS ON WILD FISH AND BLUE MUSSELS MYTILUS-EDULIS IN THE VICINITY OF FISH FARMS

Using high-performance liquid chromatography, residues of the quinolon es oxolinic acid and flumequine have been quantified in muscle of wild fish. The fish were caught 0 or 1 d after terminating medication in t he vicinity of 6 fish farms previously employing one of the drugs. The majority of the wild fish (74 to 100 % of the catch at the different farms) contained drug residues in muscle. The mean muscle concentratio n varied from 0.95 to 4.89 mug g-1 (ppm). Using a standard microbiolog ical method, 60 % of the examined fish were found to contain faecal ma terial displaying antibacterial activity. The occurrence of bacteria r esistant to oxolinic acid and oxytetracycline in blue mussels Mytilus edulis and in the intestinal content of fish was also examined. The le vel of resistant bacteria was higher in samples taken at the farm afte r medication than in samples collected before medication or from untre ated areas.