RESIDUES OF CLENBUTEROL IN TISSUES OF THE RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

There have been many studies on the efficacy of beta2-adrenergic drugs as feed additives but no data are available at present on the use of clenbuterol in fish production. To evaluate the residues of clenbutero l in tissues of fish, 50 trout (Oncorhynchus mykiss) were fed for 21 d ays on a fish feed containing 5 ppm of the drug. The livers, muscles a nd skins of sample groups of fish were analysed by HPLC with visible s pectrophotometric detection on days 15 and 21 of treatment and at inte rvals during a 30-day withdrawal time. Clenbuterol reached its highest levels in the liver (mean 440 ppb; SD = +/- 159; n = 5) on day 15 of treatment, with a slow depletion curve; 24 +/- 3 ppb was still present at the end of the withdrawal period. At this time, residues were stil l present in the edible tissues, i.e. muscle (5 +/- 1 ppb) and skin (7 +/- 3 ppb). Side-effects were noted during the first week of treat