The Use Of Oxytetracycline As A Chemical Mark In Pacific Coast Salmon

Abstract

Coho salmon (Oncorhvnchus kisutch) fry were fed oxytetracycline (OTC) medicated food so that the OTC would be deposited in the bones of the growing fish. The objective was to evaluate the use of OTC deposited in the bone as an internal mark or tag. The study relied upon a fluorometric procedure developed by Koenings and Lipton (1983) to detect this internal mark. The method involves the extraction of OTC from the bones of the fish, and the subsequent measuring of the fluorescence of the OTC-calcium complex. A linear relationship was found between the concentrations of OTC and fluorescence in both samples containing biological material and those without biological material. However, in contrast to earlier work (Koenings and Lipton, 1983) a linear relationship between OTC and fluorescence was not found to be the same for the samples with and without biological material. The fry were fed OTC medicated food for 45 to 50 days after which time they were taken off the medicated food for 15 days before they were sacrificed. Upon fluorometric examination of these fish, no OTC mark could be detected in any of them. This is another deviation from earlier work (Koenings and Lipton, 1983) in which an OTC mark was detected in the medicated fish.