Oxytetracycline tags in pink salmon fry applied by immersion and detected by fluorescence spectrometry

Abstract

I investigated the feasibility of using spectrophotofluorescence as a quantitative method of analyzing pink salmon fry otoliths for the presence of oxytetracycline (antibiotic). I exposed twenty-four groups of pink salmon fry (approximately 250 individuals each) to solutions of oxytetracycline ranging in concentration from unexposed to 2000 ppm, and in duration of exposure from one to twelve hours. Otoliths from unexposed fry had the lowest mean fluorescence (log e [mean flu. units] = -1.77). Otoliths from fry exposed to 500 ppm for twelve hours had the highest fluorescence (log e [mean flu. units] = 0.899). Fluorescence increased nonlinearly with duration of exposure. There is a linear increase of fluorescence with exposure up to 500 ppm; above which fluorescence decreases. Pink salmon fry exposed to OTC in solution absorb detectable amounts of OTC in their otoliths. These amounts of OTC can be quantitatively measured by spectrofluorometry.