In-Transit Oxytetracycline Marking, Nonlethal Mark Detection, and Tissue Residue Depletion in Yellow Perch

Abstract

Trapping and transfer of juvenile and adult yellow perch Perca flavescens is conducted to fulfill perch stocking needs in South Dakota. To determine the utility of oxytetracycline (OTC) hydrochloride marking as an assessment tool for yellow perch stockings, we investigated a transfer tank marking protocol, compared OTC mark detection in dorsal spines with that in sagittal otoliths, and assayed the depletion of OTC residues in adult yellow perch muscle tissue. Juvenile yellow perch were immersed for 4, 6, or 8 h in 500 or 700 mg OTC/L at 18°C in transfer tanks. Acute mortality was less than 1% at 8 h. At 3 months postimmersion, fluorescent marks were detected on all spine sections and otoliths from fish treated for 6 h or longer. Mark quality was observed to be slightly better in juvenile dorsal spines than in otoliths. Adult yellow perch were immersed for 6 h in 600 mg OTC/L at 19°C. Marks were initially detected at otolith margins at 9 d postimmersion but were best detected on all otoliths after 51 d postimmersion. High pressure liquid chromatography of adult yellow perch muscle tissue indicated that OTC was rapidly depleted; the acceptable tolerance level of 2 μg total OTC residue/g for human consumption was reached by about 2 h postimmersion. The nonlinear relation between total residue (OTC base and 4-epioxytetracycline) and time was defined by the equation log _e total(OTC) = 0.960 − 0.389·log _e (time) (r ² = 0.99).