Open Access The Influence of Symmetrical Feed:Fast Regimes on Oxytetracycline Up- take and Otolith Score in Yellow Perch

Abstract: Periods of growth from symmetric feed:fast regimes (i.e., days fed followed by the same number of days fasted) may increase the uptake of oxytetracycline (C22H24N2O9.HCL[OTC]) compounds in fishes; however, little empiri-cal data exists. Therefore, we experimentally determined if such feeding regimes influenced the concentration of OTC in-corporated in muscle and skeletal (e.g., otoliths) tissues. Individually-reared female and batch-reared (male and female), age-1 yellow perch Perca flavescens were subjected to one of four experimental feeding regimes: control (i.e., fed daily), D2 (i.e., 2d feed, 2d deprivation), D6, or D12 symmetrical feed:fast regimes. Following several feeding cycles on these feeding regimes, fish were submersed in a 600mg/L buffered OTC solution; otoliths and muscle tissue were excised and processed to determine OTC uptake via mark quality and concentrations. Ranked otolith scores (mark quality) were sig-nificantly lower for the D2 feeding regime than control, D6, and D12 scores for both individual and batch trials suggesting that frequent food deprivation restricts osteogenesis, while daily or extended feeding periods contribute to osteogenesis. In batch-reared fish, total OTC and 4-epioxytetracycline peak concentrations in muscle tissue did not significantly differ among treatments but were significantly greater for smaller individuals within treatments suggesting that the OTC uptake and elimination response is mechanistically related to higher gill ventilation volume and gastric ingestion rate of small fish providing increased chemical assimilation and decreased clearing time following OTC immersions. Increased otolith mark quality derived from such feeding protocols may be of particular interest to fisheries managers conducting stoc