Turnover rates of carbon and nitrogen stable isotopes in juvenile marbled flounder Pleuronectes yokohamae estimated by diet switch

Abstract

Many fish species generally migrate among habitats because of ontogenetic changes in their resource requirements; therefore, clarifying linkages among habitats throughout their life cycle is important for the management and conservation of their populations. Although carbon (δ13C) and nitrogen (δ15N) stable isotope ratios are widely used for elucidating fish migrations, information is still scarce how each fish species, including marbled flounder (Pleuronectes yokohamae), change the isotopic composition in their body tissues after they switch to a different diet during migrations. This study clarified isotopic turnover rates of marbled flounder during the juvenile stage using a diet-switch experiment in an aquarium. Furthermore, we statistically compared bulk samples (i.e., whole body without head and viscera) to partial muscle tissue samples to estimate the difference in the turnover rate as an index for diet switches. An exponential model was used to describe the temporal changes in δ13C and δ15N isotopic rates of juvenile marbled flounder. No significant difference was noted between the exponential models for changes in both δ13C and δ15N between muscle tissue and bulk samples, and the half-life values were similar for muscle and bulk samples for both δ13C and δ15N (14.0–18.5 days). These results suggest that bulk samples are a useful substitute for muscle tissues in isotopic analysis of juvenile fish and that stable isotope analysis and the estimated isotopic turnover rates in tissues of marbled flounder can be used to clarify their migration route in coastal areas.