Differential isotopic enrichment and half-life among tissues in Japanese temperate bass (Lateolabrax japonicus) juveniles: implications for analyzing migration

As a first step for field applications of stable isotope techniques to investigate the migration of Japanese temperate bass (Lateolabrax japonicus) (Perciformes) juveniles, we conducted a diet switch experiment and fitted an exponential model to changes in stable carbon (δ13C) and nitrogen (δ15N) isotope ratios for muscle, fin, and liver. The trophic enrichment values were ranked liver < muscle < fin for δ13C (range –0.80‰ to +3.66‰) and liver < fin < muscle for δ15N (+0.59‰ to +3.12‰). The half-life values were similar for muscle and fin for both δ13C and δ15N (19.3–25.7 days), while those for liver were 5.3 days for δ13C and 14.4 days for δ15N. Both the δ13C and δ15N values of muscle reached the asymptotic value after a threefold body weight increase, reflecting the diet after the switch. These results suggest that fin is a useful substitute for muscle in field applications of stable isotope techniques and that liver, with a shorter half-life, has the potential to provide more recent information about migration.