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 (delta C-13) and nitrogen (delta N-15) isotope ratios for muscle, fin, and liver. The trophic enrichment values were ranked liver < muscle < fin for delta C-13 (range -0.80e to +3.66e) and liver < fin < muscle for delta N-15 (+0.59e to +3.12e). The half-life values were similar for muscle and fin for both delta C-13 and delta N-15 (19.3-25.7 days), while those for liver were 5.3 days for delta C-13 and 14.4 days for delta N-15. Both the delta C-13 and delta N-15 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.