Turnover rates for muscle, mucus and ovary tissues of ayu fish (Plecoglossus altivelis altivelis) in multiple stages determined through carbon and nitrogen stable isotope analyses

Abstract

AbstractStable isotope ratios are powerful indicators that facilitate the understanding of the diet shifts and between‐habitat migration of aquatic animals. However, isotopic change rate can be variable even between the life stages of a single species, which affects field data interpretation. We conducted diet‐switch experiments to compare the δ13C and δ15N changes in multiple tissues between the growing and reproductive stages of ayu fish (Plecoglossus altivelis altivelis). Isotopic changes in the muscle and mucus tissues were faster in the growing stage than in the reproductive stage. Isotopic change in the muscle tissue during the reproductive stage was caused mainly by whole‐body growth, whereas allometric growth and/or catabolic turnover rather than whole‐body growth accounted more for the isotopic changes in mucus tissue during both stages. Isotopic change was slower in muscle, mucus and ovary tissues, in that order, probably according to the allometric growth and/or catabolic turnover of each tissue. Our investigation showed that the timing of drastic changes differed between the δ13C and δ15N values, as the first report of the isotopic change in the fish ovary tissue, which suggests that the δ13C and δ15N values in the ovary tissue may reflect diets and/or habitats of different time scales. Trophic discrimination factors varied between tissues examined. Our results allowed for accurate applications of multiple‐tissue isotope analysis to our target fish over all stages. Such approaches to any fish species are more accurate when considering the variability of isotopic changes between and within stages.