Individual variability in stable isotope turnover rates of epidermal mucus according to body size in an omnivorous fish
Emily R. Winter, J. Robert Britton
Abstract
Abstract Epidermal mucus (‘mucus’) is increasingly applied to fish ecological studies based on stable isotope analysis (SIA) due to its non-invasive collection. However, knowledge on mucus SI turnover rates of individual fish remains limited, including uncertainty over how they are influenced by fish body sizes. Here, a diet switch experiment predicted mucus SI turnover rates (δ 13 C and δ 15 N) as a function of time using samples taken over 200 days from 10 individually tagged common carp Cyprinus carpio covering two size groups. Non-linear mixed effects models revealed rapid turnover of both δ 13 C and δ 15 N ( T 50 : 2–5 days; T 95 : 9–22 days); δ 15 N turnover rates were slower for the larger cohort, while δ 13 C turnover rates were independent of body size. Within size groups, turnover rates were not expected to vary between individuals. These experimental results suggest that due to these fast turnover rates, epidermal mucus can provide insights into the diets of fish over very short timeframes, although for δ 15 N the body size of the fish needs consideration.