1. Stable isotopes represent a unique approach to provide insights into
the ecology of organisms. δ13C and δ15N have specifically be used to
obtain information on the trophic ecology and food web interactions. The
trophic discrimination factor (TDF, Δ13C and Δ15N) describes the
isotopic fractionation occurring from diet to consumer tissue and this
value is critical to obtain precise estimates within any application of
δ13C and δ15N. It is widely acknowledged that metabolism influences the
TDF, being responsible for different TDFs between tissues of variable
metabolic activity (e.g. liver vs. muscle tissue) or species body size
(small vs. large). However, the connection between the variation of
metabolism occurring within a single species during its ontogeny and
TDFs has rarely been considered. 2. Here, we conducted a 9-month feeding
experiment to report Δ13C and Δ15N of muscle and liver tissue for
several weight classes of Eurasian perch (Perca fluviatilis), a
widespread teleost often studied using stable isotopes, but without
established TDFs for feeding on a natural diet. In addition, we assessed
the relationship between the standard metabolic rate (SMR) and TDFs by
measuring their oxygen consumption of the individuals. 3. Our results
showed a significant negative relationship of SMR with Δ13C, but not
with Δ15N of muscle or TDFs of liver tissue. SMR was significantly
higher in perch juveniles, which translated to significantly lower Δ13C
of muscle tissue. 4. In summary, our results emphasize the role of
metabolism in shaping specific TDFs (i.e. Δ13C of muscle tissue), and
especially highlight the substantial differences between individuals of
different ontogenetic stages within a species. Our findings thus have
direct implications for the use of stable isotope data and the
applications of stable isotopes in food web studies.
The Effect of Parasite Infection on Stable Isotope Turnover Rates of δ15N, δ13C and δ34S in Multiple Tissues of Eurasian Perch Perca fluviatilis
