The impacts of ontogenetic dietary shifts in yellow perch (Perca flavescens) on Zn and Hg accumulation

Yellow perch (Perca flavescens) undergo several ontogenetic dietary shifts, and consequently these fish feed at different trophic levels and rely on different carbon sources over their lifetime. Stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) are powerful ecological tools that are used to provide a temporally integrated description of the feeding ecology of aquatic animals such as fish. The main objective of this study was to use stable isotopes of nitrogen and carbon to determine if dietary changes affected mercury (Hg) and zinc (Zn) accumulation in yellow perch ranging in size from approximately 5 cm to 27 cm. Results showed that Hg bioaccumulation generally increased with increasing trophic level in fish feeding at higher trophic levels, however, the relationship between Hg levels and δ15N was non-linear showing no relationship in small fish (less than 15 cm). In contrast, there was a negative, linear relationship between δ15N and Zn, suggesting that as perch fed at progressively higher trophic levels, less of Zn bioaccumulated. No relationship was observed between δ13C and metal levels in perch. Collectively, these results demonstrate a contrast in the behavior of Zn and Hg bioaccumulation in yellow perch as a function of trophic status.

► Relationship between zinc and mercury accumulation in yellow perch and diet.
► Nitrogen and carbon stable isotopes used to describe feeding ecology.
► Non-linear relationship between nitrogen ratios and mercury.
► Negative relationship between nitrogen ratios and zinc.
► No relationship between carbon isotopes and either metal.