Fish muscle tissue samples were dried at 60 °C for 24 h, ground into fine powders using an Agate (SiO2) mortar and pestle, and packed into tin capsules for solid samples. Stable C and N isotope ratios were measured at The Ohio State University Stable Isotope Biogeochemistry Laboratory using an elemental analyzer (Costech Analytical Technologies,Inc.) coupled to a Finnigan Delta IV Plus isotope ratio mass spectrometer (Thermo Fisher Scientific, Inc.) under continuous gas flow using a CONFLO III interface (Thermo Fisher Scientific, Inc.). Samples were measured relative to C and N reference materials and 10% of the samples were measured in duplicate. Stable isotope measurements are expressed using the standard delta (δ) notation, defined as parts per thousand (‰) deviation in isotope ratios from the Vienna Pee Dee Belemnite limestone (C) and air (N) international standards. The average standard deviations for repeated measurements of the USGS24, IAEA-N1 and IAEA-N2 standards were 0.05‰for δ13C and 0.14‰for δ15N. The average standard deviations for duplicate fish tissue measurements were 0.04‰ for δ13C and 0.09‰for δ15N.