Data from: Arithmetic normalization models for the effects of lipid on carbon stable isotope values in silver carp (Hypophthalmichthys molitrix) tissue

Invasive silver carp (Hypophthalmichthys molitrix) threaten Mississippi
River basin ecosystems due to their ability to outcompete native species.
Stable carbon (δ13C) and nitrogen (δ15N) isotope analysis has been used in
prior studies to help identify how silver carp impact native ecosystems,
however lipids in fish tissues commonly bias their δ13C values. Chemical
lipid extraction and mathematical equations that normalize δ13C values for
lipid content are common ways to account for the effect of lipid on tissue
stable isotope values in fish, though species and tissue-specific
arithmetic models have not yet been derived for silver
carp. Using paired t-tests, we assessed differences in δ13C,
δ15N, and C:N ratios before and after chemical lipid extraction in muscle
and whole fish from silver carp collected along three sites in the
Mississippi River. We then used linear and natural log models to estimate
lipid-extracted δ13C values in carp muscle and whole fish samples based on
their non-lipid-extracted δ13C values and elemental C:N ratios. We
evaluated these arithmetic models for best fit and parsimony and used
paired t-tests to assess accuracy between mathematically normalized and
chemically lipid-extracted δ13C values. We found that chemical
lipid extraction increased silver carp δ13C values and decreased C:N ratio
in muscle and whole fish as well as increasing δ15N values in whole fish
but not fish muscle. While both linear and natural log regression models
accurately estimated lipid extraction δ13C in both sample types, the
natural log approach provided better model fits and greater parsimony
throughout the wide range of C:N ratios observed in silver carp. Our
results confirmed the need to account for lipid-effects on δ13C values in
silver carp tissue. Moreover, the arithmetic models provided by our study
will allow future researchers to conduct stable isotope analysis on silver
carp without the added time and cost of chemical lipid-extraction. In
addition, the positive relationship we identified between fish muscle and
whole fish will facilitate the comparison of stable isotope values in
silver carp across studies.