Trophic inferences of blue shark (Prionace glauca) in the Mexican Pacific from stable isotope analysis in teeth

RATIONALE Isotopic analysis of biogenic tissues such as teeth of elasmobranchs has been well recognized as an important method to interpret present and past environmental conditions. However, few studies on shark teeth have focused their attention on making trophic inferences or reconstruction of diet. METHODS We analyzed the carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope composition of the tooth crown and root from blue sharks Prionace glauca caught in southern Baja California using a continuous-flow system by means of an elemental analyzer combined with a Delta Plus XL mass spectrometer, to describe their feeding ecology, considering sex and maturity stage. RESULTS Significant differences in δ¹³C values for tooth root were found between immature and mature males, with depleted values of ¹³C in immature individuals. No statistical differences were found between maturity stages in females for both the C and N isotopes in any part of the tooth, which suggests that females were consuming the same prey in the same area. In addition, we observed significant differences in δ¹⁵N values between the tooth crown and root. CONCLUSIONS Isotopic analysis in the tooth crown (dentin) and root may represent a new tool to describe the feeding ecology of different species of elasmobranchs, showing dietary change over a short timescale.