Trophic inferences of blue shark (Prionace glauca) in the Mexican Pacific from stable isotope analysis in teeth.
BACKGROUND
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 (δ(13)C) and nitrogen (δ(15)N) 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 δ(13)C values for tooth root were found between immature and mature males, with depleted values of (13)C 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 δ(15)N 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.
Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, México, D.F., México.
Carlos J
CJ
Polo-Silva
Felipe
F
Galván-Magaña
Antonio
A
Delgado-Huertas
D000818:Animals; D002247:Carbon Isotopes / Q000032:analysis* / Q000378:metabolism; D005260:Female; D020387:Food Chain; D008297:Male; D008386:Marine Biology; D008800:Mexico; D009587:Nitrogen Isotopes / Q000032:analysis* / Q000378:metabolism; D012754:Sharks / Q000254:growth & development / Q000378:metabolism*; D014070:Tooth / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes