Effects of skeletal element identity, delipidation and demineralization on the analysis of stable isotope ratios of C and N in fish bone

Stable isotope ratios of C and N in the bone tissue of three different skeletal elements (angular, cleithrum and vertebra) of three fish species from different evolutionary lineages (Clupeiformes, Atheriniformes and Notothenioidei) were determined before (δ 13 C bulk and δ 15 N bulk ) and after demineralization and delipidation (δ 13 C dml and δ 15 N dml ). One of the species had cellular bone and the other two had acellular bone. Results revealed that δ 15 N and δ 13 C values from different skeletal elements were interchangeable in species with acellular bone, but caution was needed in species with cellular bone, as δ 15 N values varied among skeletal elements. Furthermore, δ 15 N bulk values were significantly lower than δ 15 N dml values in the three species, thus suggesting that they are not comparable. This difference is probably because δ 15 N bulk refers to total bone protein and δ 15 N dml to collagen only.