Stable isotopes provide evidence of a trophic shift in the lesser spotted dogfish Scyliorhinus canicula from the Central Tyrrhenian Sea

Stable isotopes (delta 13C and delta 15N) were analysed in vertebrae of Scyliorhinus canicula (n=40; 13 males, 27 females) from the central Tyrrhenian Sea to explore a potential trophic shift in relation to sex and maturity condition. Isotopic values were obtained from the centre and the periphery of the vertebra of each individual to test for the effect of maturity condition. The values of delta 13C and delta 15N showed significant differences between the immature and mature state of the individuals analysed (U'=1392, P<0.0001 for delta 13C; U'=1385, P<0.0001 for delta 15N). Differences in values of delta 15N demonstrated a trophic shift during maturation progress of S. canicula. The peripheral vertebral part, corresponding to the mature state of each individual, showed higher values of delta 15N (mean 5.41 parts per thousand SD +/- 1.29 parts per thousand), compared with the lower values of delta 15N (mean 2.78%0 SD +/- 1.52%0) observed in the central vertebral part related to the immature state. In contrast, the isotopic signature of delta 13C was lower in the vertebral centra, and thus related to areas less enriched in C13 (mean -22.56%0 SD +/- 1.26%0) in comparison with the vertebral periphery (mean -20.03%0 SD +/- 1.34%0) linked to more productive environments. No significant differences in delta 13C or for delta 15N values were observed between sexes.