Species-specific variation in cuttlebone δ13C and δ18O for three species of Mediterranean cuttlefish

Stable carbon (δ13C) and oxygen (δ18O) isotopes in cuttlebones of three species of Mediterranean cuttlefish (Sepia elegans, S. officinalis, and S. orbignyana) with different life histories were contrasted. Cuttlebone δ13C and δ18O were quantified at both the core and edge (representing early life and recent deposition, respectively) for all three species sampled from the southern Adriatic Sea in 2010 (n = 28). For S. officinalis, cuttlebone δ13C and δ18O values were both lower relative to S. elegans and S. orbignyana at the core by approximately 1.0–2.0 and 3.0 ‰, respectively. Differences between core and edge in cuttlebone δ13C and δ18O were also observed for S. officinalis with observed values at the cuttlebone edge (recent) exceeding core (early life) values by 2.5 ‰ for δ13C and 1.4 ‰ for δ18O. Differences in isotopic composition across S. officinalis cuttlebones are possibly reflective of ontogenetic migrations from nearshore nurseries (lower seawater δ13C and δ18O values) to offshore overwintering habitats (higher seawater δ13C and δ18O values). Overall, results from this study suggest that cuttlebone δ13C and δ18O hold promise as natural tags for determining the degree of spatial connectivity between nearshore and offshore environments used by cuttlefish.