Supplementary material from "Regional patterns of δ¹³C and δ¹⁵N for European common cuttlefish (Sepia officinalis) throughout the Northeast Atlantic Ocean and Mediterranean Sea"

Stable isotope compositions of carbon and nitrogen (expressed as δ¹³C and δ¹⁵N) from the European common cuttlefish (Sepia officinalis) were measured in order to evaluate the utility of using these natural tracers throughout the Northeast Atlantic Ocean and Mediterranean Sea (NEAO-MS). Mantle tissue was obtained from S. officinalis collected from 11 sampling locations spanning a wide geographical coverage in the NEAO-MS. Significant differences of both δ¹³C and δ¹⁵N values were found among S. officinalis samples relative to sampling location. δ¹³C values did not show any discernable spatial trends; however, a distinct pattern of lower δ¹⁵N values in the Mediterranean Sea relative to the NEAO existed. Mean δ¹⁵N values of S. officinalis in the Mediterranean Sea averaged 2.5 ‰ lower than conspecifics collected in the NEAO and showed a decreasing eastward trend within the Mediterranean Sea with the lowest values in the most eastern sampling locations. Results suggest δ¹⁵N may serve as a useful natural tracer for studies on the population structure of S. officinalis as well as other marine organisms throughout the NEAO-MS.