Correlation between δ¹³C and δ¹⁵N in flying fish (Exocoetus volitans) muscle and scales from the South China Sea

We collected flying fish (Exocoetus volitans) from the South China Sea to determine whether fish scale isotope values correlate with those from muscle, and discuss relevant eco-environmental implications. A significant positive correlation was determined between fish scales and muscle δ¹³C and δ¹⁵N, rendering a fish scale an alternative to muscle tissue for stable isotope analysis. However, muscle and scale isotopic offsets should be fully considered when using δ¹³C and δ¹⁵N to analyze the actual trophic level of fish and their food source. The average offsets of δ¹³C and δ¹⁵N between muscles and scales are -2.1 ± 0.5‰ and 2.3 ± 0.6‰, respectively, though these values vary slightly with fish mass. Weak correlations were found between δ¹³C and δ¹⁵N, both in the flying fish muscle and scales, suggesting that other factors are influencing δ¹³C and δ¹⁵N. Fish δ¹⁵N also correlates with the size of individuals, while δ¹³C reflects the marine habitat. Based on our data, it appears that more eco-environmental processes can be revealed from modern or ancient flying fish scales.