Use of Regenerated Scales and Scale Marginal Increments as Indicators of Recent Dietary History in Fish

The potential of teleost scales as indicator tissues of recent dietary history was investigated in the estuarine fish, Notolabrus celidotus. Treatment fish were fed a ¹⁵N-enriched bivalve diet (δ¹⁵N = 108.8‰) for up to 90 days to examine integration of the dietary source signature in scale margin, regenerated scale, and dorsal muscle tissues. Regenerated scales exhibited the greatest and most rapid enrichment in δ¹⁵N (to 53.4 ± 5.0‰) of the tissues examined. Scale margin δ¹⁵N signatures also increased significantly from 14.5‰ to 30.9 ± 6.0‰, while muscle tissue only increased by 2.8‰ after 90 days. Dietary contribution models suggested that isotopic equilibration of dietary nitrogen would be most rapid in regenerated scales, followed by scale marginal increments and then muscle. In conclusion, teleost scales hold considerable potential as novel, nondestructive indicators of recent dietary history, yet currently face constraints from uncertainties in isotopic integration mechanisms.