Abstract
The increment deposition rate in sagittal otoliths of larval and juvenile summer flounder, Paralichthys dentatus, was influenced by growth rate. Larvae of known age showed less-than-daily increment deposition during slow growth (0.1 mm∙d−1), but increment deposition appeared daily after the growth rate increased to 0.4 mm∙d−1. There was no significant difference between counts from larval otoliths made by either scanning electron microscopy or light microscopy. Juveniles collected in the field that were tetracycline marked and held in the laboratory at elevated temperatures (≈15 °C) showed significantly faster growth rates (0.3 mm∙d−1) and daily increment depositon rates compared with growth rates (−0.03 mm∙d−1) and less-than-daily increment deposition rates at ambient temperature (1–11 °C). Tetracycline-marked juveniles, held in cages in a subtidal creek, also showed daily increment deposition. Scale circuli were not deposited daily in the juveniles examined. It appears that daily aging of the youngest P. dentatus larvae is problematic, but after settlement in estuarine nursery areas, increment formation occurs daily.