Daily Growth Increments in Otoliths of Starry Flounder (Platichthys stellatus) and the Influence of Some Environmental Variables in Their Production

Abstract

Tetracycline injected into juvenile starry flounders (Platichthys stellatus) was incorporated into the periphery of the sagittal otoliths within 24 h. The resulting band, visible under ultraviolet light, was used as a dated mark on the otolith growth increments. This technique was used to verify that increments were laid down on a daily basis, both in field and laboratory environments. Subdaily increments were visible in otoliths of fishes reared under most environmental conditions. The production of daily increments in juvenile starry flounders preconditioned to a natural environmental regime was unaffected by photoperiod or temperature fluctuation, suggesting the presence of an internal circadian rhythm.Key words: starry flounder, Platichthys stellatus; otoliths, daily rings, growth increments, circadian, tetracycline