Interactive effects of age and environmental modifiers on the production of daily growth increments in otoliths of plainfin midshipman, Porichthys notatus.

Daily growth increments were formed upon hatch unless a diel photoperiod was absent, but under constant light, an endogenous circadian rhythm became evident after 2-3wk acclimation, resulting in daily increment production. With increasing age, the influence of light as a Zeitgeber decreased, while daily increments became more prominent in all environments. Temperature fluctuation affected increment appearance, but did not entrain increment deposition.- from Author