Feeding periodicity and the production of daily growth increments in otoliths of steelhead trout (Salmo gairdneri) and starry flounder (Platichthys stellatus)

Abstract

Juvenile steelhead trout (Salmo gairdneri) and starry flounders (Platichthys stellatus) were reared 64–76 days under various experimental feeding regimes to determine if feeding periodicity influenced the production of daily growth increments on the otoliths. Both species produced daily increments when fed thrice daily, daily, or once every 3 days, as well as through 26–32 days of starvation. Daily growth increments were also deposited in vateritic ("crystalline") otoliths, which constituted 27% of the trout sagittae sampled. Feeding frequency affected increment appearance and the incidence of subdaily increments in trout, but not in flounders. The difference in effect was probably due to the higher metabolic rate of trout. Increment deposition in all flounders was far more variable than in trout, and some flounders apparently ceased increment formation altogether.