Marking Otoliths by Immersion of Marine Fish Larvae in Tetracycline

Otoliths of the larvae of spot Leiostomus xanthurus and pinfish Lagodon rhomboides were marked with a band that fluoresced in ultraviolet (UV) light after live larvae had been immersed for 1–2 hours in tris-buffered, 100–500-mg/liter solutions of tetracycline in a 1% NaCl solution. Dimethyl sulfoxide did not significantly increase tetracycline uptake. After otoliths were marked, their radii increased approximately 18% in 8 days for spot and 15% for pinfish, but distinct daily growth increments could not be detected even though diel periodicities in feeding and photoperiod were provided in the laboratory.