Validating daily age via lapilli otolith growth rings in larval Grass Carp Ctenopharyngodon idella

Accurate age estimation is crucial for understanding fish population dynamics, yet daily age validation for invasive Grass Carp in the Midwestern U.S. is lacking. We validated daily otolith increment deposition in known-age Grass Carp reared in laboratory and pond environments. Larval Grass Carp from captive broodstock were sampled between 6- and 120-days post-hatch. Lapilli otoliths were extracted, lightly sanded, and read three times to estimate age, in days, which was compared against known age. Daily increment deposition was validated through 51 days post-hatch for tank-reared fish and 69 days for pond-reared fish, indicating lapilli otoliths can provide reliable daily age estimates for early life stages of Grass Carp.