Daily Increment Formation in Otoliths of the Redspotted Sunfish

Abstract

To generate reliable age information for fishes, we must assess the robustness of techniques to environmental variation. We quantified daily ring deposition within the sagittal otoliths of known-age larval and juvenile redspotted sunfish Lepomis miniatus reared in ponds. We also determined how daily light : dark cycles mimicking natural conditions, reduced daylight, or constant daylight affected ring deposition in fish housed in aquaria. Additionally, we quantified how constant temperature (26°C), low daily variability in temperature (26±1°C), and high daily variability (26±2°C) affected production of daily rings. In pond-reared fish, the first increment was produced by the evening of hatch, and increment deposition occurred with 24-h periodicity through 119 d. Independent age estimates from two readers closely agreed. Photocycle and temperature variation did not affect periodicity of increment formation or the precision and accuracy of age estimates. Age and growth data can be reliably determined in this species to assess recruitment dynamics and develop management and conservation strategies.