Cooperative Fish and Wildlife Research Units Program: Oklahoma
Education, Research and Technical Assistance for Managing Our Natural Resources

Accurate age and growth information is essential in successful management of fish populations and for a complete understanding of early life history. We validated daily ring formation, including the timing of first ring formation, for Spotted Gar (Lepisosteus oculatus), a species of conservation concern, through 127 days post-hatch. From fry produced from hatchery-spawned specimens, up to 10 individuals per week were sacrificed and their otoliths (sagitta, lapilli, and asteriscus) removed for daily age estimation. Daily age estimates for all three otolith pairs were significantly related to known age (r² ≥ 0.95), but the strongest relationship existed for measurements from sagittae (r² = 0.98) and the lapillus (r² = 0.98). Age prediction models all resulted in a slope near unity, indicating that ring deposition occurred approximately daily. Timing of ring formation varied among otolith types; sagitta approximately 3 days after hatch, lapillus 7 days after hatch (i.e., swim-up), and asteriscus 9 days after hatch. These results fill a gap in knowledge and can aid understanding of evolutionary processes as well as provide useful information for management and conservation.