Applicability of Non-Lethal Aging of Fish Species at Risk in Canada

Confidently aging fish species at risk using non-lethal sampling techniques is critical to the understanding and management of these species. Knowledge of population age structure can be used in the determination of population extinction risk, and can inform decisions on allowable harm.  Age interpretations results from various aging structures can be compared to determine if ages obtained from scales can be used as an accurate age indicator for small-bodied fish species at risk. This study focuses on structural age comparisons of two species at risk in Canada; Grass Pickerel (Esox americanus vermiculatus) and Silver Shiner (Notropis photogenis). To determine if age interpretations from scale samples can be used as a viable method of non-lethally aging of small-bodied fishes, ages derived from scales were compared against cleithra extracted from the same specimens of Grass Pickerel, and otoliths extracted from the same specimens of Silver Shiner. A comparison of age interpretations from the Silver Shiner samples indicate that scale samples may not be a viable method because differences in age interpretations on both structures from individuals can vary considerably, while the Grass Pickerel scale samples may be used as a viable method of determining age of individuals.