An Assessment of Calcified Structures for Estimating Northern Pike Ages

An important component of effective fisheries management is estimating fish ages. Age estimates can be used to estimate recruitment, relative abundance of age-groups, total mortality, and growth. Because of difficulty in estimating Northern Pike Esox lucius ages using scales and whole cleithra, we compared precision and bias of age estimates from whole cleithra, sectioned cleithra, metapterygoid bones, otoliths, and scales. Metapterygoid bones and sectioned cleithra represent two novel structures for estimating ages in North America, and the assessment of otoliths is limited. Complete agreement and consensus agreement rates were greatest for otoliths, sectioned cleithra, and metapterygoid bones. Otoliths provided the most precise age estimates and whole cleithra were the least precise. Consensus age estimates for sectioned cleithra were lower than whole cleithrum estimates. Consensus age estimates from sectioned otoliths were lower than mean age estimates from scales, sectioned cleithra, and whole cleithra, and y-intercepts from the age-bias plots were significantly different than zero. We suggest that otoliths, sectioned cleithra, and metapterygoid bones can be used to estimate Northern Pike ages, but recommend the use of sectioned otoliths because they had the highest precision and otoliths have become a common means of estimating ages for many species.