Precision and Bias in Aging Northern Pike: Comparisons among Four Calcified Structures

Abstract

AbstractAge estimates based on calcified structures are central to the analysis and management of fish populations. A variety of structures have been used in studies of Northern Pike Esox lucius despite limited data on whether the structures provide comparable results. We quantified precision and bias of ages estimated from cleithra, otoliths, anal fin rays, and scales of Northern Pike sampled in tributaries of Green Bay, Lake Michigan. For three independent readers, the precision (CV) of age estimates did not significantly differ among otoliths, cleithra, and anal fin rays but was significantly lower for scales than for the other structures. Similarly, partial agreement among readers was greater than 90% for ages estimated from otoliths, cleithra, and anal fin rays, whereas partial agreement was 76% for scale‐based ages. We discuss the tradeoffs associated with precision and bias for each structure in the context of reader experience, fish age, and management goals. We recommend that when fish mortality is not a concern, otoliths or cleithra should be used to achieve high‐precision aging of Northern Pike. For strictly nonlethal sampling scenarios, the anal fin rays of Northern Pike will yield more precise age estimates than scales.Received January 20, 2015; accepted September 17, 2015