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Age 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

Successful fisheries management practices developed for one ecosystem can often be used in similar ecosystems. We developed a flexible lake classification framework in collaboration with ~100 fisheries biologists for improved fisheries conservation management in Wisconsin, USA. In total, 5,950 lakes were classified into 15 lake classes using a two‐tiered approach. In tier‐one, lakes were clustered into “simple” and “complex” sportfish assemblages. In tier‐two, lakes were further clustered using accumulated degree days, water clarity, and special cases. We focus on temperature and clarity because these factors often drive fisheries change over time—thus a lake's class can change over time. Lake class assignments were refined through a vetting process where fisheries biologists with expert knowledge provided feedback. Relative abundance, size‐structure, and growth rates of fishes varied significantly across classes. Biologists are encouraged to utilize class interquartile ranges in fisheries metrics to make improved fisheries assessments. We highlight hard‐won lessons from our effort including: (1) the importance of co‐developing classification frameworks alongside fisheries biologists; and (2) encouraging frameworks where lakes can shift classes and fisheries expectations over time due to factors like climate change and eutrophication.

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